Informatics

An Introduction to Digital Cameras

Andrew Zura, M.D., Ali Jahan, M.D., and Judith Hass, M.D.

Background and Objectives: People in all walks of life are using digital cameras instead of the traditional filmcameras. Reasons include simplicity of use, ease of development, ability to incorporate the pictures intodocuments, potential to edit the pictures easily, and capability to send them by e-mail. This article will brieflydiscuss digital cameras, how they work, what they can do, and what you should look for in one.Editor’s Note: This is the fourth in a series of articles demonstrating and describing information technology.The articles include nontechnical information and are geared toward the computer novice with interest inregional anesthesia and pain medicine. Reg Anesth Pain Med 2001;26:164-168.Key Words: Digital camera, Photography, Computers.

How Is a Digital Camera Different Froma Regular Camera?

F ilm used in conventional cameras consists ofmillions of light-sensitive, silver halide crystals.

These crystals become exposed to light when thecamera’s shutter opens. When exposed, these crys-tals instantly react to the light and capture areas ofbrightness, darkness, and color as represented byyour subject. To produce pictures from the film,chemicals are added to stabilize the film so that thecrystals are no longer sensitive to light. This resultsin what we all know as negatives. This processallows you to see what you have captured with thelight areas representing dark, and vice versa (hencethe term “negative”). To print the picture, light isprojected through the negative onto light-sensitivepaper, where dark and light are reversed. The paperis developed in a similar fashion as film, and theresults are your prints. The quality of the photo-graph comes from its “resolution.” The greater thenumber and density of the silver halide crystals, theincreased richness and realism of the photograph.1

Digital cameras, on the other hand, do not usefilm. Just like a traditional film camera, a digitalcamera’s shutter admits light when you take a pic-ture. Your subject is instantly recorded onto light-sensitive material composed of millions of tiny elec-tronic sensor cells or pixels. The camera adjusts the

light captured by the cells and corrects for balanceand color. Then, just as quickly, the camera trans-lates these corrected values into digital code.2 Thequality of a digital picture is also based on resolu-tion, just like a traditional camera. However, in thedigital world, resolution is determined by tiny elec-tronic squares called pixels; the more pixels, thehigher the resolution.

Once you download these pictures from the cam-era to your computer, you can do many things withthem. They can be stored like any piece of software,printed through your computer printer, e-mailed,placed in PowerPoint slide presentations, or trans-ferred to a website. They are easily edited withstandard software and, since the picture is digital,the first copy will look just a good as the next.

Both types of cameras have their advantages.Film cameras cost much less than a similarlyequipped digital camera and can quickly take oneshot after another without the processing delaysbetween shots that most digital cameras have. Dig-ital cameras, on the other hand, reduce the delay offilm processing and provide immediate access to theimages. Also, it is much easier to edit pictures witha software package than in a dark room.3

Digital Cameras Do Not Have Film, So How DoThey Store Pictures?

Because the pictures that a digital camera makesare computer files, the camera needs to store themin a manner similar to that used by your computer.Cameras can store pictures using an internal per-manent memory chip or a removable memory de-vice that can be exchanged like a roll of film.

The memory capacity determines the numberand quality of images that you can take with yourdigital camera. Once the capacity is reached, you

From the Department of General Anesthesiology, The Cleve-land Clinic Foundation, Cleveland, Ohio.

Accepted for publication March 18, 2000.Reprint requests: Andrew Zura, M.D., Department of General

Anesthesiology, The Cleveland Clinic Foundation, 9500 EuclidAve, E31, Cleveland, OH 44195. E-mail: zuraa@ccf.org

© 2001 by the American Society of Regional Anesthesia andPain Medicine.

1098-7339/01/2602-0013$35.00/0doi:10.1053/rapm.2001.20771

164 Regional Anesthesia and Pain Medicine, Vol 26, No 2 (March–April), 2001: pp 164–168

will need to download the pictures onto your com-puter before taking more pictures. So, if you areclose to your computer or plan to take only a smallnumber of pictures, less storage memory will suf-fice. However, if you plan on taking a sight-seeingtour of Europe, you want to make sure that youhave enough storage to last the whole trip. Twomegabytes (MB) of memory will capture anywherefrom 10 to 50 photos, depending on the resolution,while 4 MB of memory can store about 70 pictures(Table 1). The authors recommend at least 4 MB ofmemory. Ideally, the camera should have the capa-bility of using a removable memory device. Thisoption is important to ensure that there will always

be enough storage available. The type of storagedevice your camera uses depends on the manufac-turer of the camera and is not interchangeable withother digital cameras. There are a number of differ-ent types of storage media available, each with ad-vantages and disadvantages4,5 (Table 2).

