My Canon 10D also has a DOF button on the body. I suppose I could use it and experiment, but when I have tried using it in the past it didn’t realy help me much (maybe I just haven’t experimented with it enough yet). And it is definitely pretty dark at f22. But this is a good tip. There are so many buttons and functions on these cameras, (and more than one way to skin a cat at times) that it is really tough to remember all the capabilities and functions, especialy for a guy who just likes to keep it simple. But, I am learning more each day, and becoming even more familiar with my camera. I really want to learn the camera well, so that I can visualize what I want to do, quickly make the correct adjustments and settings, and make the shot. Like a race car driver, the better I know my machine, the faster and more skilled my driving will be. Hopefully, the more inticacies and functions on my camera I know, the better a photographer I will be.
It’s extremely hard to see.. when it stops down.. especially when you have been looking at what is proably a well lit bright image.. then you stop down and look through the lens at f22, your eye simply can’t compensate to show the DOF..