I had a brain cell fizzle on me tonight, and a question popped into my head. Say I have a subject that is a given size. Say, a loaf of bread. And I want to fill the frame with this loaf of bread, regardless of the focal length of the lens I use. Assume I have a really big kitchen and could use anything from 17mm through 500mm to photograph this subject. So, I would set the tripod down at different distances from the subject to accomplish this. At 17mm, I would be right there. At 500, way over at the breakfast nook in the far corner. Now let's say I want to sell this loaf of bread on eBay, and I want a shot of it where the entire loaf is within the DOF so that bidders can read the label, check for mold, etc. Does it matter what focal length I shoot the loaf at, in order to achieve the DOF I want, or is the aperture the only thing that matters?