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Compendium for digital photography

ImageEngineering

English translation sponsored by:

COMPENDIUM FOR DIGITAL PHOTOGRAPHY


A cooperation o :


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Dear readers.

The "Compendium or digital photography" aka. "DigiPix" in version3 was originally written and published November 2004 in and by thecooperation o the ad (Working Group Digital Photography) and theECI (European Color Initiative) - in german only. With the kind o posi-tive acceptance we received in public the idea o an international ver-sion available in english was soon born and eventually realized. Dueto the ast paced innovation in the eld o digital photography anddigital imaging in general some areas o this guide are not up-to-datewith the latest and greatest. An updated version will be available inthe near uture.Meanwhile the authoring team hopes to provide you, the photog-rapher with a batch o tips and help ul background in o, in order tomake your daily digital job a lot easier.

I would like to thank the sponsors, Image Engineering Dietmar Wller,Tecco Braun & Frings GmbH and LaserSo t Imaging AG or making thistranslation possible through their much appreciated support.

We wanted to make sure that this publication can be used as reely aspossible which is why we issued CREATIVE COMMONS PUBLIC LICENSEat the end o this document. We the authors expect the compliancewith it.

Jan-Willem Rosse September o 2006([email protected])

The authors:

ad (workingroup digital photography):Reinhard Fittkau, Holger Hagedorn, Dirk Hartmann, Dr. Martin Knapp,Matthias WeiseECI:Dieter Dolezal, Dietmar Fuchs, Jan-Willem Rosse, Andre Schtzen-ho er, Dietmar Wuellerweitere Autoren:Ulrike Haessler, Christian Westphalen

Preambel


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Preamble 2Content 3

1. Color management 41.1 Basics color management 41.2 Pro ling a digital camera 81.3 Working spaces 131.4 Viewing conditions 181.5 Visualization on the monitor 201.6 Visualization in print 241.7 Settings in Photoshop 27

2 Photography 362.1 Exposure and lighting 362.2 Formats, color depth and compression 392.3 Resolution 432.4 In-camera sharpening 482.5 Color space 502.6 White balance 542.7 Storage media 562.8 Camera maintenance 58

3. Data optimization 633.1 EXIF 633.2 IPTC 643.3 Description - Naming conventions 65

4 Processing data 674.1 Importing and processing raw data 674.2 Tonal range levels and contrast adjustments 734.3 Adjusting resolution 78

4.4 Additional sharpening 795. Interchange ormat or the trans er o data 815.1 Recommended le ormats 815.2 Communication trans er 86

6. Application speci c considerations 896.1 Photojournalism 896.2 Portraiture photography 926.3 Advertising photography 94

7. License 97

Content


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The overlapping communication o color according to ICC-Stan-dard is todays oundation or color management in a media pro-duction environment. Applied color management will bringpredictability and consequently security along into the colorworkfow, rom data input to conversion and output processing.

What is the undamental challenge o color management within theboundaries o physics:

- make the scan look like the original on the monitor- make the print look like the original on the monitor- make the print o a scan, without much examination on the monitor,look very similar to the original- generate veri cation or images to look similar on di erent machinesand monitors

Ten years a ter its introduction the vendor and plat orm independentICC-Standard has reached a high pro essional level and creates thebasis or an e cient color management system, in combination with aprogressive hard- and so tware development.The entire communication o color in a modern production environ-ment is going through a stage o modi cation, which yet alreadytakes place during photography due to the increased commitment todigital photography. Whenever precise color reproduction is manda-tory especially when shooting in a studio color management canbe applied in digital photography as such. When shooting outdoorsthe vendors color trans ormations inside the camera will seize, or theuser color management starts once the nal image will be displayedon the monitor.

Working environment, general set-up

ICC Pro les which characterize the color reproduction o a certaindevice are being used in a controllable and sa e process with imagedata in order to transport color in a production process. The ICC speci-

es device pro les (ICC pro les) and the mapping o the color engineused, which realizes a consequent color management rom photogra-phy to print respectively displaying the images on the monitor.The actual photography is very o ten the source or color data, hence

in the beginning there is the digitalization o a subject respectivelya scene or a scan. A modern working environment is based on the

1. Color management

1.1 Basics Color management


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digital capture and reproduction o originals with a device or so t-ware which supports color management and implements itsel intothe workfow harmoniously.

Basic principles o color management / Conversion with ICCpro les

Communication in a standardized language is crucial or any kind omanagement. Based on human color vision and comprehending all vi-sual colors the device independent "CIE-L*a*b*" (see end o chapter)color model is used as a standardized language, which describes anequidistant color space based on human color reception. This is thebasic principle o color management.

Any input- and output device participating in the production process(digital camera, scanner, monitor, printer, etc.) eatures an individualcharacteristic way o color reproduction and describes a portion othe colors which are visible or humans. This portion, which is beingre erred to as "device color space", is visualized three dimensionallyas CIE-L*a*b* color space in the graph-ic below. In order to transport color ina standardized, comprehensive andunique way through the productionprocess, ICC pro les o every single de-

vice have to be created. The ICC pro leestablishes the connection between theaccording device dependent characteris-tic (device speci c RGB or CMYK) and thedevice independent characteristic CIE-L*a*b* - in other words: The individualcolor idioms o the individual input- andoutput devices are translated into a mu-tual language. Due to the act that thepro le captures only a certain amounto colors, an extra engine the so calledCMM (Color Management Module) is necessary or the calculation othe secondary tonal values, one o each operation system, Apple andMicroso t, already has one built in.

Due to the mutual language within the ICC pro les it is now com-monly de ned, how certain devices see and reproduce certain colorvalues. There ore single colors as well as complete images can be pro-cessed and controlled as requested. For this purpose the ICC pro les,the CMMs and their implementation into the applications will mergetogether and result in a color management workfow, in cooperation


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with the special retouching-, editing- and proo ng unctionality.

Basic principles or data management / Workfow with ICCpro les, Inter aces

From the photographers view as the "data originator" data pro-cessing and distribution in RGB is the better option, which onewhile retouching can all back to so tproo unctionality i desiredor requested in order to simulate the nal output- or printed re-sult. Needless to say the nal output system needs to be amiliar.

The input data is in relation to the complete workfow resembled asdigital photographs or scans, which will eventually get edited and

trans erred either directly or a terwardsin company with graphic- respectivelytext elements into a layout applicationlike Quark Xpress or Adobe InDesign inorder to be optimized and exported intothe nal output process.

The photographer will initiate thecommission o data according to thestatus o an image either to the post-production or prepress inter ace.

The color- and process related optimi-zation o data to the according outputprocess (in a normal case the separation

rom RGB to CMYK) )can occur at di er-ent sets o the workfow, while one generally needs to di erentiatebetween the process independent and process dependent approach.

The output optimization (separation) needs to take place at the endwhen applying a medianeutral workfow and data managementwhich itsel will generate per ect premises or the optimization to

urther output processes. When choosing a process dependent ap-proach the optimization respectively the commitment to speci edoutput conditions will occur at an earlier stage in the workfow.

Both workfow options eature their advantages, with thepossibility or an optional hybrid approach at a later time.To which extent the photographer will per orm the output optimizationneeds to be decided upon individually and to the standard o knowledge.It shouldn't be regarded as the one primary exercise or the photographer.

The so tproo -visualisation displays a pre-view o the printed output "on-the- y".


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The integration o ICC color management to a working environ-ment supplies these possibilities. Color management can make ac-cess to generic or idealized color spaces or process descriptionslike ECI-RGB, ISOcoated, PDF/X,..... or depend upon adaptions

o special devices via individual ICC compatible procedures.

As one important component o workfow and data management, ap-plied color management can sa eguard adequate fexibility and securityto the according inter aces, much as the trans er o image material ophotographers to postproduction / prepress. It greatly matters to save thecurrent description o color in the shape o an ICC pro le to every image.

(*) CIE = Commission Internationale de lEclairage. De ned in 1931 theXYZ-color model and subsequently urther standards, or example the

amiliar CIE-standard color chart, known as the sole. This de nition isbased upon results o the latest research, rom which a "standard ob-server" was de ned. This standard observer complies with 90% o thecolor reception o humans. In 1976 the CIE-Lab color space was intro-duced by the CIE, which in contrary to the "sole" had the advantageo the calculative o set similarity.


