"The witch doctor says he knows how to cure. There are spirits inside which are trying to get out. ... Put a snakeskin on and take quinine from the bark of a tree. The quinine works. He doesn't know he's got the wrong theory of what happens. If I'm in the tribe and I'm sick, I go to the witch doctor. He knows more about it than anyone else. But I keep trying to tell him he doesn't know what he's doing and that someday when people investigate the thing freely and get free of all his complicated ideas they'll learn much better ways of doing it."Rules such as Sunny 16 or the instinct of an experienced photographer will get them good prints, there is no doubt about that. Instinctive rules for exposure have been used since the earliest days of photography and are still used now, but the zone system of Ansel Adams allows us to talk about all the processes from exposure to the print in one coherent common language, much like how Feynman used mathematics to allow discussion of the universe we live in.
The zone system is a means to attain an end and should, and must, be modified by each individual according to their own uses and equipment. Just Ansel would calibrate each batch of film before shooting and developing. We are fortunate that digital cameras are pretty much calibrated within each brand. Therefore I would not have to drastically change my habits when I update my camera, given that I don't switch ships.
I do not print my digital images, at least not by myself. To those who do, I congratulate you on your hard earned expertise in calibrating your printers. For me, "the print" is the image I see on my crummy laptop computer monitor and that is the end product of my photography. Of course, each of you will have a different monitor with different brightness, contrast and gamma, not to mention the nonlinearity of pixels of different colours. What is pure white on my crummy monitor may reveal some detail on your ultra high dynamic range monitors and so you will see the zones differently. What matters is that as long as I keep my monitor at its current settings, the system will work for me.
So what are zones? A zone is the vocabulary used to define a shade of black. Adams concerned himself always with the final product, the print, but the concept of zones is sometimes used to describe the density of the negative as well. Since digital photography does not produce a negative, we need not worry about that.
Adams defined 11 zones for b&w prints from zone 0 to zone X covering pure white to densest black [which correspond to exposing a digital sensor indefinitely or not exposing it to any light at all]. The dynamic range or what Adams considered the "useful" range was from Zone I through Zone IX. The textural range comprising Zone II through Zone VIII was the range in which details could be discerned.
Borrowing from wikipedia, the graph below shows how Adams defined his zones.
| Zone | Description |
|---|---|
| 0 | Pure black |
| I | Near black, with slight tonality but no texture |
| II | Textured black; the darkest part of the image in which slight detail is recorded |
| III | Average dark materials and low values showing adequate texture |
| IV | Average dark foliage, dark stone, or landscape shadows |
| V | Middle gray: clear north sky; dark skin, average weathered wood |
| VI | Average Caucasian skin; light stone; shadows on snow in sunlit landscapes |
| VII | Very light skin; shadows in snow with acute side lighting |
| VIII | Lightest tone with texture: textured snow |
| IX | Slight tone without texture; glaring snow |
| X | Pure white: light sources and specular reflections |
As with negatives, additional zones can be teased out from a digital image by special processing techniques [HDR being the most dramatic demonstration of them], but to keep it simple we shall start by looking at normally processed images. Fortunately, normal processing for digital images much more trivial than normal processing of film. For this discussion, we shall consider "normally processed" as what appears on your screen if you shoot in JPEG with the standard picture style.
No comments:
Post a Comment