NWA-PCUG Newsletter Article, May 2004
The Vice President's Report
May meeting topic - Taking Some of The Mystery Out of Digital Photography

by Bill Moeller
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An experienced backwoodsman once told me that there are statute miles, nautical miles, and forest service miles. His point was that distance alone does not tell the whole story on the trail. The same is true for resolution in digital photography; it is interesting, but it does not tell the whole story.

As used in digital photography, resolution refers specifically to the number of individual sensing elements in the sensing array that sits there in the focal plane and reacts to the image projected on it by the cameraís optical system--obviously an important factor in determining the quality of the final image, but by no means the only factor. Clearly, the quality of the projected image is equally if not more important, as is the design and construction of the array and its supporting software.

In some loose sense, the sensing array corresponds to the film in a conventional camera. Just as with film, each array design has its own individual color and tonal characteristics, as well as its own ability to render more or less detail in the final image. Further, just as with traditional photographic methods, the development process used affects each of these characteristics as well.

Unlike most film cameras, however, most digital cameras process the raw data from the sensors internally and deliver a final developed image to the photographer. With these cameras, you take what you get as far as development of the image is concerned. But with a small, but growing number of high-end cameras, the images are delivered in RAW format, and all development except the initial conversion from analog to digital is under the direct control of the photographer in the digital darkroom.

What does all of this mean you should look for in the way of resolution when selecting a digital camera? It means donít get too excited about resolution. Look for a camera that you like, that feels good in your hands, that you are able to use, and which takes pictures that you like. Beg, borrow, bum, or steal one and take it for a test drive. Then, before you buy, ask yourself whether resolution is likely to be a limiting factor in the kind of photography you do.

The best way to do this is to make a series of test prints at increasingly larger sizes and see for yourself where the image begins to get fuzzy or to lose its tonal continuity. But if you are like me and must engineer the decision, you can divide the length or width, in pixels, of the cameraís image by the corresponding dimension, in inches, of the final desired print. Conventional wisdom has it that 300 ppi (pixels per inch) will produce a fine quality print while 200 ppi will produce a very good print, assuming of course, a good original image and a good photographic printer. In some cases, somewhat less that 200 ppi can produce acceptable, but not exciting, prints.

Bottom line -- ignore the marketing folk, and make your own decision about how much resolution you need. The best way to do this is to run your own tests on the camera you are thinking of buying. You can narrow your search and get in the ballpark by doing a little arithmetic ahead of time, but in the end itís a judgement call that only you can make.

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