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1.2 Pro ling a digital cameraAdvantages o camera pro les

The advantage in the application o individually created camera pro-les lies within the compensation o "color-ametropia" ( ailure o vis-

ibility) o colors, which is inherent in any digital camera. The color-ametropia di ers rom vendor to vendor as will discrepancies occurbetween one vendors camera models. Through the use o camerapro les the photographer has more security, as a more precise colorreproduction rom one camera as well as many di erent cameras,instead o having to pass through long editing cycles in image editingapplications. Ultimately the use o camera pro les reduces the hourso work per image and there ore increases productivity.

Camera pro le, more than a digital emulsionThrough the application o camera pro les a digital camera is muchmore quali ed or the precise reproduction o colors than the ana-logue lm ever has been.Just like the lm emulsions in analogue photography were designed

or di erent types o light it is essential or camera pro les to be op-timized or one type o light and should be applied with this only.While in analogue photography the applied daylight- or tungstenlight lm in contrary to the used camera and optics displays themost important parameter or color reproduction, the used cameraand processing technology and urther workfow inside the cameraplays a major role, i.e. inside the raw data converter or color re-production, which has to be incorporated when creating a pro le.Thus the camera pro le describes the characteristic o a camera withcertain light as well as the adjacent camera- and data processing.Furthermore not only daylight- or tungsten customizations can be re-alized via camera pro les, but as many "Illuminant-pro les" as needed

or photographic work, i.e. a pro le or HMI- or fuorescent tubes. Thepro le can be applied to similar light types again and again just likedaylight or tungsten lm in analogue photography. For example a pro-

le created or fash light in many cases can be applied on a daylightlocation, when using the white balance unctionality inside the cam-era. This operation method will save the photographer a lot o e ortinstead o having to create a new pro le or every new composition.Pre erably the camera pro le should only incorporate an exposure-or contrast adaptation, i necessary due to insu cient exposure orgradation when taking the photo. The correct exposure and choiceo gradation will remain the photographers responsibility, just like

selective application o white balance. So mainly the camera pro le issupposed to correct the color reproduction o a camera.


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Range o application or camera pro les

This preliminary remark about the advantages o camera pro les al-ready indicates the range o application o such camera pro les. Theapplication o camera pro les plays a vital role whenever an exposuredepends on exact color reproduction. This could be art reproductions,table-top and studio photography and whenever there is an increaseddemand in color reproduction, e.g. or a corporate-, logo- or productcolor. In photo journalism, where it is all about speed and changingrecording condition, in artistic photography as well as generally whendisposing a mood or eeling, color does represent a vital role, but theprecision o color plays an rather in erior role. In these cases the use oindividual camera pro les is not categorically mandatory and due tothe customization o the workfow partly obstructive.

Creation o pro les

So tware and adequate test charts:When creating camera pro les special test charts are necessary besidesthe pro ling so tware in order to capture the color characteristics othe camera.In principle the best test chart or this purpose is dependent on thepro ling so tware. The most commonly distributed test charts or pro-

ling cameras are rom Gretag Macbeth. For one thing the DigitalColorCheckerSG and the ColorCheckerDC as well as the ColorCheckerwith 24 color patches can be named here, whereas the ColorCheck-erSG gathers the color characteristics o the camera best due to itsmaterial properties. Some pro ling packages also use test charts pro-duced on glossy photographic materials with additional greycards ondi ering materials and can create good results. IT8 test charts used orpro ling scanners are unquali ed or pro ling cameras. It is important

or the appropriate test charts to o er a good share o bright, semibright and dark colors, no optical brighteners as well as eature highlysaturated colors and there ore represent a

large color space. On the other hand thecolors are supposed to ll in the color spaceconsistently and a neutral grey balance (nocolor cast under certain types o light) ordetermination o the grey balance, whichwill represent the grey characteristics o thecamera. A duller patch will prevent glossylike refections o light more likely whereason the other hand the color characteristicso the camera with highly saturated colors

can not be captured satis actory. Hence asemi matte material is a good compromise.The Color Checker SG rom GretagMacbeth


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Pro ling so tware should be able to operate according to most recentICC speci cations and use chromatic adaption a ter Brad ord (math-ematical unction to adapt data to di erent light types) or newermethods. The so tware needs to support di erent types o light and i

applicable add user-oriented types o light. Grey balance needs to beable to operate in two di erent settings: choose a grey balance whichis calculated automatically rom the so tware based on the data romthe test chart or not to a ect the grey balance setting in the camera.

In addition the camera pro ling so tware needs to leave some optionsto the user, in order to customise the pro le according to individualrequirements. Just as di erent lm types were used in analogue pho-tography in order to achieve per ect skin tones or example, the pro-

ling so tware should o er the opportunity to customise a camerapro le in relation to the sole purpose o its use.

Capturing the test chart and exposure

The most success ul way to create a camera pro le is to shoot thetest chart under repro illumination and pre erably record withmaximum bit depth. This means to place the light source pre er-ably two heads rom le t and right - in a 45 angle to the cameraand to the test chart, in order to illuminate the chart as plane andevenly as possible. The ideal condition or capturing the test chart is

a darkened room with no disturbing refections on the chart as wellas light source with constant temperature, illumination o light andequal brightness. Likewise the test chart can be captured outsidethe studio as well i disturbing re ections and mirroring can be pre-vented. Refections can be minimized by underlaying or hanging amatte black or grey piece o cardboard or cloth o adequate size.

The right exposure or the test chart is essential or the success o apremium digital camera pro le. I the exposure o the test chart isdarker than that o the images you will be taking, the pro le will

make the images look much brighter. In reverse a brighter expo-sure o the test chart will end in a darker reproduction o your im-ages. The correct exposure should best be determined by a row oexposures. A re erence value or the correct exposure when usingthe Gretag Macbeth test charts can be checked upon by the whitetest chart patches. The patch should keep lower RGB values thanthe white areas o your image with just as little detail as possible.When using premium studio cameras the right exposure o the testchart should result in RGB values rom 235-245 in the white patches.For SLR and range nder cameras a good starting point or the rightexposure o the test chart is measuring a greycard (e.g. the Kodak-


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greycard) and trans erring the exposure values to the test chart shot.

Since color-ametropia shows di erent e ects with di erent lightingconditions, it would be sel -evident to place the test chart directly into

the scene to be photographed and create the pro le rom there. Prac-tical experience shows little success or this approach. The illuminationo the scene very o ten leads to e.g. black patches o the test chart tobe too light as a result o direct refections o a light source and there-

ore will create errors in the pro le. The same is obviously true orthe patches that refect directly into the direction o the camera. Addoccurring alsi cation o colors to this, due to refections o coloredobjects in the scene. For example, when shooting a tabletop setup ona colored underground, the refections o the underground will inter-

ere and lead to alsi ed colors in the test chart and to bad pro les.Likewise with refections o metal objects or white walls which caninfuence the capturing o the test chart in a negative way.

White balance

A correct white balance is one o the most essential requirements or agood pro le as well as the subsequent application o the pro le. Thewhite balance can be comprehended as a calibration o the camera tothe according lighting conditions. It must be pointed out that someSLRs and Range nder cameras will accomplish the white balance by a

white area. I using an improper material like a piece o paper or thisit may lead to drastic errors in the pro le due to optical brighteners inmany papers. An alternative or the correct white balance with a larg-er, neutral area is the use o the Gretag Macbeth White balance Card.The predominant portion o cameras will acquire white balance oa neutral grey area. There are ull- ormat greycards available on themarket or this. A Kodak greycard with its 18% refection is very ap-propriate or exposure metering, but not or white balance, since it isnot su ciently neutral.

Depending on the camera the greycard needs to be captured ull- rame.The grey patches o the camera chart can be utilized or white balanceas well or more premium cameras. Double check the white balance inthe image via the pipette o your image editing application or the rawdata converter. A success ul white balance will avour an interpretationo the camera o neutral grey areas in the image with equal RGB values.

I the white balance, the exposure and the illumination o the testchart have been per ormed according to these instructions, then youhave made a oundation or a good camera pro le. Please considerduring the application o the camera pro le that the pro le will oper-


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ate reliably just as long as the basic settings in the camera respectivelyin the urther editing workfow are maintained between the imagecapturing and the capturing o the test chart. I e.g. switching theraw data converter, the pro le created with a di erent converter can

not be applied anymore. Furthermore, always keep in mind to doublecheck white balance as an essential quality eature during image cap-ture and modi y it i necessary, then you are on the sa e side, to usethe one-time created camera pro les or a lot o shots.


