7
TECHNOLOGY FOCUS Practical Digital Photography for Surgeons William B. Schroder, MD Section of Vascular Surgery, UMKC School of Medicine, Truman Medical Center, Kansas City, Missouri As a surgeon, you know the value of an image. Every clinical journal is filled with diagnostic images, operative photographs, and pathology slides. Over the years, we have collected and badly maintained our collections of 35-mm Ektachromes, ex- pensive custom slides, and off-tone homegrown “pseudo- diazo” text slides. I kept an expensive, motor-driven camera body, heavy 100-mm macro lens, and ringlight in its own bag locked in my file drawer waiting for interesting pathology to crop up. I missed some good images because the setup was cumbersome to lug around. I became hooked on computers as tool and toy around 1988, and I observed bemusedly when the first expensive but weak digital cameras hit the market. The thousand-dollar, million- pixel barrier was a long time coming down, but when it did, I was there (mostly out of morbid curiosity). My first digital camera was a Kodak DC-120 (Rochester, New York). This oddly shaped camera was slow and power hungry yet offered 1-megapixel resolution and decent image quality. Although suitable for PowerPoint (Microsoft Corporation, Redmond, Washington), enlargements were grainy and I was not yet ready to abandon film. I ordered a Nikon Coolpix 950 (Nikon Corporation) shortly after its introduction, and had to wait weeks on backorder for it to arrive. With its 2-megapixel resolution and outstanding im- age quality, it quickly became my everyday camera. Its small size and superior macro capabilities allowed me to use it easily in the operating room, and I soon had a CD-ROM collection of hun- dreds of surgical images that made even impromptu “Grand Rounds” presentations a snap to assemble. At home, even 8 10 enlargements from the 950 were good, and the ability to manipulate the images in Photoshop (Adobe Systems Incorpo- rated, San Jose, California) and control the output made it superior to film for me. In 1999, I swallowed hard and traveled to Ireland with the 950 as my only still camera. Daily emails of JPEG files “back home” were well worth lugging my clunky laptop across the Atlantic (although international dialup service can be pricey). I ordered (and waited) for a Nikon Coolpix 5000 the day it was announced. This 5-megapixel camera is now my “family” camera, but the 950 stays at work and gets regular use. My colleagues and I own at least 10 Coolpix 9xx cameras (the 2-megapixel 950 and the similar 3-megapixel 990 and 995), and a growing number have purchased the 5000. Many of our professional journals accept digital images (often preferentially) in lieu of the traditional “5 7 glossies.” Even our hospital is going filmless: I can examine radiographs on my desktop PC only moments after they are done, and dictate vascular ultra- sounds from my 21-inch “viewbox.” The viewer software allows image capture without having to take a photograph from x-ray film. Is film-based photography dead? For surgeons and our prac- tices, it is. It is time to embrace the digital world and its tools. This article will cover the concept of digital images, image gen- eration, file formats, image manipulation, image storage and retrieval, and how I use digital photography in my surgical practice. DIGITAL IMAGES: THE PIXEL AND IMAGE SIZE The pixel (short for picture element or picture cell) is the equiv- alent of the silver “grains” from film-based photography. Un- derstanding and manipulating the individual pixel is funda- mental to working with digital images. Like tiles in mosaic artwork, images are built of pixels. This image of Abraham Lincoln (Fig. 1, courtesy of Jelly Belly Candy Company, Fair- field, California) is a jellybean mosaic. Progressive magnifica- tion of the image reveals the individual jellybeans and then the individual square pixels that comprise each bean. Remember the “Lite-Brite” Toy? We created images 1 colored peg at a time. Pixels are generated by a photosensitive chip. The charge- coupled device (CCD, Fig. 2) is the most common photosensor for digital cameras. The photosensors on the chip are arranged in arrays of rows and columns, and each sensor is covered with a microlens and filter to create a single pixel in 1 of the 3 “additive” colors (red, green or blue, “RGB”). New CCDs (not yet readily available) allow each pixel to record full-spectrum color. A discussion of CCD technology is beyond the scope of this paper, but digital photography magazines cover this topic well. Pixel densities (the number of photosensors per square centimeter) are growing with a similar curve as microprocessor Correspondence: Inquiries to William B. Schroder, MD, Section of Vascular Surgery, UMKC School of Medicine, Truman Medical Center, Surgery Administration, 2301 Holmes, Kansas City, MO 64108; fax: (816) 855-6084; e-mail: william.schroder @tmcmed.org CURRENT SURGERY • © 2002 by the Association of Program Directors in Surgery 0149-7944/02/$22.00 Published by Elsevier Science Inc. PII S0149-7944(02)00666-9 581

