Friday, March 27, 2009
BY THE NUMBERS
Before digital I spent a lot of time in my darkroom often experimenting, trying different kinds of chemistry, modified techniques, something old, something new, and often learning just how limited the silver halide photographic process is. Since Photoshop and image editing I found digital photography to be pliable to an almost boundless extent. Of course the abandon you have to change the values of pixels has a different kind of limit by producing images that have no redeeming qualities what so ever. From that experience of course one should learn just because you can do something does not mean you should.
However playing with pixels can be rewarding not just in the creative exercises it affords, but also in the values of discipline and control, as well as an appreciation of the nature of the digital beast. Yet how many really understand what a digital camera really does, its just another kind of camera, right?
A generation ago when I was still doing film test reports I would photograph Kodak color targets and a Color Checker, and after the film was processed measure the results with a densitometer. That’s not done any more with digital for several reasons including the obvious. Another is culture, people today are media savvy, exposed to large volumes of images reproduced in all kinds of media and human perception is schooled in accommodating the differences between reality and its fidelity reproduced on print or screen. The other reason films tests serve no purpose, aside for the fact new films are rare these days, a digital camera is not at all like a film camera, it is really an information sensing instrument that measures what it is focused upon and records the data describing that reality in discrete numbers, red, green and blue values, for each pixel that represents the scene and provides the building blocks for its reproduction. Then when the image file saved by a dSLR is opened in Photoshop, those number values corresponding to a color value in the subject photographed are displayed in an Info window. So if you know the RGB number values of the subject, if it were a ColorChecker for instance, you have a precise basis of evaluation of the fidelity of the image to the subject. In other words your digital camera does automatically without being asked, everything I accomplished with much effort using a densitometer and tedious effort testing film in the old days.
All of the MTF curve graphs published in Kodak Film Guides are now obsolete, as well as archaic, if anyone ever did pay attention to them or understand the meaning and significance of a Modulation Transfer Function. What image quality is today consists of a learned perceptual discrimination that is a part of the culture, it doesn’t have to be measured, most people today know what to expect from the media reproduction of every aspect of reality, in fact reality today may be more a stranger than its replication in the media. A colleague and acquaintance from my old days when I enjoyed a lot of time in my darkroom had an unusual distinction, he had a signed print made by Ansel Adams framed behind glass hanging in his darkroom. It was hung in such an unusual place for a practical reason, to provide guidance of what good print quality should look like. Years ago few ever saw what good image reproduction should look like, but today it is everywhere all the time so it would be unusual if a buyer of a digital camera does not have a realistic expectation of what the camera’s output should look like.
If you have a comment, they are welcome, so please post it. If you have a question you want me to answer please address an e-mail to David B. Brooks at: firstname.lastname@example.org