Quote Originally Posted by tkamiya View Post
I've been at this for two nights now and results aren't good. I got it down to:

2cnuf^2(u-f)
---------------------------
{f^2-cn(u-f)}{f^2+cn(u-f)}

I see a common term "cn(u-f)" but can't do anything from here...

So much for wanting a simple explanation!

In my opinion, thinking about DoF in terms of magnification is not any simpler than thinking about it in terms of distance and focal length, but in case the subject magnification is already known or calculated, the equation to determine the depth of field (dF) simplifies to (see attached), where c is the circle of confusion, N is the lens aperture in f/stops, and m is the subject magnification. This equation is adequately accurate for subject magnifications larger than 0.1, which means it can be used for close-up but not landscape photography.