+1. To make it clear, this refers to the DOF you will see in the OUTPUT, i.e. if you print to the same size paper from different negative sizes. On the film, the DOF is purely dependent on the f-stop and nothing else. One thing to also remember, though, is that lenses are not symmetrical in DOF either side of the focus plane, unless they are ideal lenses (with a P-value of 1). Some lenses are designed to give more DOF behind the focus plane than in front, and vice versa. So you have to use similar lenses for the different formats if you truly want matched DOF. My own take is that I prefer lenses with good bokeh, and do not obsess over DOF, unless it is for instance landscape photography. I just shoot my lenses where I know they perform well, and where I get the shutter speed that works for the situation.
Originally Posted by polyglot
I can't explain it better than Paul van Walree: http://toothwalker.org/optics.html. I suggest you visit his site and have a good read. The other characteristics of optics are also explained. Interesting stuff.
Last edited by dorff; 05-07-2013 at 03:16 AM. Click to view previous post history.