In his biography, Ansel Adams said the following about his 1927 photograph “Monolith: the Face of Halfdome”:
“As I replaced the slide, I began to think about how the print was to appear, and if it would transmit any of the feeling of the monumental shape before me in terms of its expressive-emotional quality. I began to see in my mind’s eye the finished print I desired: the brooding cliff with a dark sky and the sharp rendition of distant, snowy Tenaya Peak. I realized that only a deep red filter would give me anything approaching the effect I felt emotionally. I had only one plate left. I attached my other filter, a Wratten #29(F), increased the exposure by the sixteen-times factor required, and released the shutter. I felt I had accomplished something, but did not realize its significance until I developed the plate that evening.
I had achieved my first true visualization!
I had been able to realize a desired image: not the way the subject appeared in reality but how it felt to me and how it must appear in the finished print.”
The digital photographer does not typically use tools like the dense #29F red filter Adams used for controlling how tones were captured on B&W sheet film. We have instead the advantages of post processing tools to render images in many ways after the fact. What we often forget is that we also have tools, like the histogram and exposure compensation when we make the original exposure, that will help to control how the information in the file is captured for use in post processing. If these tools were not important and useful, all cameras would only have auto exposure and all photographers would produce perfect images without having to make any decisions.
While some forms of photography like weddings and events require a certain amount of “reactive” ability to capture what unfolds in front of the camera, the proactive photographer still has control over important elements of the situation. Positioning the camera relative to ambient lighting, fill flash, aperture for controlling depth of field, and other choices that are part of the proactive approach of the better photographer. Even photojournalists who are the ultimate reactive shooters get the best shots because they are proactive in many respects, preparing themselves to be able to react to unfolding events in an instant, and creating images others miss.
Totally proactive photographers work in controlled environments like studio settings where small details about the positions of subject matter, and precise lighting decisions make the image exactly as the photographer wants it to be. Many kinds of photography are simply a blend of the two approaches. Even in something as seemingly unrushed as a landscape photograph, the beginning of the experience is the reactive discovery of an interesting subject, followed by the proactive process of composition, exposure decisions, modifications of angle of view and visualizing the result.
As you move around a subject, change zoom settings and such you are initially being reactive to what appears in your viewing screen. Improving your images comes from being proactive in analyzing the details of composition, inclusion or exclusion of subject matter, fine tuning exposure and finally deciding that it is time to “release the shutter”.