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In image editing applications the e ect o certain tools on image datais infuenced by the color mode used one reason to look into color

modes and color spaces a little closer.It is an interesting experiment to per orm the same adjustment o im-age contrast once in RGB, CMYK and Lab. When increasing the con-trast o the image a little by lowering the shadows and raising thehighlights you will be able to experience dedicated image materialpresumed the ollowing e ect:RGB color mode: saturation o colors is increased.CMYK color mode: saturation o colors is increased but color shi tingoccurs and the shadows will ade out.LAB color mode: no shi ting o colors but increasing contrast due to theseparation o the brightness in ormation rom the color in ormation.Besides the investigated e ects other actors need to be taken intoconsideration or the choice o the appropriate color mode. The con-version o data to CMYK (= separation) requires accurate knowledgeabout the nal print process and the necessary color removal. The useo LAB in turn will lead to loss o details with 8-bit color depth in criti-cal areas o the image; Furthermore some tools in e.g. Photoshop arenot even available in LAB color mode (e.g. selective color correction).It turns out that RGB color mode is the most reasonable one or edit-ing digital images.

From color mode to color space ...

It seems even more con using since there is a multitude o color spacesavailable or the RGB color mode. A color space is a certain RGB de-scribed by means o an ICC pro le. At the beginning o the job the user

aces the challenge o choosing the correct color space or the captur-ing, editing and archiving o their images. The color space chosen orthe editing o the image (image retouching, image enhancements,unsharpmasking...) is being re erred to as a working space. (Attention:

Once again this is not the RGB color mode but a color space character-ized via an ICC pro le, e.g. eciRGB or AdobeRGB!) Prior to the decisionor a certain working space, some issues need to be considered.

Working spaces are described by the ollowing parameters:- the color values o the primary colors red, green and blue- the gamma value- the whitepoint

Primary colors

The de nition o the primary colors a ects the size o the color spacein the rst place. One needs to pay attention or a big enough result-ing color space or the desired output process, since during the cre-

1.3 Working spaces


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Appropriate working spaces

A brie while ago the European Color Initiative (ECI) aimed at the de-velopment o an RGB color space, which will cover the current estab-lished printing color spaces as good as possible, without becoming too"big". Since the Apple operating system took a commanding position,a gamma o 1.8 was chosen. As a Whitepoint D50 was speci ed andthe primary colors were ajared to the NTSC speci cations. The ECI colorspace is very well suited or editing, delivering and archival o imagedata, since the color space covers all current printing color spaces airlywell. ECI-RGB can be downloaded ree o charge rom the website othe ECI (www.eci.org). I you are working in an environment thoughthat does not support color management please bear in mind not touse any image data in eciRGB that has not been converted prior to

application. These are e.g. webapplications and O ce environments.For this purpose a conversion to sRGB be orehand is recommended.Another meaning ul working space is AdobeRGB, since it eaturesthe same gamma value as sRGB and some applications and cam-eras as well use it as a de ault setting. Especially with so twareproducts that do not attach color pro les we need to pay goodattention to the compliance o camera so tware working spaceand image editing working space. Additionally unnecessary col-or space changes should be prevented, since the loss o qualitydue to multiple conversions can not be eliminated to ull degree.(Note: Older Nikon digital-SLRs apply an in erior color reproduc-tion in AdobeRGB than in sRGB. In order to ensure a trouble-

ree workfow one should always conduct a number o colortests prior to switching the working space o the digital camera.)There is an interesting approach to this rom PhotogamutRGB (http:// www.photogamut.org/) The idea was trying to cover all current pho-tographic output- and printing processes and to eliminate all colorsnot contained rom this working space. On top o everything a har-monization with sRGB was aspired in order to reduce color alsi ca-tions due to the trans er o image data into a workfow without colormanagement. Please note the application o a so called LUT-pro le inorder to characterize this color space, which is over 150 kb in size andthere ore increases the le size to this amount. It has not spread inpractice so ar, but its de nitely worth keeping an eye on its develop-ment.

Special color spaces

We have not dealt with the extra big color spaces like CIE-RGBor WideGamutRGB up to this point. Those cover a visible range

as big as possible but should be applied in special cases only. Itmust be pointed out that the quality o a uture color separa-


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tion will be higher i the size o the working space and the desig-nated target color space will not di er signi cantly. Additional-ly these color spaces can not be displayed any more on a monitor.Note: It is not possible to display working spaces like eciRGB, Ado-

beRGB, PhotogamutRGB on a standard monitor at the moment. Thismeans it is not possible to visualize the di erentiations in highly satu-rated colors. Some special so tware applications or monitor calibra-tion o er a workaround (which can partly eliminate this drawback) aswell as some special monitors. These monitors have only been avail-able or a short while and distinguish themselves with a large colorspace besides a rather high price o cost beyond Euro 4.000,-.

Color spaces or Internet- and Consumer applications

When producing and editing data or in-ternet applications a very special approachhas proven itsel , which takes the peculiari-ties o Internet applications and "Consum-er monitors" and printers into account.Normally Web- and O ce applicationswill not support color management. Inorder to be able to communicate re-sembling colors to some degree, the IECwith the cooperation o some rather big

manu acturers (HP, Kodak, Microso t)speci ed the sRGB color space not so longago. Normally monitors and consumerdesktop printers are appointed to repro-duce the sRGB color space close enough.I images are placed in O ce documentsor in a web browser, a true-to-color re-production can be achieved best, i thedata has been characterized with sRGBas well. So there is the ollowing recom-

mendation or O ce- and internet appli-cations: Choose sRGB as output workingspace. This color is best suited or most

applications, which do not support color management, or exampleO ce so tware or generally the Windows operating system. In addi-tion many photolabs that o er the output o digital data on paperprints will not take attached ICC-pro les into account but simply as-sume that the data was processed to sRGB. Many digital cameras willproduce sRGB image data by actory de ault setting. Some more ad-vanced cameras will sometimes o er a di erent color space. It needsto be pointed out that the use o sRGB as a working space is not rec-

Comparison o color spaces:Yellow indicates Photogamut RGB, red ECI-RGB, grey and almost as big as ECI indicates

Adobe RGB and the smaller color space withins sRGB.


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ommended in a pro essional like environment, since sRGB describes arelatively small color space, leaving out some colors that can very wellprint in e.g. O set printing process (particularly in the Cyan range, butin yellow as well).

In Conclusion

There is no ideal working space or everything, but there is an appro-priate one or every intended application. In the premium prepressarea eciRGB is a good alternative, AdobeRGB is a well spread world-wide standard, which can already be provided by some input deviceslike scanners or digital cameras. But there are already some new inno-vative solutions emerging on the horizon, which will eliminate someo the disadvantages o todays well spread working spaces. Some ad-vice at last:1.) Exclusively use calibrated and pro led monitors or displayingyour images at all times and a so tware which supports color man-agement or displaying.2.) Stay well away rom editing in CMYK unless the client resists on it.3.) Always attach the ICC pro le used when saving the image data.4.) Pay attention when choosing your designated output space to becovered ully by your working space.


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It is due to the act that digital data can not be displayed without theaid o such devices as a monitor or printer, which makes calibrating

and pro ling the device used essential since data will not be displayedcorrectly otherwise.Just as important as the calibration and pro ling o these devicesare the viewing conditions under which the images will be viewed.It is rather clear that these conditions can not be ideal at all the times

or example or situations like in the area o photojournalism or whenshooting "on location". It gets rather important or the photographerto have the kind o experience at hand in these situations in order toestimate the kind o e ects these conditions will have on the imagedisplayed. This guide can not provide this kind o experience but itcan highlight the conditions, regarded as ideal when viewing images.Those o you wanting to take this one step urther can have a lookinto ISO 3664 (Viewing conditions Graphic technology and photog-raphy).

Walls and luminance

The walls should be painted either white or grey. A color ul paint-work or even colored foors need to be avoided. The luminance othe surroundings around the monitor should be according rom

60% to 10% o an white area on the monitor. Illumination needsto be as constant and even as possible. I daylight is used or il-lumination there needs to be some sort o protection rom directsunlight. Aluminum blinds are suited best or this purpose i theirlamellas are rotatable and arranged horizontally. The lamellas arecolor neutral and i using the appropriate angle the light can be di-rected to the ceiling and the amount o light can be adjusted. Thiswill provide the ideal illumination without disturbing refections.