To conserve memory, some cameras come with aliquid crystal display (LCD) viewfinder (see below)that will allow you to immediately preview pictures thatyou have taken so you can delete unnecessary images.

What Features Should I Look for in aDigital Camera?

Resolution. This is important because thequality of an image depends on its resolution. Thenumber of data points that make up the imagedetermines the resolution. These data points arecalled pixels. The larger the number and smaller thesize of the pixels, the greater the image and detail ofthe digital photograph. The resolution capabilitiesof a digital camera are expressed in one of twoways—the sensor’s dimensions in pixels or by itstotal number of pixels. For example, a camera’sresolution can be described as being 1,200 � 800pixels (pronounced “1200 by 800”) or 960,000 pix-els (1,200 multiplied by 800). The authors currently

Table 1. How Many Pictures Is That?

Depending on the storage format, you can expect anywherefrom one 640 � 480 pixels image to one 1,600 � 1,200image to occupy one megabyte of storage space (0.3 to 2megapixels per MB). The wide variance is due to the mannerin which pictures are stored and how highly they arecompressed. Very rough ballpark estimates would suggestthe following nominal numbers of pictures per megabyte ofstorage, assuming only modest compression for a high-quality image:640 � 480 � 5800 � 600 � 31,024 � 768 � 21,280 � 1,024 � 1

Table 2. Removable Storage Type and Capacity

Floppy Disk: 31⁄2-inch floppy disks are used in some cameras, such as the Sony Mavica (Sony Corp, Tokyo, Japan) line. Thisstorage medium offers 2 advantages: foolproof transfer to personal computer and cost. Disadvantages include bulky physical sizeand a limit of 1.4 MB of storage. ($0.30/MB)

SuperDisks (Imation Corp, Oakdale, MN): The SuperDisk is equivalent to a giant 120-MB floppy disk, which Panasonic (MatsushitaElectric Industrial Co, Ltd, Osaka, Japan) is using for some of its cameras. At 15 cents per MB, it’s cheap storage. While itmitigates the limited storage problem of the standard floppy, it does not address the physical size issue. Cameras using either ofthese 2 media must be at least 4 inches square just for the drive mechanism, exclusive of all optics and electronics. ($0.15/MB)

Compact Flash Cards (SanDisk Corp, Sunnyvale, CA): These solid-state devices are about the size of a matchbook and featurelarge storage capacities, up to 512 MB. They are not magnetic media, but rather nonvolatile programmable memory, like the BIOSchips in computers. If you have ever “flashed a new BIOS,” you have used flash technology. Unlike RAM chips, these cards do notneed a constant source of power to retain their memory. When slipped into a PC Card (PCMCIA) adapter, these cards can be readdirectly via a laptop computer’s external PC Card slots. CompactFlash cards enjoy tremendous popularity among laptop usersbecause of their speed and ease of use. CompactFlash card readers are available for desktop computers as well. ($1.75/MB)

SmartMedia (SanDisk Corp): Used extensively by Olympus (Olympus Optical Co, Ltd, Tokyo, Japan) and others, this medium is aflash technology device, like the CompactFlash cards above. Matchbook-sized but as thin as a credit card, size and weight are thebiggest advantages of this medium. When first introduced, these cards were limited to storage sizes of 2 to 4 MB of data, but theyhave since increased in capacity up to 128 MB. The card can be inserted into a floppy adapter and then read like a standardfloppy disk. These cards can also be inserted into a PC Card adapter as with the CompactFlash cards above. SmartMedia readersare also available to read the cards directly. ($1.65/MB)

