Another aspect of previsualization is envisioning just the way the tonality of the actual scene will map to the tones in the final print before tripping the shutter. Ansel Adams’ Zone System is an orderly approach to both looking at the scene with that in mind and making the pre-exposure vision a reality. In moderation, I see nothing wrong with this. The mapping will take place whether the photographer thinks about it or not, and it’s a good thing if the tone mapping fits the photographer’s intentions for the image. When tone mapping the main thing the photographer thinks about, it’s a distraction.
I wrote about an extreme example in this post:
Many years ago, a co-worker walked into my office and remarked upon the photographs hanging on the walls. We got to talking. He told me about his antique Rolleiflex, and his fascination with the Zone System. Over the years, we had many conversations about photography. I’d talk about photographs, and he’d talk about technique. One day he announced that he really had the Zone System down: he could consistently make negatives that printed on number 2 paper in 8×8 size at f/11 for 12 seconds… Over the years that I knew this person, I kept asking him to show me some of his pictures… I never saw one.
Few photographers go that far, but I’ve watched people meter everything under the sun and some things in the shade while the magic light faded to ordinary, and heard people talk about agitation for N-2 development when it was obvious that the esthetics of their pictures needed more work than their technique. In most circles today, such talk has been replaced by ETTR discussions and the like. The technology changes, but the emphasis of the susceptible remains the same.
The purpose of exposure (and negative development, if we’re talking film) is twofold: to maximize the signal the noise ratio in the final print (think of film grain as noise), and to make sure that important tones are not robbed of detail.
Modern negative films are so capable in both grain and dynamic range that, for most subject matter, you can be a little off in exposure or development and not affect the final result in any meaningful way. Modern, large sensor digital cameras have analogous capability. If you allow yourself a third or two-thirds of a stop error rather than embracing the improbably task of getting it bang on, exposure for most scenes turns from scratch-your-head-for-five-minutes hard to falling-off-a-log simple. All the time and attention you’ve gained can be put into the esthetics of the image.
If anyone is still shooting ‘chromes, forget all those comforting words; you’ve got to get the exposure right.