Tip: Point a lightmeter with attached calotte to a white area on

your monitor and measure illumination. Than put the lightmeteragainst a white wall and measure the amount o light alling ontothe wall with the attached calotte (not the refecting light). Themonitor needs to be two -stops (range o 1-3 -stops is o.k.) brighter.

Try to avoid scattered light and direct refections on the monitor. This willwork best by attaching the lights (normlight fuorescent tubes) paral-lel to the window and equipped with glare shields. The monitor needsto be aligned parallel to the window area in order to prevent refec-tions and scattered light and should be equipped with a monitor hood.

1.4 Viewing conditions


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Tip:

I there was no such hood included with your monitor, you can custombuild one yoursel (make them 35 cm wide) with a couple o black ex-panded plastic slabs, available rom any specialized vendor or graphi-cal supplies, and attach them to the monitor with some velcro. Thecost adds up to something like Euro 3,- and they are just as good as the

ancy accessory rom the vendor.

Quality o light

Daylight is nice or illumination but it changes its color (spectral com-position) in relation to the weather situation and time o the day.Halogen lamps, light bulbsand regular fuorescent

tubes are not appropriateenough or the illumina-tion o an image editingworkstation. The illumina-tion o choice are fuores-cent tubes or standardizedlighting, thus fuorescenttubes with a spectral com-position, which gets veryclose to natural daylight. Itdoesnt have to be the ex-pensive special tube romthe manu acturers o view-ing boxes or proo ng purposes. The tubes rom Osram or Philipswill do the job very well and dont cost a lot more than a regulartube in the electronics department store. Look a ter the classi ca-tion rom Osram "Lumilux de Luxe xxWatt/950" and rom Philips"TLD de Luxe xxWatt 950". Thereby the most important criteria isthe 950 whereas the 9 stands or the highest quality o light and the

50 stands or 5000K. The power varies with the length o the tube.With the release o this guide Philips will bring a special TLD tube withthe classi cation TL-D 90 Graphica Pro, which can be recommended.

Those who need it precise can use a standardized color viewing box,available e.g. rom Just Normlicht, Kaiser Fototechnik or Mega Stahl.

One and the same color looks quite di erent under di erent viewing conditions. This is why the viewingconditions are so important.


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As a user we must not orget that we can not actually see digital imag-es with their "zeros and ones". We will always need an utility or the

visualization, like e.g. a monitor or a printer. We will never achieve acorrect presentation on the monitor i the utility has been misadjust-ed (like too dark or too contrasted). But what actually means a correctpresentation in this context?As a start we need to conceive the act, that a correct presentation odigital images is only possible when using image editing applicationsthat support color management according to ICC speci cations. Asdescribed in chapter 1.3, the image will be edited within a workingspace in this application. The description o this working space hasto be included with the image in the shape o an ICC pro le. The im-age editing application knows the color o each pixel rom the digitalvalue o each pixel and the according ICC pro le (discrepancies romcolor management modules and rendering intents are le t ignored atthis time). For the pixel to be presented correctly on the monitor, theimage editing application needs to know which digital value to sendto the graphics card, in order to create the same color. This occurslikewise via an ICC pro le or the monitor. The ollowing will describethe process o creating such a pro le.

Calibration o the monitor

First o all the monitor needs to be calibrated. What does that mean?A monitor that has been set e.g. too dark or too dull will never beable to display an image correctly. This means the monitor, in order todisplay as many colors as possible, needs to have a color space as big aspossible and needs to be adjusted per ectly rom the hardware side.Part o these optimum settings are besides the geometry, brightness,contrast and whitepoint in particular.While brightness and contrast can be checked with test images avail-able in tools like the DQ-tool rom the german association o photo

industries, on the ECI website or in so tware rom BasICColor or X-Rite,a spectralphotometer or at least a 3- or 4-range measuring device isnecessary to analyze the whitepoint.Also the presetting o the brightness characteristics, so ar this hasbeen called the gamma o the monitor, is part o the calibration pro-cess. This gamma is based on the mathematical description betweenthe interrelation o the input signal to the monitor in the shape ovoltage and the emitted amount o light (see link to Charles Poyton).Since this gamma will be managed rom the graphics card or the mon-itor electronics o modern computers/monitor, the usual principles arenot valid anymore or the control o todays LC-displays, the calibration

1.5 Visualisation on the monitor


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with the help o a gamma is currently replaced by a new optimized de-scription. The calibration towards a linear L* is being discussed in thiscontext. With this the L-axis (brightness-axis) o the Lab color spaceis meant, which describes the lightness reception o the human eye.

There ore the monitor should be set up as ideal as possible or thehuman eye with a calibration according toL*. I the so tware or monitor calibrationdoes not o er a way to calibrate accordingto L*, then a gamma should be chosen, thatcomes closest to the human perception andthat is a gamma o 2,2. This setting can beused on the Macintosh as well as on thePC. The historical reasons or setting theMacintosh Gamma to 1,8 came rom theprepress area and presently have no morerelevance.The choice o the whitepoint is anothercontroversial issue when calibrating a monitor. The ideal whitepoint isthe one that comes as close as possible to the regular viewing condi-tions or images. A study rom Kodak proves the spectral compositionindoors tends towards a color temperature o 5000K. In addition thereare special sources o light with a spectral composition based on thecolor reception o 5000K respectively a standardized light source withthe classi cation or D50. That means to set a whitepoint o D50 on themonitor. There is an exemption or CRT-monitors and especially oldermonitors which due to their light density contrast range will producea very yellowish presentation when choosing D50 as a whitepoint. Iyou have such a monitor, you better choose 6500K as color tempera-ture respectively the whitepoint o D65. An image, displayed on sucha monitor will come across a little bit cooler in direct comparison withthe original under D50 standardized light, but matches rather well tothe original relative to the white areas.The ideal settings or the monitor calibration are according to this:

check brightness and contrast with a test image or with the aid o ameasuring device.Choose the luminance characteristics i possible according to L*, oth-erwise choose gamma 2,2.Choose 5000K as a whitepoint and 6500K only in the mentioned ex-emptions.

Creating an ICC pro le

Subsequently to the calibration an ICC pro le has to be created or themonitor. This can be accomplished with the aid o a monitor measur-ing device and the according so tware. In the process o the pro le


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creation di erent colors will be displayed on the monitor and thenmeasured by the device attached to it. A pro le will be created romthe data collected and needs to be set as monitor pro le by de aultin the according operating system. Applications like Photoshop will

automatically apply the pro le in order to display the images correctlyon the monitor. Ever since Photoshop this can ortunately not get de-activated anymore and the user will always get the true-to-color pre-sentation, provided the color settings in Photoshop are correct (seechapter 1.7).

Take caution with Adobe Gamma and similar tools

In the past the premium quality measuring devices were rather expen-sive which is why there were some attempts to accomplish the calibra-tion o the monitor with the help o simple auxiliary tools. There oreAdobe o ered a small application called "Adobe Gamma" and Applewithin their monitor settings. These applications were operating by

the "rule o thumb" principle and a pro es-sional at the controllers could achieve a hal -way reasonable result. I an untrained useroperates the controllers catastrophic resultswere rather o ten the results. The use o amonitor measuring device can prevent that.Currently a good monitor measuring device

will cost rom 250,- plus and it really is amust or everybody, who deals pro ession-ally with images. Without such a measuringdevice, displaying images on a monitor islike fying blind.

So tproo

With the aid o a monitor pro le the user will always receive a cor-rect presentation o the image on the monitor (naturally only withinthe physical boundaries), regardless o the color space the image is in.Thus it can be available in di erent RGB working spaces, in a devicecolor space o even as CMYK in an printing process color space. In or-der or the pro le to be actually used by applications like Photoshop,it has to be set as system pro le or the monitor. This can be achievedon the Mac under "System pre erences/Displays/Color and on the PCunder "Control panel/Display/Settings/Advanced/Color Management.Most monitor measuring devices will set the pro le automatically as

Systempro le a ter calibration and pro ling. A little supervision whe-ther the newly created pro le really was set in the System settings is


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ok anyway.Since the monitor respectively the image editing application doesntcare about in which color space the image is in, it can additionallysimulate the output on a di erent device i there is a description o it

in the shape o an pro le available. This simulation can be chosen inphotoshop under the menu or Ansicht/Proo einrichten/Eigene (seealso chapter 1.7). In this case the images will get converted to thechosen simulation color space in the background and only then getdisplayed on the monitor. Thereby the displayed image will be limitedto the range, which can be produced by the output device.