Practical digital photography for surgeons

Embed Size (px)

Citation preview

Page 1: Practical digital photography for surgeons

TECHNOLOGY FOCUS

Practical Digital Photography for Surgeons

William B. Schroder, MD

Section of Vascular Surgery, UMKC School of Medicine, Truman Medical Center, Kansas City, Missouri

As a surgeon, you know the value of an image. Every clinicaljournal is filled with diagnostic images, operative photographs,and pathology slides. Over the years, we have collected andbadly maintained our collections of 35-mm Ektachromes, ex-pensive custom slides, and off-tone homegrown “pseudo-diazo” text slides. I kept an expensive, motor-driven camerabody, heavy 100-mm macro lens, and ringlight in its own baglocked in my file drawer waiting for interesting pathology tocrop up. I missed some good images because the setup wascumbersome to lug around.

I became hooked on computers as tool and toy around 1988,and I observed bemusedly when the first expensive but weakdigital cameras hit the market. The thousand-dollar, million-pixel barrier was a long time coming down, but when it did, Iwas there (mostly out of morbid curiosity). My first digitalcamera was a Kodak DC-120 (Rochester, New York). Thisoddly shaped camera was slow and power hungry yet offered1-megapixel resolution and decent image quality. Althoughsuitable for PowerPoint (Microsoft Corporation, Redmond,Washington), enlargements were grainy and I was not yet readyto abandon film.

I ordered a Nikon Coolpix 950 (Nikon Corporation) shortlyafter its introduction, and had to wait weeks on backorder for itto arrive. With its 2-megapixel resolution and outstanding im-age quality, it quickly became my everyday camera. Its small sizeand superior macro capabilities allowed me to use it easily in theoperating room, and I soon had a CD-ROM collection of hun-dreds of surgical images that made even impromptu “GrandRounds” presentations a snap to assemble. At home, even 8 �10 enlargements from the 950 were good, and the ability tomanipulate the images in Photoshop (Adobe Systems Incorpo-rated, San Jose, California) and control the output made itsuperior to film for me. In 1999, I swallowed hard and traveledto Ireland with the 950 as my only still camera. Daily emails ofJPEG files “back home” were well worth lugging my clunkylaptop across the Atlantic (although international dialup servicecan be pricey).

I ordered (and waited) for a Nikon Coolpix 5000 the day itwas announced. This 5-megapixel camera is now my “family”

camera, but the 950 stays at work and gets regular use. Mycolleagues and I own at least 10 Coolpix 9xx cameras (the2-megapixel 950 and the similar 3-megapixel 990 and 995),and a growing number have purchased the 5000. Many of ourprofessional journals accept digital images (often preferentially)in lieu of the traditional “5 � 7 glossies.” Even our hospital isgoing filmless: I can examine radiographs on my desktop PConly moments after they are done, and dictate vascular ultra-sounds from my 21-inch “viewbox.” The viewer software allowsimage capture without having to take a photograph from x-rayfilm.

Is film-based photography dead? For surgeons and our prac-tices, it is. It is time to embrace the digital world and its tools.This article will cover the concept of digital images, image gen-eration, file formats, image manipulation, image storage andretrieval, and how I use digital photography in my surgicalpractice.

