[Leica] DOF

[Robert Appleby <robert.appleby@tin.it>]

If I've understood the discussion right, John is saying that DOF is a
subjective (perceived) factor which must take print enlargement into
account. Hence MF lenses have longer focal lengths but equivalent DOF
because the negative requires less enlargement. Is that right? This is news
to me, I always thought it referred to a given amount of out-of-focusness
on the film plane, and hence MF lenses would have the same DOF as the 35mm
format lenses of the same focal length.

But it does make a sort of twisted sense.
In that case, what print enlargement do the DOF markings on the camera lens
refer to?

Maybe there are really two concepts here, film-plane DOF and print DOF? The
latter can be varied by enlarging the negative more or less, but the former
is determined solely by subject distance, focal length and aperture.

Just my idea based on reading the posts over the last couple of days.

Since I never print, the idea of print DOF had never occurred to me. I'd
always thought of it just as being film-plane determined. And so I'd also
always thought the drawback of MF was reduced DOF for a given angle of view
lens.

Tell me I've understood this business!

Rob.