This pictue showsthe original RGB

fle on the le t and the so tproo

presentation or the o set output

process on theright hand side


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In the range o digital photography or consumers we can not auto-matically assume the user to be amiliar with things like color manage-

ment. Thus all devices in that range are set in the way or all recordedimages to be displayed airly neat on an average monitor. Likewisethe printer drivers o all common inkjet printers are tuned in the wayall images printed will look hal way like the image was seen on themonitor. Since the sRGB working space comes very close to an averagemonitor there are usually very little problems in consumer workfowsbut not necessarily the best results possible.The eld o pro essional photography applies di erent working spac-es (see chapter 1.3) and there is a demand or a higher precision. Theimage displayed on the monitor is supposed to match the printout asclose as possible. This can only be achieved within the physical bound-aries o the according output device / printer. But the wishes can cometrue within these boundaries.

Pro ling

It is essential to have a pro le or the according output device, whichis characteristic or the device-material-combination used (printer, pa-per, inks, driver). In the ore ront it is important to calibrate the outputdevice. It is supposed to deliver optimum results and constant outputover the time. This is not working or some Color copiers since the out-put result is dependant on air temperature and humidity. But modernink jet printers deliver a constant result, as long as the air humiditydoes not exceed 70%. For the creation o a printer pro le a color chartwill get printed depending on the according driver so tware whichwill be measured subsequently with a spectralphotometer. I you area raid o the investment or such a device you will nd a pro essionalservice provider in every big city, who will create the pro les or you.Possibly Google can be o help nding one --> search or: ICC remote"pro ling service" to get a list. Just send the printed charts to one o

the service providers and you will receive the created pro le back. Thisneeds to be copied into the pro le directory o the according operat-ing system in order or applications like Photoshop to recognize thepro le. TIP: under Windows XP just right-click the pro le and choose"Install pro le".

Preview o the print

Since most printers are limited in color reproduction due to paper andink combinations used, it is good to display the nal result o the printin advance. Photoshop can realize this with the help o the pro le.The exact procedure will be described in the next chapter.

1.6 Visualisation in print


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Print with Preview

In order to print correctly the printer pro le needs to be chosen in the"Print with Preview" menu. Thus will convert the image be ore send-ing it to the printer driver in the way that it can be printed correctly.This printing alternative is called "Full Gamut Print" since it takes ulladvantage o the printers color space. At this point a so called Proocan be activated as well in order to simulate di erent output process-es on the according printer like e.g. o set printing or that purpose.To exercise control over whether the simulation o the printing pro-cess was success ul, there is the Mediastandard print or o set print-ing which is based on the mediawedge published by the FOGRA andUGRA. It is about color patches that will be printed and measured witha spectrophotometer. Each and every one o the color patches respec-

tively certain groups o them have to comply with certain tolerances,so that the print can be regarded as compliant to the o set print.A similar process or the control over RGB image data is under stan-dardization by the DIN.

Print with Preview Dialogue above. An output profle can be choosen. Below the Mediawedge (more in ormation rom www. ogra.org)


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Printing with a RIP

From applications like Photoshop images can be printed trouble- reewith simple pro les. A RIP (Raster Image Processor) is essenttial i a

layout with graphics, images and text is printed rom applications likeQuark Xpress or inDesign. Such a RIP can be avoided by creating a PDFle and printing it directly rom applications like Adobe Acrobat.

In the pro essional area this workaround can be too time-consumingmost o the times and the image setters or the printig lms and pla-tes still require the RIPs. They do have a couple more advantages. Forexample regular printjobs can be collected and printed space-savingor big posters can be split into a lot o smaller prints.When planning to purchase such a RIP pay good attention whetherit supports ICC color management. The pro ling o such a RIP is a bit

more complicated since they can adress the printer colors directly. Thiswill initially require e.g. the limitation or color-application and a line-arisation. I you are planning to build a pro le or your printer-paper-RIP combination you might want to consider to consult an expert.


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Postcard:100 x 150 mm

US-executive: 184 x 267 mmDIN A4: 210 x 297 mm

US-letter: 216 x 280 mmUS-legal: 216 x 356 mm

SUPER A4: 241 x 340 mmUS-tabloid: 280 x 432 mm

DIN A3: 297 x 420 mm A3 F: 305 x 457 mmSRA 3: 320 x 450 mm

SUPER A3: 328 x 453 mmDIN A3+: 330 x 483 mm

A3++: 329 x 558 mmDIN A2: 420 x 594 mm

DIN A2+: 480 x 628 mmDIN A1: 594 x 841 mm

DIN A1+: 625 x 914 mmDIN A0: 841 x 1189 mm

DIN A0++: 914 x 1250 mm

Tecco Format Guide

www.tecco.de


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At rst we nd that color settings in DTP applications via pro-gram settings are being discussed quite controversial in some ar-

eas and even among experts. Certain "Sets" have yet been prov-en in practice in such ways to reduce the probability o "coloraccidents" - thus can not totally prevent these. Furthermore in thesettings only such pro les are being used, which allow or stan-dardised production processes, and this should not be under-estimated are available ree o cost to the user (www.eci.org).Image editing can not be imagined today without Adobe Photoshopand thus shall be used or the choice o settings as an example. Thesecan be trans erred to other applications supporting color management.With the completion o this guideline Adobe Photoshop is avail-able in version "CS" or "8.01" or Windows (2000,XP) and MacOSX(10.3) as a component o the "Creative Suite". Adobe has attachedgreat importance to the compatibility o both plat orms duringthe development. This was accomplished quite well both on the

rst view (user inter aces, menus, palettes) as well as "under thehood". Particularly the handling o colors and the important as-sociated pro les will lead to roughly the same results on Appleas well as on windows-based systems. Di erences can be oundmainly or the locations o settings we will cater to this later.The screen captures used in the explanation were taken under OSX .The illustration doesnt di er undamentally rom windows systems.

Color settings

The color settings occupy a central importance or the presenta-tion and internal conversion o colors, and will be opened via themenu item "Photoshop"-> "Color settings". It is important to acti-vate the expert mode rst. The dialogue is divided into ve di er-ent zones: settings or the working spaces, association o the pro-

les (color management guidelines), the conversion rules or the

CMM and eventually the extended settings and the descriptions.The ECI gives out the ollowing recommendations or a workingspace: As RGB working space eciRGB should be used. This workingspace is very well suited or the elaboration o image material andhas achieved great acceptance in central Europe on a broad basis.Furthermore eciRGB covers all colors that can be reproduced with allcurrent output / printing processes. Under special circumstances e.g.the exclusive use o digital SLR cameras as a source or images thisrecommendation can be diverged rom. ( see 1.3). Choosing a CMYKworking space depends on the subsequent assignment. The ISOcoatedproved itsel in most cases. This color space describes the standardised

1.7 Settings in Photoshop


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printing process according to ISO-process norm 12647-2 or coatedand noncoated papers in a sheet o set printing process. ISOcoatedis also recommended or the presentation o greyscales and spot col-ors. (Note: This can be achieved by selecting the ISOcoated.ICC pro-

le rom the popup-menu next to theaccording working space and choosing"load greyscale settings" or "load spotcolors"). I the optimization o data or aprinting process is neither necessary norwanted, than "Grey Gamma 2.2" needsto be chosen as greyscale working space.For the color management guidelines thesetting "keep embedded pro le" shouldbe maintained . "Pro le errors" and"missing pro les" de ne the interactionwith missing pro les or pro les that donot comply with the chosen workingspace pro le. At this point, there is therecommendation to select all options.This will trigger photoshop to open adialogue whenever an image does not

contain a pro le or a pro le does not comply with the chosen workingspace and also the user will get the opportunity to convert into the work-ing space or to assign an alternative pro le when opening the image.For the conversion options the setting "Adobe (ACE)" has proven itseldue to the uni orm handling on di erent plat orms as well as the "percep-tive" setting. Blackpointcompensation as well as Dithering can be acti-vated as well. In the extended settings no options are necessary to choose.Sure enough all these settings appear complicated enough, but theECI has come up with a solution to this problem and publishes in-stallation applications on their homepage, which o ers ready-to-runcolor settings. These can be activated via the topmost popup-menu"Settings" and already contain the ICC pro les or the working spaces

thus wont need to be installed separatly. In conclusion the standardinstallation presets (e.g. Standard settings or europe" should not bechosen.