DIGITAL IMAGES: THE PIXEL ANDIMAGE SIZE

The pixel (short for picture element or picture cell) is the equiv-alent of the silver “grains” from film-based photography. Un-derstanding and manipulating the individual pixel is funda-mental to working with digital images. Like tiles in mosaicartwork, images are built of pixels. This image of AbrahamLincoln (Fig. 1, courtesy of Jelly Belly Candy Company, Fair-field, California) is a jellybean mosaic. Progressive magnifica-tion of the image reveals the individual jellybeans and then theindividual square pixels that comprise each bean. Rememberthe “Lite-Brite” Toy? We created images 1 colored peg at a time.

Pixels are generated by a photosensitive chip. The charge-coupled device (CCD, Fig. 2) is the most common photosensorfor digital cameras. The photosensors on the chip are arrangedin arrays of rows and columns, and each sensor is covered witha microlens and filter to create a single pixel in 1 of the 3“additive” colors (red, green or blue, “RGB”). New CCDs (notyet readily available) allow each pixel to record full-spectrumcolor. A discussion of CCD technology is beyond the scope ofthis paper, but digital photography magazines cover this topicwell. Pixel densities (the number of photosensors per squarecentimeter) are growing with a similar curve as microprocessor

Correspondence: Inquiries to William B. Schroder, MD, Section of Vascular Surgery,UMKC School of Medicine, Truman Medical Center, Surgery Administration, 2301Holmes, Kansas City, MO 64108; fax: (816) 855-6084; e-mail: [email protected]

CURRENT SURGERY • © 2002 by the Association of Program Directors in Surgery 0149-7944/02/$22.00Published by Elsevier Science Inc. PII S0149-7944(02)00666-9

581

Page 2: Practical digital photography for surgeons

transistor densities (Moore’s Law states that the number oftransistors on a chip will roughly double every 18 months).

The size of a digital image is expressed as the number of pixels(megapixels, MP, millions of pixels) or pixel dimensions (aspixel counts in length � width). Thus, an image that has 1800rows and 1200 columns has 2,160,000 pixels, or 2.16 MP. It isamazing how few pixels actually comprise a television image(approximately 160,000). Table 1 gives image size informationfrom some well-known sources. The 35-mm slide has been thebenchmark to measure digital image progress. Estimates vary,but the amount of useable data that can be obtained from a35-mm slide is just over 5 MP. The current crop of affordable(sub-$1000) consumer-level cameras is producing images in the

4 to 6 MP range. I believe the era of film-equivalence is here, formost of us. However, super fine-grain films like Ko-dachrome-25 (Kodak) can probably produce higher pixelcounts, and most studio work is done with medium-format orlarger. These 6 � 6 (cm) films have over 4 times the area of a35-mm negative. That would place the pixel count for medium-format film around 21 MP.

DIGITAL IMAGES: DATA SIZE AND FILE SIZE

To store a pixel electronically, the computer file needs to storemore both the location and the color of each pixel. Bits, bytes,and the like are beyond this discussion, but a pixel can be pure

FIGURE 1. Progressive magnification of this jelly bean mosaic demonstrates the “pixel” nature of a mosaic, and then the pixel nature of the individualbeans. ([r]Reg. TMs of Jelly Belly Candy Company. Used with permission from the Jelly Belly Candy Company.)

FIGURE 2. The charge-coupled device and its accompanying circuits create the pixels for an image.

582 CURRENT SURGERY • Volume 59/Number 6 • November/December 2002

Page 3: Practical digital photography for surgeons

monochrome (either a black dot or a white dot), grayscale, orvarying degrees of color. Although a bit simplified, each pixelcan be stored as 1 byte if it is monochrome, grayscale or up to256 colors, 2 bytes if up to 65,000 colors, or 3 bytes if it uses“true-color” (16 million colors). Therefore, the data size of animage is equal to the length � width � color depth. For exam-ple, a 2.16-megapixel image (1800 � 1200 pixels), in true-color(3 bytes per pixel), would have a data size of 6,480,000 bytes(6.3 megabytes, MB, remembering that a megabyte is 1024bytes).

