Quote Originally Posted by Lee L View Post
Sorry Lee, you are wrong on this. When I first started working at Kodak and I was studying optics, I asked this question based on experience. One of the optical engineers sat down with me and Smith's book on optics and started with two equation. Substituting one into the other, with in two lines, the focal length drops out of the equation. I wish I had taken notes on it, but the bottom line is that for the same image size [magnification] the focal length is not a variable and the theoretical depth of field is the same for all lenses.

Search my posts, I have covered this in great detail in the past.