Opening image data

When opening image data Photoshops be-haviour will vary a ter setting the accordingworking spaces. The ollwing scenarios mayoccur:1.) No pro les embedded: I the imagedata does not contain a pro le, Photo-


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shop will show the ollowing dialogue while opening: The user ob-tains the options to either open the image without a pro le (in thiscase the according working space willbe used in order to visualize the RGB- or

CMYK-values), assign a working spaceor assign an alternative pro le and op-tionally convert to the working space.2.) Pro le embedded that does not complywith the working spaces: The embeddedpro le does not comply with the accordingworking space (RGB or CMYK) in Photoshopwhile opening an image, Photoshop will show the adjacent dialogue.The user has the option to either keep the embedded pro le, to convertthe image data to the working space directly or to discard the pro le.3.) Embedded pro le matches with working space: I the the embeddedpro les in the image data match the working spaces (RGB or CMYK),Photoshop will accept these image data without urther notice, pro-vided that no RAW-data is involved ( see also Chpt. 4.1 and 5.1 Rawdata; the behaviour o Photoshop will be described urther down).

With this multitude o options, it is essential to nd the appropriatestrategy ur the urther processing o images. In principle the are op-tions, to assign a pro le (which means that the pixel values in theimage will NOT get changed but the the colors displayed will varygreatly) or to convert (into the working space, in this case the pixelvalues will be CONVERTED, thus CHANGED the display on the moni-tor probably changes marginally). A generally accepted declarationabout which strategyis better can not be made at this point. It seemsto make sense though, when opening an mage to merely ASSIGN apro le, which describes the image accordingly (keep embedded pro-

le). This assigned pro le can still be changed at a later time whenCONVERTING this is nopt possible anymore. This approach should bepre erred also since there is no visual eedback (preview o the chang-

es) possible on the monitor. On the other hand i a di erent pro lewill be assigned via the menu item "Image -> Mode -> assign pro le"the changes will become visible when activating "Preview".The samedoes apply to the conversion o image data via the menu item "Image-> mode -> covert to pro le".

Opening raw les (raw data)

0.The opening o raw les (see also Chapter 4.1 and 5.1) takes anexceptional position. The so called "Camera RAW plugin" comes "in-the-box" with Photoshop 8, which enables opening raw les directly.The ollowing strategy has proven the test o time:


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1.) determine white balance / de ne neutral greyWhile opening photoshop will use the white balance determined bythe camera. This can be noticed in the right menu area under the"view" tab throught the white

balance preset "As camera". Ithe white balance is not pleasingenough (neutral areas e.g. showan explicit color cast) a changecan be applied in the rst placethroug either a global modi -cationby selecting "Auto" (orthe type o light available whilecapturing). I this approach willnot provide satis ying results,changing the color temperatur(lower values --> image will turnbluish, higher values --> imagewill turn yellowish) and the tint (negative values --> image will trungreenish, positive values --> image will turn magenta) can obtain aremarkable optimisation.A urther option is to adjust to a neutralgrey area in the image itsel .This will be acieved by choosing the grey balancetools in the win-dow on the le t and selecting (click) the the area o the image to bematched. Therupon Photoshop the colortemperature settings andthe tint until this tint is de ned as neutral (Comment: I "AdobeRGB"is selected, neutrl grey areas o the image will always hold valueso the color components R=G=B. I the mouse pointer is within theimage the values will be shown on the right side unter the imagewindow).2.) De ne ExposureA ter adjusting the whitepoint respectively the de nition o neutralgrey it is recommende to de ne the exposure. The highlights in theimage will be infuenced with the Ruler "Exposure", the shadows in

the image with the shadows ruler. When holding down the "Alt"-keywhile dragging the ruler, Photoshop will highlight the parts in theimage that are assigned as white ("Exposure" ruler)and hich parts othe image are assigned as "black" (shadows ruler).Comment: These visible parts o the image shownin these demonstrations will hold no picture detailswhatsoever, there ore they are "fat" or "clipped".3.) Adjust brightness, contrast and saturation

Choose the whitepoint either rom an entry in the list, by

moving the slider or via clicking the pipette within theimage.


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The rulers or "brightness", "contrast" and "satuation" will accom-plish a urther adjustment o the image itsel . The unctionality othese rulers is rather amiliar in the led o color corrections anddoes not require urther explanation.

4.) Apply sharpeningSharpness can beapllied to the images optionally even while import-ing the images . The sharpness settings can be ound in the rightmenu area underneath the "details" tab. Please note in order to

judgesharpness appropriatly a 100% zoom isessential. There ore itis rcommended to change the zoom to100% be ore changing thesharpening parameters.5.) Set parameters or the conversionBe ore actually converting the image a ew parameters need to bede ned. "AdobeRGB" can be recommended as color space at leastas long as Adobe Photoshop does not o er atlernatives or Workingspaces like ECI-RGB" or "PhotogamutRGB" in the Raw-plugin.I the image is already according the the users anticipation by nowand no urther optimisation o tonal range and colors is necessary inPhotoshop, it can be openend with 8.bit depth. In all other cases theimage should be opened with 16-bit color depth.The menu item "Size" o ers depending on the typeo camera used di erent options to either enlarge or reduce the image size. Thequality achieved is clearly superior to the regular scaling o images inPhotoshop. Now i its clear while importing the data to use it or alarge- ormat-poster, then the scaling should be apllied in the RAW-plugin.300 pixel per inch have proven to be appropriate resolution since it isvery close to the theoretical resolution limit o the human eye. Oncethe settings have been aproved with "ok" Photoshop will calculatethe nal image rom the camera data. This can take a couple oseconds according to the amount o data and theper ormance o thePC or Mac.

Visualisation

Photoshop CS makes a couple o technically matured tools availableor the visualisation o images.

An appropriatly calibrated and pro led monitor is a requirement inany case, which can display a color space a big as possible (see alo inchapter 1.5 Visualisation the monitor).When visualizing colors we need to consider the act, that the moni-tors and displays used today are NOT able to display all colors o anRGB- le (e.g. in ECI-RGB or even in sRGB) correctly. This is also true orthe printing colors used in an o set printing process even thoughthe o set printing color space according to ISO 12647-2 or uncoated


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paper is signi cantly smaller than the RGB color spaces mentionedabove, a highend monitor is necessary in order to display all colorsavailable in print on the monitor.I a visualisation o animage in a certain colo space is conducted, only

those colors will be shown which the monitor is able to display.But we have to nd in relativation that the majority o image ma-terial used will not exploit the color space o neither print nor RGBcolor space. Thus in most cases the visualisation o colors on themonitor will give us a pretty good impression o te nal results.I animage is availble in a RGB color space, the colors will be dis-

played virtually as accurate as possiblerom Photoshop and the color engine

o Photoshop. It is help ul in most casesto receive and evaluate a preview o theexpected results in print on the monitor.One will re er to this kind o preview onthe monitor as a "So tproo ".

Within the menu"Preview" choose the menu item "So tproo --> Cus-tom...". In the ollowing dialogue choose the pro le, which describesthe subsequent printing process.Tip: Most o the times it does make sense to choose the CMYK workingspace selected rom the Colorsettings at this point. This one resides atthe very top in the shortlist. "Relativ colorimetric" will be chosen asstandard rendering intent. For images with highly saturated colors it isrecommended to choose "Perceptive" in order to obtain the details inthese colors. The boxes or Blackpointcompensation and paper simula-tion should be activated.Attention: In case the images shal be printed in O set- or rotogra-vure it is urgently advisable to apply the standard pro les rom theECI-Homepage. The preinstalled pro les in photoshop with names like"Euroscale" and so on should not be used.A ter approving the settings the preview can be toggled on and owith a key shortcut (Mac: command-Y; Windows: Strg-Y)

In doing so the titlebar o the image window will show which colormode the image is presented in(Attention: Only the color mode willbe displayed), how the data is coded and which color space is simu-lated.Next to the visualisation it is also help ul to be able to recognize thecolor space o the actual image at all times. For this Photoshop o -

ers the possibility to display the chosen pro le or each particularimage in the in ormation section / status bar. There ore it is necessaryto switch to "Document pro le" in the in ormation section (by click-ing the tiny arrow on the right hand side o the section). The newlydesigne histogram palette is an additional essential tool o Photoshop


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CS. This will not onlysow the histogram o thele, but additionally the colored histograms

o each individual color channel. The palettecan be accessed via the menu item "Window

--> Histogram". In the histogram setting (tinyarrow in the upper right hand corner) thedisplay o a statistic can be shown as well asactivating the display o the single channels.