Memory Sticks: A Sony invention, Memory Sticks are the size of a stick of chewing gum. Similar to a CompactFlash card and withstorage sizes up to 64 MB, Memory Sticks are currently the big question mark in storage. Marketed as part of a “personalnetwork,” nearly every Sony product has a Memory Stick port, so data can be shared seamlessly between many disparate devices,from VAIO (Sony Corp) laptops to MP3 players (MP3.com, San Diego, CA) to AIBO (Sony Corp) the robot dog to a desktop pictureframe that runs slide shows. Digital images can be plugged directly into a Memory Stick enabled printer and printed, for example.Cost is currently higher than other flash media, but as more manufacturers license the technology, prices will fall. Memory Stickreaders, PC Card adapters, and floppy disk adapters are already available to ease the movement of files to computers. ($3.00/MB)

MicroDrives: IBM (Armonk, NY) has introduced a miniature hard drive that shares the same form factor as (CF�Type II)CompactFlash cards. With a platter the size of a quarter, the MicroDrive operates like any other magnetic hard drive, with storagecapacities up to 1,000 MB (1 GB) currently available. Best for situations where large numbers of very high-resolution photos needto be stored. Its biggest disadvantage is cost, although the cost per megabyte makes it a relative bargain. ($0.80/MB)

CD-R Discs: The newest storage device to hit the market, CD-R discs hold 156 MB on a 3-inch disc. Their biggest advantages arecost and the fact that the CD-R disc can be read instantly in virtually any CD-ROM drive. Their biggest disadvantage, aside fromthe size issue, (see Floppy Disks above), is that the discs are not reusable. At this price, who cares? Their second biggestdisadvantage is that they are used in only one camera out there—a Sony Mavica at $1,300. ($0.03/MB)

Data from ref 5.

An Introduction to Digital Cameras • Zura et al. 165

recommend cameras with at least 1 million pixels;these cameras are also called megapixel cameras. Itis possible to get cameras with resolution of up to asmuch as 6 million pixels, but realize that the cost ofthe camera will also increase.6

Most cameras have the capability of adjusting theresolution, thus allowing you to shoot more infe-rior-quality pictures or fewer, better-quality pic-tures. We recommend shooting in the higher-qual-ity mode because the resolution that is lost inlower-quality modes can never be regained. Whencreating photographs from digital pictures, the res-olution that you initially obtain will determine howmuch you can enlarge it before it becomes grainy.Table 3 is a guide to the resolution of the digitalpicture needed to make a print of a certain size.

Zoom. The fixed-focus lenses on many digitalcameras are adequate for landscape and group pic-tures; however, if you plan on photographing peo-ple, you definitely need a camera that incorporatesa zoom lens. The ability to “zoom” is a tremendousadvantage for “tighter” images. A 2� zoom roughlydoubles the size of your subject. Ideally, the zoomshould be optical, not digital. With an optical zoomthe camera adjusts the lens to focus tighter overthe entire sensor of the camera, so the cameracaptures the zoomed area in its highest resolu-tion. With a digital zoom, the camera ignores allof the data collected except for the intendedtighter image; thus, these cameras do not increasethe resolution of the portion of the picture thatyou want to keep.7

Viewfinder. A viewfinder displays the imagebeing photographed. There are 2 types of viewfind-ers, with the majority being optical viewfinders.The optical viewfinders display a straight-line viewof the scene that you are photographing. You donot see through the lens, so you cannot tell if theobject is in focus. Additionally, the window isslightly offset from the lens; thus, a close-up imagewill probably be slightly offset. The other type ofviewfinder offers thru-the-lens viewing. The light

passing through the lens is split by a prism so thatpart of the light displays the image on the view-finder and the remainder passes to the light sensoron the camera. This is the “what you see is whatyou get” viewfinder. For the majority of people, thesimple optical viewfinder is sufficient. The cost ofthe thru-the-lens viewfinder does not justify theadvantage of seeing exactly what the lens sees.Most digital cameras have autofocus, so focusing ofthe lens is not a real issue either. A good viewfinderwill have a wider field of view than just the picture.This allows you to anticipate your subject’s actionsbetter because you can see them before they enterthe actual picture area.8

LCD Screen. The LCD is a small, color, pre-view screen that is built into the camera. The screenranges from 2 to 3 inches and serves a number ofpurposes, including being able to preview a picturebefore you take it and review images you havetaken. If the image is not adequate, you can deleteit and immediately take it again. Also, the imageyou see on a preview screen is taken directly fromthe image sensor, so it is a true thru-the-lens view.Although you can use it to compose photos as youtake them, this is not effective. These displays tendto heavily utilize battery power; thus, it is best tokeep them turned off and use the optical viewfinderfor taking pictures. There are a few situations inwhich the preview screen becomes indispensable.For close-ups, the preview screen is a great way tocompose and focus the image because it shows ex-actly the same image you will capture. Additionally,when photographing over a crowd, or around acorner, you can compose the image without hold-ing the camera up to your eye.8