The image data are captured and stored in a digital file in oneof several file formats. The most important concept of file for-mats is compression. Mathematic algorithms are applied to theimage data to store it as a file. Some algorithms can compress(shrink) the image data into a smaller and more easily storedand transferred file. Extreme compression is possible if some“less important” image data are discarded. This type of com-pression is called “lossy.” Lossy compression algorithms offervariable compression percentages based on the degree of com-pression desired (and the amount of image data irretrievablydiscarded). Table 2 shows some common file formats and thefile size that is produced when the image data is stored. Manymore file formats are available (try a web search on “file format

information”). For practical reasons, use a file format that meets3 needs: your software supports it, those you share files with canopen and view it, and it suits your storage, archiving, and re-trieval capabilities. Professionals tend to work with TIF files,because the format is well supported and no image data are lostwith multiple manipulations and file-saves. If the same JPG fileis repeatedly “tweaked” and resaved, there can be progressivedata loss. This does not happen if you just view the file, just ifyou keep hitting the “save” button. I work most of the time withhigh-quality JPG files, and do a few things to combat potentialdata loss. I take all my images using my camera’s “fine” setting(most cameras let you choose that your images be saved uncom-pressed (as TIF files, for instance, or with 1 or more levels ofJPG compression). The fine JPG setting provides an excellentbalance between storage on the memory card and quality. I thenburn these images onto a CD-ROM before doing any manip-ulations. I burn at least 2 copies of important images, and keep1 copy at work and 1 copy at home. I am then free to manipu-late, crop, recolor, and so on these images without fear of losingthe original data. I save these “improved” files only once andthen burn these corrected files onto another CD-ROM. I thenhave CDs labeled “Raw” and “Tuned”.

GENERATING IMAGES: CHOOSINGA CAMERA

There are many fine digital cameras, but for the practicingsurgeon, the most important camera characteristics are porta-bility, macro capability, copy-stand use, and the ability to copy(digitize) an existing slide collection. I will focus on the NikonCoolpix 9xx series (950, 990, and 995) because they fulfill theseideal characteristics so well. I think these are the best “Medical”cameras available. (I have no financial conflict-of-interest re-garding Nikon.) I own a 950, but it has been supplanted by the990 and 995. I will focus on the 995 (Fig. 3), which (like the950) creates a 3.15 MP image (2048 � 1538) of excellent color,sharpness, and dynamic range. Multiple automatic modes plusfull manual controls are available. On-camera flash is modest

TABLE 1. Image Size � Rows � Columns, Expressed in Millionsof Pixels, Megapixels, MP

Source ImageMillions of

Pixels

Television 320 � 525 0.16 MPHTDV (analog, USA) 600 � 625 0.375 MPFirst Hubble Camera 800 � 600 0.48 MPComputer Screen 1024 � 768 0.79 MPKodak DC-120 1280 � 960 1.23 MPNikon Coolpix 950 1800 � 1200 2.16 MPNikon Coolpix 995 2048 � 1536 3.15 MPNikon Coolpix 5000 2560 � 1920 4.92 MP35-mm Color Slide 2760 � 1890 5.22 MP (est.)New Hubble Camera 4096 � 4096 16.8 MP (2 ccd’s)Human Eye 11k � 11k 120 MP

TABLE 2. File Size Produced When Image Data Are Stored. The Original Image Was 2560 � 1704 Pixels With 16 Million Colors*

File Name Extension Compression Data Loss File Size

Windows Bitmap BMP None None 12.8 MBTagged Image File TIF, TIFF None None 12.8 MBTagged Image File TIF, TIFF Modest (LZW)

Lempel-Ziv-WelchNone 8.9 MB

Portable Network Graphics PNG, PING Modest None 8.4 MBMacintosh Picture PICT Modest None 8.2 MBGraphics Interchange Format GIF Yes Possibly** 2.9 MBJoint Photographic Experts Group JPG, JPEG Yes, Modest Yes, not usually noticeable 1.2 MBJoint Photographic Experts Group JPG, JPEG Yes, Moderate Yes, sometimes noticeable 576 KBJoint Photographic Experts Group JPG, JPEG Yes, Marked Yes, often noticeable 357 KB* Original photograph taken by a Nikon Coolpix 5000 saved by the camera in its “Fine” JPG mode. File conversion and saving done by Adobe PhotoshopElements (©2001, Adobe Systems Incorporated)

** The Graphics Interchange Format (GIF) while technically “lossless,” is limited to only 256 colors. Therefore, if you save a true-color photograph inGIF format you are discarding color data.