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Separation o images

For certain jobs it can be necessary to completly the data or print. Inthis case it is the photographers assignement to convert the RGB datain ready or press color separations ("CMYK data"). (Attention: Thiskind o conversion should only be per ormed on special request romthe clients side. In case the images are supposed to get edited at somelater time, an RGB (ECI-RGB, ...)color space makes a lot more sense asa trans er color space !!)Formerly these separations were created with so called "Separationt-

ables". This technique has been replaced by the use o ICC-pro les. Itmust be pointed out that the quality o the separation (and therebythe subsequent usability on the press) is primarily dependent on theapllied pro les. For this reason

it is explicitly re ered to thestandard pro les rom the ECIhomepage at this point.These pro les will achieve atop-quality result under allsorts o printing conditions andpaper types. It is disadvised toapply the pro les Euroscale""Swop" "Japan" installed byPhotoshop. The separationo the data can be initiatedvia the menu item "Image -->Mode --> convert to pro le".In the dialogue the designat-ed color space will be chosenand the rendering intent ap-pointed (when applying the"relative colorimetric" pleasenote that a great deal o de-tails will be lost in highly satu-rated colors). By activating the"Preview" box the result canbe visulised be ore actuallyprocessing the data. Once theseparation occured the imagedata is available in CMYK colormode.


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In principal the ollowing applies to all digital cameras: as in analoguephotography the illumination is dependent on these three actors likephotosensitivity in this case in regards to the sensor the exposuretime and the preset camera aperture.

ISO-sensitivities

With analogue cameras the photographer determines the sensitivitythrough the choice o lm material. With digital this isdi erent bynature, since the recording medium is a CCD- orCMOS-sensor , that isbuilt into the camera.There ore the sensitivity is always dependent on the image sensor andis indicated by ISO-steps just like with analogue lm material. In oppo-site to lm it can be changed which means that the photographercan choose certain ISO settings and switch the camera rom ISO 100 toISO 800 or signi cantly higher settings.These changed settings should be subject to caution though, since thephysical basic sensitivity o the CCD- or CMOS-sensor will stay the same:The higher values can be achieved via an electronic ampli cation othe image signal . Subsequently this also implies the basic backgroundnoise to get ampli ed as well. Many simple consumer cameras withhigh ISO settings will not produce images acceptable or the pro essio-nal beyond ISO 400. Premium digital SLR camera systems and o coursethe pro essional digital backs will still produce very good image mate-rial in many cases even beyond ISO 1.600 or even ISO 3.200. With theseimages ull o atmosphere can be produced even without the use ospeci c arti cial light though ideally suited or event photographyindoors or even shooting at night.

Studio- and f ashlights

When it comes to lighting or digital cameras there isnot even signi cant rethinking required. Pro essionalSLRs or and even digital backs will cooperate brilliant-ly with common Studio f ashlights or a system fash-light. Only high resolution scanning backs will partlyrequire a ficker- ree steady light system (like HMI),could mean trouble or a photographer.Please keep in mind that current available digital ca-meras o er a signi cantlysmaller dynamic range thanthe rather well-tempered negative lm material romanalogue photography. There ore extreme di erences

2 Photography

2.1 Exposure and lighting


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in contrast can create problems, thus either "loose" the dark details inthe shadows or clip the highlights and loose the details in this parts othe image. (see also "tip" on the next page).A digital SLR is usually equipped with a x-synchro contact or trigge-

ring a studio fash system. All studio fash systems can e triggered thatare equipped with this kind o contact. Naturally remote transmittersvia in rared or other ways to trigger a fash are possible.Generally one needs to pay attention to the white balance settingo the digital camera when shooting under arti cial light. Either thecamera will be manually adjusted in terms o color with a white pieceo paper or a greycard or a whitebalance preset or fashlight respec-tively daylight needs to be chosen. Naturally the use o a designatedmeasuring device or the creation o individual color pro les or thespeci c camera is recommended, in order to produce constant colorvalues. For the same reasons it is essential or a studio fash system todeliver a power / fash intensity as constant as possible as well as con-stant color temperature. Some studios will per orm complete measu-rings o the according fash systems, in order to utilize only those sys-tems or the subsequent set assembly, that all eature matching colortemperature.For a reportage assignment one is responsible or seeing thatthe digital SLR and the according system fash can communi-cate with each other: In many cases a regular TTL-measure-ment or the fash intensity is NOT possible but one has to

all back to the speci ed TTL-technology (D-TTL, E-TTL) othe camera respectively the matched upon system fash.That's why many manu acturers o er new product lines osystem fashlights or their digital SLRs, that are adapted tothese special characteristics.

Aperture settings o the camera

The Aperture setting o a digital camera is similar to a regu-lar analogue camera. In relation to the used lens maximum

and minimum aperture settings are allowed, re erring to the size othe opening in the lens that determines the amount o light allingonto the CCD-sensor and in cooperation with the exposure time a -

ects the correct exposure o the image. With simple consumer came-ras the aperture is o ten set via cursor keys in the settings menu on theLCD-monitor, with a digital SLR the aperture setting can be achievedde nitely more com ortably by means o a rotating knob or directly atthe aperture ring on the lens.As a result o emerging defection e ects with extremely small aper-ture settings digital photographers are recommending 16 as mini-mum aperture setting, even better with only 11.


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Exposure - problems

Even with the seducing high image resolutions, which are so-metimes even higher than those o SLR cameras many o themare not appropriate or pro essional use because the exposureclearance is too small or various reasons.It starts with the lowest possible ISO-sensitivity or the camera,which is simply too high or most tasks. Almost all models arestarting wit an ISO-value o 100 and some even at ISO 160: Incase o a studio-shooting this can mean that the fash systemcan not regulated low enough and there ore one has to workwith simply too much light. This can be extremely atal or ex-ample with portrait photography or which a larger apertureopening in order to outline rom an out-o - ocus background.

But in this case only a too small aperture settings and there ore toomuch depth-o - eld will be applied with a consumer camera. The mi-nimum aperture setting with many consumer camera is only 8, be-cause o the small measures o the mini-lens as well as the recordingsensor and subsequently the according overall geometry inside thecamera aperture settings beyond 8 would result in defection e -

ects (see also "Aperture settings")Outdoor shootings with sunshine are there ore only possible with ex-tremely short exposure settings and wont allow any motion e ects bydragging the camera in motion while taking the picture.A neutral density lter is pretty much the only thing that will help totease out a couple o -stops.

Tip: Underexposure is better than overexposure

High dynamic ranges images thus extreme contrast between lightand dark it is recommended set the exposure on the highlights andto put up with an underexposure in the dark areas in an image. Sincethe dark areas in an image can be retrieved by a contrast- or tonalrange optimization even though this is not visible on the monitor

at rst the in ormation in the highlights can not be saved rom thecompletely white elements o an image in case o an overexposure inthe highlights.In order to optimize the exposure the pro essionals will use the rawdata ormat most o the times, in order to develop the images "digi-tally" systematically. Additionally the conversion o raw images to 16-bit data is a big advantage in terms o postproduction, because a lotmore tonal gradation is available or editing the image in Photoshopa ter the conversion into such a 16-bit ti le. There the dark portionscan be brightened selectively in order to receive a more balanced nal

result.


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Digital cameras save its images in the shape o digitally coded thusconverted to numerically values- les. The ormal design o these les

can be very di erent. A couple o standard ormats have accomplishedthemselves which all have their advantages and disadvantages andthere or coexist in digital photography.

