I think composition and all that shit make the difference. It's not the same copying a professional photo than a person because if you're drawing them, then you choose the angle, the lighting, the dimensions, the frame, etc. I mean, have you noticed that the photos most people take during their vacations or at parties suck arse? That's because they don't know about composition. If a professional photographer takes a picture of the same person, it'll be completely different because he puts effort and talent into it.
For example, if Land had been given a picture of the same model buying a hot dog, even if it was a full body shot he couldn't have drawn the pin-up he did. In other words, the photographer did all the job for him.
Guys like George Perez, Brian Bolland, etc., don't need to swipe because they've studied the human anathomy and can apply it to any situation they imagine. They also know about composition and sequentual narrative, so they won't just paste a static drawing of someone in the middle of a panel, like other realist artists do. They take the human body into account when they compose the page and use it as another visual element to achieve aesthetic ballance. We don't notice this sort of thing when we're reading, but this is what makes a page by Perez a lot more enjoyable than one by Land.
