In much of this blog, I'm going to address you as if you were a working painter. I'm writing with the non-painter in mind as well, but many of the practical problems and theoretical issues that arise relate directly to decisions a painter makes while painting. I'm hoping this winds up being interesting for the non-painter as well, but, being a painter myself, I am in no position to judge. Incidentally, the best book I've ever read about the process and mindset of painting was written by, to my knowledge, a non-painter: Rudyard Kipling. The book is The Light That Failed. So there you go.
Anyhow, during my long day of making pictures yesterday, I painted Piera's right hand. Here it is, with a reference photograph of the hand for comparison:
Wow, those look pretty different, don't they! Yup. They do. You've seen a few of my paintings by now, so you can decide for yourself whether you like how I paint people. That painted hand is at about the level of detail and polish on most of the paintings you've seen, if you look closely enough. Compared with the photograph, the hand looks so simple and crude! But in the painting, it works (in my humble opinion).
This brings the question of detail to the foreground. How much detail is enough? You have to decide based on the aesthetics of your painting. Never be intimidated by the painters who are painting individual highlights and shadows on the wrinkles around the eyes, or individual strands of hair. What they're doing is no more "real" than what you're doing. That photograph of Piera's hand is not more real than the painting.
The level of real detail is infinite. I've seen some paintings of hands that go to the level of the individual ridges and valleys that form the fingerprints and palm prints. That's very nice. But if you actually look closely enough at those ridges, you'll see that they have a transverse hatching. If you look even closer, you can see flakes of dead skin and dust in the valleys. If you want to look even more closely, with a magnifying glass, you will see the translucence and shadows inside the skin of each ridge, and if you want to get a microscope, you can just make out cells.
There is no way to paint all this. A large part of the aesthetic question of painting is to decide what to leave out. Like so many aesthetic questions, it has a cognitive component: what is the natural cognition of detail? Your aesthetic decision pegs you relative to this population-wide cognitive mean (obviously, there is a good deal of variation from individual to individual). I favor a level of detail around the casual-glance level of cognition. This is in the Velazquez/mid-career-Titian range. Sometimes I'll go higher, sometimes lower. All the heroes of the Venetian Renaissance have a fairly low level of average detail. The fussy Germans go pretty high on the detail scale.
When I say there is no "real" depiction, because the real has no limit, I am also saying there is no "right" depiction, because "right" is an undecidable question relative to the unlimited detail of the world. Art has lots of things known to work, but it has no rules. Any rule proposed will be broken by the next genius to come along. So rely on what's known to work, if you want. Or innovate some new way to make something work. If you are a low detail painter, you are not wrong, and if you are a high-detail painter, you are not right. Be neither ashamed nor judgmental. Ask only, "Is this working?"