Honestly, I'm not sure yet.
I'm realizing that I use a whole different type of thinking when I copy live humans (or photos of them) than when I draw cartoon characters and I haven't yet figured out how to link the two types of reasoning.
Boy I see even more mistakes when I compare the drawings to the photos after I blog them. Like many cartoonists I tend to shrink open spaces when I copy real things. I gotta try to fix that.
I find a lot of interesting subtleties in anatomy and perspective as I copy-but will remember them after the photos are taken away? Maybe if I did this every day for years.
I had a whole bunch of theories to go with these drawings, but it's too late at night and I'm beat, so I'll have to save them for later.
I don't see realistic proportions very well. I make the feet and hands too big.
One of the reasons I've been brushing up on human drawing is because I have to design a T shirt with Marvel characters on it and I wanted to do a sort of caricatured Kirby style. I'm already running into many problems to solve.