Battery Life. Digital cameras depend on bat-teries for power to operate and use them rapidly.The LCD display and the flash heavily utilize batterypower. To keep battery costs low, we recommendrechargeable batteries (nickel cadmium) and a bat-tery charger. An alternating current (AC) adaptermay also be useful for operating the camera if bat-

Table 3. Maximum Image Resolution

320 � 200 pixelsand below

“No res.” While unsuitable for print media, these “no-resolution” formats have found a niche on the Internet,from video to small still photos. File sizes are miniscule, making them ideal for web use.

640 � 480 Low res. Generally, the lowest resolution image on today’s video cameras. At this resolution, images would fillthe screen of a 14-inch computer monitor. In print media, these photos would be limited to thumbnails, buton the Internet, they are already large photographs.

800 � 600 Medium-low res. Fills the screen of a 15-inch monitor. Suitable for 2 inch � 3 inch to 3 inch � 5 inch prints.Resolutions higher than this are generally unsuited for the Internet or for viewing on typical computermonitors in general.

1,024 � 768 Medium-high res. Fills the screen of a 17-inch monitor. Suitable for 3 inch � 5 inch to 5 inch � 7 inch prints.1,280 � 960 High res. Fills the screen of a 19-inch monitor. Suitable for 5 inch � 7 inch to 8 inch � 10 inch prints.1,600 � 1,200 Very high res. Fills the screen of a 21-inch monitor. Suitable for 8 inch � 10 inch prints and above.1,920 � 1,600

and aboveProfessional use, mostly. Storage and processing requirements preclude using these resolutions routinely.

Suitable for demanding applications that require the maximum detail and where cost has little bearing.

Data from ref 11.

166 Regional Anesthesia and Pain Medicine Vol. 26 No. 2 March–April 2001

teries run out. We also use the AC adapter anytimethat mobility is not an issue (e.g., for downloadingthe pictures to a computer).9

Ease of Download. The method(s) availableto download your pictures onto your computer isan important feature. It can be as simple as placinga disk in your computer or as difficult as adjustingthe computer operating system to activate the de-sired communication ports. Some digital camerasoffer more than one means of downloading yourimages (Table 4). The authors recommend the 3.5-inch diskette and the Universal Serial Bus (USB).These two methods are superior with regard tosimplicity and speed. Nothing is simpler than plac-ing a 3.5-inch diskette with the pictures into thecomputer. The USB port is the fastest of the down-load modalities. Most cameras can use the serialport for download because it is relatively simple,but it may be very slow.

How Do I Work With My Digital Pictures?

Software. Once the image files are in thecomputer, they can be edited with one of themany editing software packages available. Mostcameras come with a basic image transfer andediting utility.3 If you purchase a less expensivedigital camera, it is likely that the software pack-age is an older version. Standard photo editing ispossible with the older software; however, theautomatic option of posting your photos onlinemay not be possible. Some easy-to-use packagesare Microsoft Picture It 2000 (Redmond, WA) andMGI PhotoSuite III Platinum Edition (RichmondHill, Ontario, Canada). Consider one of thesepackages if the software that came with yourcamera is inadequate.9

Printers. If the goal is to print text in addi-tion to photographs, a standard inkjet printer(e.g., HP DeskJet [Palo Alto, CA], Epson Stylus[Long Beach, CA], Canon BubbleJet [Lake Suc-cess, NY]) will do. They do a reliable job of print-ing photos, especially on special paper, but theirmain job is text and simple graphics. However, if

Table 4. Techniques to Transfer Images tothe Computer

Floppy Disk: The easiest method to use, but with limitedstorage. Many computers are no longer shipping with floppydrives. Data transfers are almost as fast as USB below. Idealfor moving a picture or two very simply.

Floppy Disk Adapters and SuperDisks: Easy to use, highercapacity than floppies, with slightly more setup requirements.Usually requires installation of some software on a one-timebasis. Equivalent to a floppy disk in speed.