CURRENT SURGERY • Volume 59/Number 6 • November/December 2002 583

Page 4: Practical digital photography for surgeons

but very serviceable for operating room photography, and ex-ternal flashes can be connected. Magazines rate the imageshighly, although not always the best. The “twist-body” con-struction allows the camera to fold flat and fit easily in a labcoatpocket, yet still allow enough lens-travel to give good (4� op-tical) zoom range, and “best of breed” macro capability withoutthe “front-to-back” bulk that makes other cameras difficult topocket. The lens can focus to approximately 2 cm (0.8 inches)from the lens! This closeup capability produces outstandingoperative photographs and allows an inexpensive (approx $70street) screw-on attachment that copies slides and negativeswith ease (more below). The tripod socket on the bottom allowseasy copy-stand use.

GENERATING IMAGES: LIVE, SLIDE COPY,COPY STAND

Use of a camera in the operating room requires ease-of-use, sothat you or an assistant can take photographs quickly with aminimum of disruption to the flow of the surgery. Using anextra pair of sterile gloves, surgeons can hold the camera awayfrom their bodies and twist the lens down to the field whilecomposing the image in the LCD (Fig. 4). Alternatively, assis-tants can photograph over the surgeons’ shoulders while hold-ing the camera at arms length, see the field through the LCD,and take some shots without any disruption to the procedure.

The slide copier attachment (Fig. 5) means you do not haveto purchase an expensive, fussy, slow (30 seconds or more perslide) device to do what the slide copier does in a few seconds.Remember that the typical 35-mm slide contains about 5.2 MPof data, so slide copies with the Coolpix 995 (3.15 MP) areclose. Use the Coolpix 5000 (4.9 MP), and you lose nothing bycopying and tossing your slide collection. (Do not forget thatthe average projected PowerPoint image needs less than 0.8MP, see below.) I set the camera on macro, indicate the lightsource as fluorescent, place a slide in the holder, hold theadapter up to an x-ray view box, and push the shutter release. I

can copy about 6 slides per minute with this technique. Certainpoorly exposed slides may do best with some on-camera expo-sure compensation (the Coolpix 5000 can do auto-bracketing.)

Digitizing computed tomography scans, plain films, and an-giograms is essential for making talks and discussing cases on-line, and a copy stand is the best way to go about making them.Although Fig. 6 shows a high-end, pricey copy stand, an oldx-ray view box and a $75 copy stand (see http://www.adorama.com) will produce the same images. While on the subject ofcopy-stand use, I find that photographing textbook images(minding all necessary fair-use statutes) produces better resultsthan does flatbed scanning. Moire patterns are a problem whenscanning halftone images. Halftoning is a technique for pro-ducing continuous-tone-appearing images with only solid inkcolors, and it is used in most publications. Optical interferencecreates bands of light and dark (the Moire) on the output file.Software manipulation and filters can minimize this problem,but I find that a digital camera is less subject to this problemthan is a scanner, and it usually prevents the problem in the firstplace.

FIGURE 3. The Nikon Coolpix 995. FIGURE 4. Use of a digital camera in the operating room: The twist-action of the 9xx series (950 shown) cameras allows holding the camerawell away from the face while still composing good images. The macromode produces superior closeups.

FIGURE 5. The Nikon Slide Adapter is shown here attached to aCoolpix 950 camera. It also attaches to the 990 and 995. With anadapter, it will attach to the Coolpix 5000.

