That is because if you take many photographs and you do it conscientiously, alot of your decision-making becomes instinctive, or second-nature, but it is still based on photographic principles that have both artistic and scientific foundations. Hence, your work is the combined result of art and science. And if you were painting pictures it would be the same in principle, but with a different set of creative constraints and possibilities influenced by the medium. I find all of this so obvious that the discussion is kind of pointless - unless I'm missing something?
You may be missing something. People who think that a creative form like photography or painting involves science (and some famous artists, like Seurat, actually thought that) tend to be unable to either see past the structure of the technology they're using, OR they make fruitless attempts to achieve art by doing what scientists to, which is to reduce a problem to its most basic elements, and then rebuild from there. Art doesn't seem to work like that.
I'm now going to make a generalization which will annoy some people, and to which I am sure there are exceptions -- and that is, people who take scientific and engineering approaches to art generally fail. Engineers in particular seem to be drawn to photography, perhaps because of the aparatus involves a lot of technically interesting aspects (optics, materials, timers, chemistry, etc.) and yet may produce art. Still generalizing, I find that there are a lot of engineers who make photographs of extreme competence, but of little interest, because they tend to focus on the reductive -- the most perfect exposure, the best edge sharpness, the greatest dynamic range. This leads to preoccupation with subjects like aspen trees, water leaping over rocks, slot canyons, and so on, which really demonstrate the technology, but when you look at it...well, who really gives a sh*t? You've already seen 10,000 photogaphs like that in your life, why do you want to look at another one?
The application of technology doesn't lead to art, it leads to repeatability. Good art tends to be unique, each and every time, and is unrepeatable. If you sent Ansel Adams back to Herndanez New Mexico to shoot moonrises a hundred different times, chances are he'd never exceed the results he got the first time.
What you're missing here is that ART doesn't involve science except in the most useless sense; so if you want to make art, approaching it from a scientific point of view is essentially useless. The Briot essays would be better off discussing methods for achieving a personal vision...
Jonathon tends to throw around words like ridiculous, which no longer bothers me, because I've been a forum member for a while, and value his other insights, but frankly, saying that photography involves science is about like saying riding a bicycle involves science. Bike riding may illustrate a lot of scientific principles, and make use of a lot of technology, but getting up the mountain first ain't science.