Serial Port: Available on all computers. Requires a cable toconnect the camera to the computer. Slowest of all transfermethods, not much faster than a good telephone modemconnection to the Internet. If you need to mate your camerato an unknown computer somewhere, this will work mostevery time. Most cameras can be controlled from thecomputer over a serial port.

Parallel Port: Available on all IBM-compatible computers(Armonk, NY). Requires a cable to connect the camera tothe computer. Faster than a serial port but not as fast as afloppy disk.

USB port: Easiest to set up properly (when things work right).Available on many newer computers or can be added toolder ones at a low cost. Requires a cable to connect thecamera to the computer. An order of magnitude faster than aserial port, about the speed of an Ethernet connection to theInternet, making it one of the better cheap solutions. Mostcameras can be controlled from the computer over a USBport.

IEEE-1394 (FireWire [Apple Computer, Cupertino, CA]): Ahigh-speed port (at least 3 times faster than USB) similar inspeed to cable modems. FireWire not only passes imagedata, but frame accurate camera control and audio as well.Built into some newer Macintosh (Apple, Cupertino, CA)computers as well as the Sony VAIO (Sony, Tokyo, Japan)laptops. For $100, can be added on to any desktopcomputer fast enough to keep up with it. Essential for video,less so for still photography. Cable required.

PC Card: This interface is suitable for only those devices thathave PC Card slots, like laptops. The benefits are its speed(equivalent to USB) and its ease of use. No cable isnecessary.

IrDA Port: Infrared transmission without a cable. Benefits areease of use and portability. Drawbacks are availability limitedmainly to hand-held devices, plus a “line-of-sight”requirement. Speed is about 5 times faster than a standardserial connection, half as fast as USB.

Data from refs 11 and 12.

Table 5. Places on the Internet to Learn AboutDigital Cameras

Kodak Digital Learning Centerhttp://www.kodak.com/US/en/digital/dlc/

Short Course in Selecting a Digital Camerahttp://www.shortcourses.com/choosing/contents.htm

Short Course in Digital Camera Photographyhttp://www.shortcourses.com/book01/contents.htm

PC Photo Review–Digital Camera Resourcehttp://www.pcphotoforum.com/

Imaging Resource–Digital Imaging Resource on Webhttp://www.imaging-resource.com/

How Digital Cameras Workhttp://www.soundvisioninc.com/howdcw.htm

Digital Photography Reviewhttp://photo.askey.net/

Active Buyers Guidehttp://www4.activebuyersguide.com/abg/nav/

StartPageHandler.cfm?PID�1A0A04%2DF24AFB868D7C8CFDA3F80C7988A8C2B7&CatID�2&option�Basics�First&&RefID�0

Table 6. Consumer Resources Information on theInternet

20-20Consumer(http://www.20-20consumer.com/digitalcameras/):Independent consumer pricing site listing the best prices fordigital cameras and accessories.

Consumer World (http://www.consumerworld.org/): ConsumerWorld is a public service site that has gathered over 1,700 ofthe most useful consumer resources on the Internet andcategorized them here for easy access.

eSmarts (http://www.esmarts.com/): eSmarts is a consumerguide to Internet shopping.

Product ReviewNet(http://www.productreviewnet.com/home.html): Type DigitalCameras into the Search field and get a list of magazinereviews about digital cameras.

An Introduction to Digital Cameras • Zura et al. 167

you plan on printing a large number of photo-graphs, consider buying a photo printer. Thereare 2 general types. The small dedicated photoprinter that prints on 4 � 6 sheets of paper havedesirable outputs but are expensive to buy andmaintain. Then there are the full-sized photoprinters like the Epson Stylus Photo printer andthe HP PhotoSmart. These use letter-sized paperand do amazing work on glossy or coated paper.However, these supplies are also expensive. Notethat these printers are not quite as good with textas are general printers.10

Where Can I Find Additional Information AboutDigital Cameras?

The Internet offers a number of excellent sites forinformation about digital cameras (Table 5). The

ShortCourses site gives an excellent introductioninto how digital cameras work and how to shop forone. There are a number of sites dedicated to thehobby and occupation of digital photography suchas PC Photo Review, Digital Photography Review,and Imaging Resource. In addition to tips on digitalphotography, they offer reviews of new camerasand gadgets, frequently asked questions, forums,and buyer’s guides to aid you in determining whatkind of options you need in your digital camera.Finally, realize that almost all digital camera ven-dors have their own website advertising their prod-ucts and detailing their characteristics. A good ex-ample of a company website is the Kodak site, which hasa significant amount of education material.