584 CURRENT SURGERY • Volume 59/Number 6 • November/December 2002

Page 5: Practical digital photography for surgeons

IMAGE MANIPULATION: THEDIGITAL DARKROOM

Once you have your raw image file safely tucked-away on CD-ROM, its time to “tune” the image to your needs. Image-ma-nipulation software abounds: As far as I can tell, every cameraships with one or more software packages: some “lite” or limitedversions, some “full” but outdated versions (upgrade available atadded cost), and some full-fledged, current packages. There areshrink-wrapped, shareware, freeware, and demo versionsaplenty. Some are part of suites that let you burn data, video,image, and music CDs. There is even image manipulation builtinto most Windows versions (Microsoft Photo Editor in Win-

dows XP). In general, almost any package will let you do thebasic functions: Crop, zoom, rotate, and adjust contrast andbrightness (gamma). Some packages can automate this for youwith “picture-fix” and “red-eye” macros and wizards. Thegranddaddy of all image packages seems to be Adobe Photoshop(about $590 street). If Photoshop (with or without one of its3rd-party add-ins, called “filters”) cannot do it, it probablycannot be done. For the lighter of wallet, Adobe PhotoshopElements (under $70 street) has almost everything the parentprogram contains and some wizards and other “ease of use”features that it does not (Fig. 7). For first-time users, the learn-ing curve for Photoshop products may be a bit daunting, but itis worth the climb. My suggestion is to either use what comesfree with your camera or just order Photoshop Elements.

IMAGE OUTPUT: SCREEN, EMAIL,POWERPOINT, PRINTER,PHOTOFINISHERS, JOURNALS

Because an image is meant to be used, how you manipulate andsave the image should be geared toward how you plan to offer itsoutput. Because you already have the original image tuckedaway on a CD-ROM (don’t you?), you can tailor your image tothe output you plan to use. Many people display their images on

FIGURE 6. Use of a copy stand to digitize x-rays.

FIGURE 7. Adobe Photoshop Elements has almost all of the features anyone needs for image-editing.

CURRENT SURGERY • Volume 59/Number 6 • November/December 2002 585

Page 6: Practical digital photography for surgeons

their computer screen, and many users still have screen resolu-tions of 800 � 600 or 1024 � 768. Most computer projectorsare likewise limited to 1024 � 768 pixel resolution. “Powerusers” with 19- and 21-inch monitors may use screen resolu-tions of 1280 � 960. Still, that “high-end” screen resolutionuses only 1.2 megapixels, and the newer cameras are taking 4 to6 megapixel images! Using a higher resolution image on mon-itors and projectors will result in 1 of 2 things: The monitor willdisplay only part of the image, and the user will have to “pan”the image to see its entirety, or the software will “shrink-to-fit”the image so it can all be seen. The former is fine if you are“tweaking” the image but is a pain if you are trying to view it.The latter results in larger files to move around and slowerdisplay times, whereas the software crunches the pixels.

A special note on PowerPoint presentations: You are proba-bly best to assume that your presentation will run on a 1024 �768 projector, and if you are including some text along withyour image, you will probably only need an image that is 800 �600. When you insert a large image into PowerPoint, you“drag” the corners to shrink the image to fit. However, Power-Point stores the entire image, and it has to resize it every time itis displayed. The two consequences of using large images inPowerPoint are that the size of the presentation rapidly en-larges, and the presentation slows down while the host com-puter (sometimes much, much slower than the one you writethe presentation on) reads the large file from the (slow) CD-ROM and then resizes the image “on the fly.” For images I amgoing to project with PowerPoint, I first resize them to 800 �600, and then increase their brightness and contrast to makethem project better. I then save them as mid-grade JPG files tosave space, and append “-ppt” to the file name (“myfile.jpg”becomes “myfile-ppt.jpg”). This way I know that the file hasbeen developed and tuned for a PowerPoint presentation.

When emailing images, I always assume that the recipient hasdialup service, and do not attach too many or too large images.Unless the recipient has requested a high-resolution image, Isend lower quality JPG files in resolutions of 640 � 480. Also,do not forget your upload times because even “fast” non-dialupservices like DSL, Cable, and Satellite are asynchronous andupload more slowly than download. Many surgeons belong to“listserv” broadcast mailing lists. These are very effective toolsfor sharing information and questions rapidly across the coun-try. However, it is considered poor form to attach image files tobroadcast mailings. Most listservs have a common websitewhere the moderator will post an image on a web page forinterested individuals to view.

