Re: [Leica] M-focus procedure

[Jim Brick <jim@brick.org>]

Simon,

I personally would never use DOF tables for portraits, full length or
otherwise. Focus on *the* subject. But not very far back on the subject.
Assuming the person is looking at you, don't focus on the ears. In any
portrait, animal or person, the eyes *must* be critically sharp. My saying
focus slightly in front of the exact subject point is assuming you want the
DOF to cover more equally front to back. Not 1/3 - 2/3. More true for
landscapes, urbanscapes, etc. When focusing on people, animals, or other
non-scape type subjects, focus on the subject, but not back too far.

In all cases, you yourself have to determine exactly what it is you want in
focus, and how much of it you want in focus. The tools available will allow
you to do this without guesswork. Do it long enough and it becomes intuitive.

DOF tables are based on the acceptable Circle Of Confusion. If I need to
check a DOF table and I know that I might want a *big* print, I use the
table as if I were using an f/stop *two stops wider* than I'm actually
using. This will guarantee critical sharpness in the specified area. Lens
set at f/16, read the DOF table for f/8, for guaranteed critical sharpness.

Of course, when using an M camera, your lens/RF adjustment must be in spec.
It's not like the ground glass screen of an R camera, where if you see it
sharp, it is sharp.

Jim


At 02:38 PM 7/6/98 +0100, you wrote:
>Jim, thanks for the post on focusing and depth-of-field - it
>got me thinking...
>
>If I rely on the DOF and focus a full-length portrait slightly
>in front of the subject, won't I get a plane of focus in front
>of the person that is sharper than the subject, and if there
>happens to be something in the shot at that distance like a
>piece of furniture, or some grass or plants, they'll be sharper
>than the subject won't they?  DOF is only defined for a
>specific enlargement factor and a specific viewing distance
>(circle of confusion), right?  So if I enlarge the resulting neg
>more than the guy who printed the DOF tables expected me
>to, the print will actually not necessarily be "in focus" where
>I want it to be?  I guess we have to decide what size we want
>to enlarge the picture to before we shoot it...
>
>Simon.
>