On October 14, 1839, a French physician named Alfred Donne reported to the Parisian Academy of Sciences with an astonishing item; a daguerreotype depicting the eye of a fly—the first known use of image capture technology in science and medicine

In the following decades, this technology and its progeny would become an indispensable part of modern medicine. The Kodachrome, color slide film developed (pun, sadly, intended) by Eastman-Kodak in 1935, served as the gold standard for decades, both within the medical industry and in society at large. Physicians and other healthcare professionals made use of pictures and photographs to train medical students, improve the detail of patient records, and even to assist in the evaluation of certain conditions. For the dermatologist, responsible for confronting a vast assortment of skin diseases, lesions, and other disruptions of personal topography-often distinguishable from one another only by minute visual detail-pictures would prove particularly powerful. The evolution of photographic technology has proceeded at a drastically accelerated pace since the early 1980's, when Sony released the Mavica-the first digital camera to reach the market. The early digital cameras were not terribly practical, especially not for use in medicine. They were extremely difficult to use, and the images they produced were far too indistinct to be of diagnostic value. However, in the last decade, the tech industry has released dozens of updated digital cameras every year, each representing a small but significant improvement over its predecessor. Gradually, the medical community, and the dermatology community in particular, is becoming increasingly interested in digital photography (DP). Broadly speaking, the difference between conventional (analog) photography and DP is that while the former employs film and a complicated chemical process to store visual information in print form, the latter stores the same information electronically, as a computer file. In DP, no physical "photograph" is produced, and no film is required.

No, you don't. Trust us. The advantages of DP in the medical setting, particularly given the advanced state of the technology, are too numerous and significant to ignore. They include:

Cost-Efficiency: The initial cost associated with DP-the purchase of a digital camera and accessories-is usually slightly higher than that associated with conventional photography; digital cameras, particularly advanced models, can be expensive. However, conventional photography is actually far more expensive in the long run, because digital photographers incur no incremental costs. Remember: you won't need film for your digital camera, nor will you need to pay to develop your pictures; taking and viewing 20,000 pictures will cost you only a few dollars more than taking and viewing 20 (and even that difference is attributable only to storage costs-see below). Because digital photos show up on the camera's built-in LCD display screen as soon as they are taken, you can see immediately whether the picture is adequate, and delete it if it's not. You can take 50 pictures before you get one right, if you wish; try the same with a film-based camera, and you'll find incremental costs piling up quickly.

Speed: Because they do not require development, digital photographs are available the minute they are taken (as a bonus, they are never lost, stolen, damaged, accidentally exposed).

Quick Recall: Because they are electronic files, digital photos can be arranged in a database using cataloguing software, such as Adobe Photoshop Album; this makes organization easier and retrieval much, much faster.

Durability: Once again: they're computer files. Digital photos don't degrade with time, and won't be lost in an office fire; assuming you backup your files on a regular basis, they should last more or less forever.

Image Editing: Using appropriate editing software, you can adjust brightness, contrast, and the like, crop pictures, add labels, or enlarge relevant portions of an image to your heart's content. Some physicians may also edit images in order to demonstrate graphically to patients what a lesion or condition may look like post-treatment; this form of image manipulation is governed by very strict ethical standards from the American Academy of Dermatology (sidebar).

Easy Consultation and Referral: Physicians can easily send digital images to colleagues if the patient or the doctor desires a second opinion. When a patient changes providers, electronic images can be more easily, quickly, and reliably transferred than printed images.

Teledermatology: Way back in 1999, a team of investigators at the University of Arizona College of Medicine in Tucson conducted a study comparing the diagnostic accuracy of dermatologists making patient evaluations based on in-person examinations with that of dermatologists asked to evaluate based only on digital photographs.

The results-published in the Fall 1999 issue of the Telemedicine Journal-confirmed that physicians were able to maintain high diagnostic accuracy rates even when making judgments from digital photographs. These findings may have extraordinary implications for individuals with dermatologic conditions requiring regular monitoring who live in underserved areas, or who have disabilities that make frequent office visits impractical or impossible. Using a digital camera, such patients could document their condition and transfer the information to their dermatologist in real-time, who could then make an evaluation and recommend treatment. This practice, called "teledermatology" is part of a growing but still controversial trend toward "telemedicine" in the United States. Some physicians feel that Internet-based interaction with patients can greatly supplement traditional management, while others fear that impersonal "virtual consultations" may erode the quality of care; watch this space for more on this debate in months to come.