Where Can I Buy a Digital Camera?

When purchasing a digital camera, checking theprices online may serve you very well when com-paring with a traditional store. There are severalwebsites that locate products at their least expen-sive prices. The authors currently recommend 20-20Consumer as the site with an easy-to-use inter-face that locates good prices and has customerratings on the different retailers. Sometimes youcan save as much as 30% to 40% when comparedwith a traditional retail store. Table 6 contains anumber of consumer information resources. Fi-nally, we recommend reading multiple reviews oncameras to obtain a variety of viewpoints. A websitethat will particularly aid you in this is Product Re-view Net. It is a site that indexes and summarizesproduct reviews from many reliable sources.

References

1. http://www.kodak.com/global/en/consumer/digitalBridge/howFilm.shtml

2. http://www.kodak.com/global/en/consumer/digitalBridge/howDigital.shtml

3. http://www.zdnet.com/computershopper/stories/howtobuy/0,7167,2252033,00.html

4. http://www.zdnet.com/computershopper/edit/howtobuy/dcstep3.htm

5. http://www.buybuddy.com/sleuth/6/1/10203/54/?page�3

6. http://www.shortcourses.com/book01/chapter02.htm

7. http://www.zdnet.com/computershopper/stories/howtobuy/0,7167,2252039,00.html

8. http://www.shortcourses.com/choosing/09.htm9. http://computers.cnet.com/consumerelectronics/

0-1078-7-1463355.html?tag�st.co.107810. http://www.dcresource.com/faq/faq.html11. http://www.buypath.com/bguide/d.camera.8.shtml12. http://www.buybuddy.com/sleuth/6/1/10203/54/

?page�413. http://www8.activebuyersguide.com/abg/nav/

Glossary.cfm?PID�78x8x35x1848x3618&Ca�D�2

Appendix. Digital Camera Terms

Auto Flash: A flash that fires automatically whenever existingambient light is insufficient for a good picture.

Auto Focus: A feature that brings the center of the field ofview into sharp focus.

Compression: A method for reducing storage requirements fora picture. The tradeoff for higher compression is lower imagequality. Some methods of compression are better forphotographs than others. BMP and TIFF files use virtually nocompression and eat up tremendous storage space. JPEGcan selectively compress by percentage to “fine-tune” animage. It accomplishes its magic by throwing awayunnecessary data (lossy compression). GIF compresseswithout throwing away any information (losslesscompression), but it works poorly with photos althoughgreatly with line art.

Delay Between Shots: Also known as lag time, this is thedelay the camera imposes on the user due to limitations inprocessing and storage speed. Generally measured innormal mode at the camera’s maximum resolution.

Image Capacity: The number of pictures you can take beforerunning out of storage space. A somewhat meaninglessnumber if a resolution is not also specified. (See Table 1.)

Images at Max Resolution: A better method of expressingimage capacity. This is the absolute fewest number ofpictures your camera can store (worst case scenario).

Images at Min Resolution: Related to the term above. This isthe absolute highest number of pictures your camera canstore (best case scenario).

LCD Display: A small display device used to project pictures,analogous to a small projection television. A nice feature tohave for times when the camera must be positioned in sucha way that you cannot look into the viewfinder. Essential foron-camera editing (see below).

Mini-Movie: A feature on some cameras that allows them tofunction like a video camera for a few seconds at a time byrapid-firing a sequence of pictures. This is most analogous tohigh-speed motor drive units on high-end film cameras.

On-Camera Editing: A feature that allows you to view yourpictures directly on the camera through the viewfinder or asmall LCD display. This feature allows you to delete photosthat you don’t want, freeing up storage space.

Resolution: Digital images are comprised of many little dotscalled picture elements, or pixels for short. Resolution isdefined as how many pixels there are in any given image(see Table 3). As expected, the more pixels there are, thesharper the image. The trade-off is the more pixels, thehigher storage and processing requirements. This can beoffset somewhat with compression (see above).

Data from ref 13.

168 Regional Anesthesia and Pain Medicine Vol. 26 No. 2 March–April 2001