Color depth

A le o an image usually exists rom the three basic undamentalcolors red green and blue. We describe the color depth as the bit-quantity, with which these shades or each one o these colors can bedisplayed. In 8-bit we can digitally save 2 to the power o 8, thus 256di erent numerical values. For each individual pixel a brightness valuebetween 0 and 255 will be saved or each o the three RGB color chan-nels. Every pixel can consist o 256 green, 256 red and 256 blue tonalvalues thus rom totalling 256 x 256 x 256 = 16,8 million colors.Increasing the color depth will result in the ability to reproduce evenmore shades. Many digital cameras or this reason work internallywith a signi cantly higher color depth, than will be saved at the endo the capturing- and editing process in the 8-bit image le. 12-bit arequite common or example which process 4.096 tonal value shades percolor excerpt, respectively even 14 bit, with which even 16.384 shadescan be achieved per color excerpt.Even though the human eye is by ar not capable to di erentiate the16,8 million colors o an 8-bit display, the higher color depth is im-portant. The reason or this is the di erent brightness reception ohumans and digital cameras. The camera is able to di erentiate verywell in the bright areas and the eye in the dark ones. With the largeramount o shades and the human reception a better photo dynamiccan be achieved with the optimized gradation o brightness. The high-er color depth is also used in image editing or additional contrast-and tonal value optimization.

Compression

One o the biggest problems in digital photography consists i hav-ing to save the immense amount o data on a storage medium. A 6-mega-pixel image consists o altogether 6.291.456 pixel. For each pixelthe camera has to save the color in ormation or red, green and blue.Each color in ormation consists o 3 x 8 bit (256 shades) per color (seecolor depth), thus the image consists o 6.291.456 x 24-bit, which are150.994.944 bit respectively 18.874.368 Byte (approx. 19 megabyte).Storage media or digital cameras are not cheap though. For this rea-son one was looking or possibilities to minimize the data. The solu-

2.2 Formats, Color depth and compression


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tion was ound in the "compression" o the les, thus in mathemati-cal procedures to save the data more space-saving. As a undamentalprinciple we need to di erentiate between two techniques:losless compression (e.g. Ti -LZW)

lossy compression (e.g. JPEG)A lossless compression is characterized as a procedure in which theoriginal le in spite o compression o the image can be reproduced1:1. A simple lossless compression consists o saving redundancies (re-peating in ormation) in a concentrated orm rather than singular.The Ti -LZW ormat applies this procedure but achieves only very lowcompression ratios, since the pixels o a photo practically all hold verydi erent color values.For this reason the Joint Photographic Experts Group proposed a newcompression technology and while at it even named it a ter itsel :JPEG. It takes advantage o the weakness o the human eye to di er-entiate color di erences less exact than brightness di erences. JPEGreduces by a mathematical procedure "discreet cosinus trans orma-tion DCT" the color in ormation o the image by summarizing the col-or in ormation o multiple pixels to one in ormation, the brightnessvalues will stay untouched. Due to the loss o some o the originalin ormation the images will not be reproduced into the exact originalcondition thus will be saved lossy. This loss is accepted becausea) the loss o quality with a cautious JPEG compression are not visibleand will stay tolerable even with a stronger compression.b) the space saving o JPEG is immense: The initially mentioned 19-megabyte le o a typical photo will be reduced to just under 3-mega-byte even with a weak JPEG-compression.

JPEG- ormat

JPEG has established itsel as a standard with digital cameras. Whileeaturing a strong compression power it o ers urther bene ts:

the actual intensity o compression is scale able. The more intense the smaller the les will get yet the quality loss will increase. Digi-

tal cameras o er the chance to between di erent JPEG grades. Thephotographer gets to decide whether he pre ers a smaller le size orbetter quality.JPEG can be opened, edited and saved by practically every single im-age editing application available. But it is not only or image editingapplications but also or the internet one o the most essential or-mats or photos.Graphic- and layout applications increasingly utilize JPEG-imagesMany cameras will save the images directly as JPEG , which can beessential due to the amount o storage necessary as well as the pro-cessing speed. In postprocessing the photos shall be saved into the


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JPEG ormat at the end o the processing due to the lossy compressionwhile saving.

TIFF

Ti - les are normally saved without compression. Every pixel containsthe complete in ormation, provided by the camera.This usually leads to large image les. Ti also supports 16-bits colordepth. This is an advantage since a lot more shades are available oreach color nuances. Practically every layout- or graphics application iscompatible with Ti .

RAW- ormat

The raw ormats take an exceptional position among the image le

ormats. The in ormation coming rom the recording sensor will besaved without urther compression or interpretation. As an outcomethe camera will not actually save a digital image in the truest sense oit, but saves "raw data" on the memory card. A normal image edit-ing application can not read this in ormation because o saving theraw les and the according raw ormats depends on the accordingcamera manu acturer. Thus the raw data can be manually edited toevery detail with the appropriate application, even the optimizationo whitepoint as well as the subsequent sharpening o the photo ispossible appropriate image editing application / an RAW-converter.

Since the possibilities o editing are so immense, the raw ormats be-long to the most popular le ormats in the elds o pro essional pho-tography. Instead o leaving so tware sharpening, tonal correction viaGamma-coontrol, behavior o colors as well as other parameters tothe interpretation o the camera, the photographer can convert ac-cording to his own gusto with the accompanied or third-party conver-sion tools. Adobe Photoshop o ers since version 8.0/CS the possibilityto read many o the manu acturers own raw-variations. To open sucha raw- le kind o resembles the development o an analogue lm ina classic photo lab, with the opportunity to take infuence on the out-come o the photos to a large extent.. For this reason more and moreconsumer digital cameras eature the digital raw ormat.By this the color depth o the recording system can be obtained andwill not get reduced to 8-bit. This guarantees a or higher dynamicrange in the photos.The main disadvantages o raw les lies within the slightly more com-plicated and thus time-consuming handling because the photos haveto be processed compellingly, in order to get displayed and used ur-ther on the computer.


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DNG

Adobe is ond to replace the speci c manu acturers raw data ormatswith a consistent "digital negative" and put a proposal on the tableduring Photokina. This kind o development is eligible rom the usersperspective, whether the manu acturers will jump on it needs to beawaited. The DNG is an enhancement o the in ISO 12234-2 standard-ized Ti -EP (electronic picture).

JPEG2000

An interesting, but rankly in digital photography so ar not a verywidespread ormat is JPEG2000. It does o er a lot o advantages likee.g. the losless compression and high quality with strong compression.Owners o Photoshop CS get the chance to read and write JPEG2000

les The optional plugin is actually application CD under goodies.Tip:

It is advisable whenever it needs to go ast and an individual postpro-duction is not possible, to choose JPEG with a low compression = highquality. But i it is possible in di cult situations to save in the raw data

ormat, then it should be applied. Additionally a subsequent controlo the histogram is recommended directly a ter the exposure (i thecamera makes this possible).Some o the modern digital SLRs are capable o saving raw data andJPEG- les simultaneously on the memory card.

Links

www.jpeg.org/


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The term resolution is o ten equated with the number o pixels (actu-ally re erred to a sample rate), that a camera delivers. This equation is

only applicable under ideal reproduction conditions, rom which realcameras are more or less ar-o . A bad lens in ront o the camerameans that even with an extremely high number o pixels not a goodan detail-rich photo can be captured. The quality o the reproductionis dependent on the camera and lens used and hence con not bet con-ducted any urther at this point. The ollowing observations will thusrelate to the idealized reproduction in the shape o pixels.

How big o an image le is necessary in order to get printed precisely?Every photographer should ask himsel this question, be ore sendinghis photos to the printer. Because only i there is su cient enoughdata available or all the details o the motive, they can get repro-duced per ectly. Especially with illustration books, magazine photosor urther large ormats one can accept no compromises at this point.

A care ul planning process already starts be ore the actual capture,since there is no way to add the data a terwards. For instance chang-ing the size a terwards- the so called interpolation will not increasethe resolution in terms o detail reproduction. Since this will create ad-ditional pixels purely through average determination the photo willcome across dull and out o ocus a ter the operation. For this reasonthe right setting needs to be chosen, even be ore the shutter releasebutton is pressed.

Resolution on screen and on paper

Just how the image ormat a ects the le size, is describe in the previous

chapter. However kilo- and megabytessay little about to which degree a pho-

to can be printed on paper in a highquality.This is particularly a ected by the print

ormat and method. The number opixels depends on the speci cations,

rom which the exposure needs to con-sist o marginally.These dots are additionally re erred to as pixels, an arti cial englishword rom picture and element. The pixel as a undamental elementis no constant dimension, but is very di erent depending on each out-put medium. Thus they can b

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