The most frequently cited reason for preferring conventional photography to DP is image quality; the best digital cameras fall somewhat short of the quality achieved by the best analog cameras. To explain why, it is necessary to (briefly) explain the nature of a digital photograph. See the chart at the end of this article for specs on this and other digital cameras.

The chief unit of measurement in digital photography is the pixel, short for "picture element." A pixel is a very tiny dot of a single color; many thousands of pixels, arranged in a matrix, comprise a digital image. What's important to understand for our purposes is that the color (and brightness) of any individual pixel is deterministic; that is, each pixel is one color and one color only. This can make it difficult to accurately represent smooth gradations of color, because pixels are, at least on a relative scale, fairly large units of composition. By way of contrast, color and brightness in an analog photo, which is a chemical creation, can vary nearly on the molecular level. The upshot is that analog photography is capable of incredibly precise detail to a degree currently unachievable by digital photography, although most users won't notice the difference.

What users will notice is that digital photos are much more prone to certain kinds of errors than their analog counterparts. For example, if you are taking a picture of a high-frequency pattern, like a plaid shirt or an extremely colorful lesion, some cameras may not be able to represent the full range of colors and substitute false ones instead, a process called aliasing. Another type of error, the presence of artifacts, is most noticeable with gradations of color as described in the preceding paragraph; unable to represent the smooth transition from color to color, some cameras will simply display a series of distinct bands of color instead.

The drawbacks outlined above have kept many professional photographers, for whom accuracy across a broad range of subjects is paramount, from switching to digital photography. For the purposes of the clinical dermatologist, however, they are unlikely to have an impact significant enough to outweigh the advantages of DP.

Creating a digital photography studio in your office entails much more than simply buying a camera. There are a number of unique equipment needs you'll have to consider, including storage, software, and printing devices, all with a range of choices that will vary considerably depending upon the uses to which you plan to put your photography. Also, you might want to remember to buy a camera.

Remember, although DP differs in many ways from traditional photography, the basic principles of good photography still apply: be sure lighting is adequate and appropriate, use neutral backgrounds, and be sure to use the same lighting and backgrounds for pictures when tracking a condition over time.

Step 1: The Camera
CNET (www.cnet.com), the Internet's premier hardware review site, lists a staggering 500 different models of digital camera currently or soon-to-be available for purchase, each with an array of specifications and features sure to baffle all but the most ardent photography enthusiast. Any discussion of the relative merits of cameras must begin with resolution, which measures the clarity of the pictures each camera takes. Resolution is measured by the maximum absolute number of pixels across the width and height of the picture, usually represented in the form "N1 x N2." For example, a camera with a maximum resolution of 1000 x 1400 can capture and display a maximum of 1,000 pixels of information from left to right, and a maximum of 1,400 pixels from top to bottom. Again, this number is absolute; in the case described above there can be no more than 1,000 pixels from left to right, whether the picture itself is 5"x7" or 8.5"x11". Consequently, an image that displays with perfect clarity at the former size may look obviously pixilated if enlarged.

A handy stat used for measuring the overall clarity of a given picture is dots-per-inch (DPI), which is calculated by dividing the total number of pixels by the total number of inches they cover.

In the example above, if a picture taken at resolution 1000 x 1400 is displayed at 5"x7", its image clarity would be 1000/5 by 1400/7, or 200DPI. An article by D.M. Siegel, published in the September 2002 issue of Seminars in Cutaneous Medicine and Surgery, demonstrated that such a resolution is adequate for dermatologic purposes if the picture is used only for onscreen display with 5"x7" image size. If you want to view images larger than 5"x7", you'll need a camera with better resolution in order to reduce the risk of pixilation. The same is true if you want to be able to print your images. Standard print quality is 300DPI, which means you'd need a 1500 x 2100 resolution to print a 5"x7" photo, and even higher to print larger images. The vast majority of commercially available cameras are in the 2 megapixel range or higher; for more on this subject, see Ken Weiss' excellent article, located online at http://matrix.ucdavis.edu/informatics/digital-images/ digital.html.