When it comes to hardcopy output (desktop printing, pho-tofinishers, or journal submission), the working term is “dotsper inch” (dpi). The digital image contains rows and columns ofdots. How tightly packed together these dots are placed on theoutput paper determines the size of the final print. For example,an image with a resolution of 1800 � 1200 pixels will be 6“ �4” (1800/300 � 1200/300) when printed at 300 dpi, (3“ � 2”if printed at 600 dpi, etc.). The dots-per-inch is sometimes

specified within the image, but it is easily changed within thegenerating program or overridden by the printer’s softwaredriver. Many programs assume screen output (the average mon-itor has a dpi of 72 to 96 dpi). If the image above was printed at72 dpi, the output would be 25“ � 17”! Although 300 dpi wasthe “holy grail” of laser printers a few years ago, 600 or 1200 dpiis the laser standard today. Most inkjet printers print at 720 dpior higher, and some claim 1440 dpi in at least the horizontaldirection. Personally, I really cannot see any practical differencebeyond 600 dpi, and current limits on storage, data transfer,and processor power make handling images beyond 600 dpiimpractical. For instance, an 8 � 10 image, at 600 dpi, in “truecolor” has a raw data file of over 86 megabytes. (Remember thata 35-mm slide has around 5 MB of data available.) PhotoShopmanipulations are slow on images of this size, even on a high-end consumer system.

What happens when you take a 2.2 MP image (1800 �1200) and ask your printer to make an 8 � 10? At this size, theimage needs between 150 and 180 dpi to print, so your fancy720-dpi printer will wind up using about 16 drops of ink tomake a single dot on the page (720/180 � 4, and 4 � 4 � 16).Smart software or printer drivers will vary the colors of these 16droplets to smooth the transitions between pixels, which in-creases the perceived quality of the printed image, but adds nodata. This technique is called “interpolation.” Well-done inter-polation can make a very acceptable 8 � 10 printout even froma 2.2 MP image. I take my 1800 � 1200 Coolpix 950 imageand carefully hand-tune it with PhotoShop into a 600 dpi,6000 � 4800 pixel file, with judicious application of filters toimprove brightness, contrast, sharpness, and image coloration(tone). I then either print it on my desktop printer or send it toan online service.

Digital photofinishing is now common. What began on theInternet has found its way into the traditional “one-hour” labs.Get them the digital file (either via upload for the online ser-vices, or handing them a CD-ROM or memory card for thelocal laboratories), and they produce the same print they wouldproduce from a film-based image by projecting the digital fileonto photosensitive paper. These images have the same qualityand durability as those done from film. I rarely print photo-graphs from my desktop printer, as those done by an onlinephotofinisher are better and usually cheaper. If you wonder ifdigital photography has finally “won” over film-based photog-raphy for the average amateur, you need look no further thanKodak. My favorite online digital photofinisher, Ofoto.com,was recently bought by Kodak!.

Medical journals have accepted digital manuscripts for years,but many still wanted multiple 5 � 7 glossies for their printersto use. Some still want the glossies for use as “reviewer’s copies,”but increasing numbers will accept JPG files, allowing digitalsubmission of manuscripts via email with Microsoft Word andJPG files. This is, in fact, how this article got into print! Fewjournals print images much larger than 2 � 3 inches, so even at

586 CURRENT SURGERY • Volume 59/Number 6 • November/December 2002

Page 7: Practical digital photography for surgeons

600-dpi printing, the file only needs to be 1200 � 1800 (2.2MP). Because most digital cameras now exceed 3 MP, it is easyto produce acceptable images for journal submission.

SUMMARY

Digital photography is now sufficiently capable of replacingfilm-based imaging for the average amateur photographer. It

should replace film-based photography for the surgeon. Under-standing the pixel and how it is generated, manipulated, saved,and output is essential to successful digital photography andimaging. The surgeon’s camera should be especially capable inthe areas of portability, use in the operating room, close-focusabilities, slide-stand use, and 35-mm slide copying. Archiveyour original images onto CD-ROM, hand-tune them specificto the eventual display medium, and enjoy!

CURRENT SURGERY • Volume 59/Number 6 • November/December 2002 587