"Rock, Grass, Rock" 9x12, pastel - contact Michael
I take every opportunity I can to disabuse students of the notion that painting from photographs is a valuable skill. It's not. Creating a painting from a photograph is like staging a theatrical set and then trying to live in it. That impressive shelf full of books is just a trompe l'oeil; the telephone that's supposed to ring in Act II isn't wired to anything; and the roast chicken on the table is literally rubber. A painting made from a photograph is like that. At first glance, it may look right, but as you climb onto the stage and look at the props, you'll see that they're exactly that - just props.
The reason painting photographs doesn't work is that photographs contain a very limited amount of useful information. Your senses will quickly outpace the meagre amount presented. You'll end up inventing things or worse, ruining your eyes trying to decide if a particular pixel represents a flower - or just a flaw - in the photo. On the other hand, if you work from life, you can spend a lifetime looking and still not see everything. But best is this - if you have any question about your subject, the answer is out there.
So what, exactly, are the problems with photos? A lot: Values, color and perspective. Either the light areas will be blown out or the dark areas will be too murky to do you any good. You can't have it both ways, unless you're doing HDR (high dynamic range) photography. The color will be off, even if you're an expert with fine-tuning your white balance. Film (or computer screen LEDs) don't have the range or sensitivity of the human eye for color. And if you're not using the right lens, you'll almost invariably have distortion in perspective. It's not so bad for landscapes, but with architecture, the right lens can be the difference between convincing and laughable.
The only thing a photo is good for is for shape details. If you can't remember how many mullions a window has, the photograph will help you out. But if you need to know what kind of green the ocean was, you're better off looking at a color sketch you made in the field. Even a handwritten note on a pencil sketch saying "bluish-green, a little darker than the sky" is more useful than a photo - which is what the old-timers did before cameras were invented.
The above pastel was painted, of course, not from a photograph.