Other characteristics important to dermatologists may include:

Sensitivity (ISO): This figure essentially measures how much light is required to produce quality images; cameras with lower ISOs will need more light to capture the same image, while higher ISO cameras are better equipped to capture images at high speed or low light (albeit with somewhat poorer color quality). Many modern digital cameras are equipped with flexible ISO.

White Balance: This feature allows accurate color capture under a variety of different lights. The user simply snaps a sample photo of a plain white background in each lighting condition, and the camera uses this information to adjust other colors accordingly.

Minimum Focus Distance: The dermatologist will often need to take pictures at extremely close range in order to capture important details; pay careful attention to this figure, as it will determine your ability to accomplish this.

LCD Display Size: The LCD screen is where you will see each picture and evaluate whether you need to take another. You'll want it to be large enough to allow you to assess each picture immediately.

See the comparison chart for a handy enumeration of the important features of a number of digital cameras currently available for purchase. Heaps of hardware reviews can be found at the aforementioned CNET, as well as at www.imaging-resource.com and www.dcviews.com.

Step 2: Storage
You won't need filing cabinets to house your digital photos, but you will need their virtual equivalent. Digital photographs can occupy an enormous amount of memory. Using a resolution of one megapixel, 10 images at 5"x7" would occupy roughly 20MB of storage space-1,000 pictures of this type would completely fill a 1GB hard drive! One way to deal with the storage problem is file compression, which comes in two basic flavors. "Lossless" compression, which usually converts the file into .TIFF format, reduces the size of the image file by a modest amount (5%-10%), but retains all the data of the original photo. "Lossy" compression, typified by conversion to .JPG format, makes for a considerably smaller file by discarding certain amounts of data. The type of image compression varies based on camera model. With file compression, a hard drive with a CDROM writer and 5-10GB of storage space should be more than sufficient to handle a sizable library of images.

On the subject of storage: you'll also need a memory card, onto which you'll save images from your camera for later transfer to your hard drive or CD-ROM (along with an adapter to manage this transfer). Memory cards and adapters are usually tied to the camera you purchase; ask that helpful fellow pestering you about an extended warranty to point you in the direction of what you need.

Step 3: The Rest of the Toys
A variety of other hardware and software products will be needed to make your digital studio complete. Image cataloguing and editing software, while not an absolute requirement, can be extremely helpful by allowing you to organize files, tag them with keywords, and search to find what you need. At the low end, Adobe's Photoshop Album (www.adobe.com/products/photoshop album/main.html) offers an incredibly intuitive interface and the ability to fix minor photo problems for around $50- see our article review at www.mdng.com/departments/may_ june2003/tech101.htm for more. The Image Library Manager (www.datasoft.co.uk/index.html) offers photo management software tailored toward physicians; Canfield (www.canfieldsci.com/imaging_software.html) produces products specific to dermatologists.

 If you plan to print your images, you will need a printer. Inkjet printers are typically the most cost-effective option, generally ranging in price from $100-$1,000, and producing pictures at near photo quality. Higher quality at a higher price can be obtained with a laser printer. Dye sublimation printers produce the highest quality images possible; but they do so slowly, and at a cost (from $500 up to $6,000) that seldom makes sense for the mostly infrequent printing needs of the dermatologist. What of all of the analog photos you've collected over the years? They can be added to your digital library if you invest in a scanner (check out ZD Net's product reviews at http://reviewszdnet. com.com/Scanners/2001-3136_16-0.html?tag=ont-scan). New analog photos can also be scanned onto a CD-ROM automatically by the developer if you request it when dropping off your film.

The future of digital photography in dermatology is limitless in potential. Used in combination with the Internet, DP can allow dermatologists worldwide to pool their visual resources into vast image libraries. Indeed, Johns Hopkins University-always ahead of its time in its employment of the Internet-already maintains an archive of more than 5,000 dermatologic images at http://dermatlas.med.jhmi.edu/derm. Teledermatology may one day make maintenance visits to the dermatologist's office a relic of an inefficient past. As digital images become digital videos, they will also allow for long-term tracking of skin problems, possibly in three dimensions; software may be able to automatically analyze digital images for specific clinical parameters.