[Leica] DOF and focusing

[Jim Brick <jim@brick.org>]

Just a note about my trip slides.

I've gotten through a bout 20 rolls. As I said earlier, I used the 35/1.4
ASPH most of the time. Some of the stuff could be considered happy snaps as
it involved the three ladies. Since I was using my M6 exclusively for the
last 7/8's of the trip, and since much of the stuff was not happy snaps, I
devised a focus method that seems to have worked perfectly. What I see on
the slides confirms this. And I'm using a 6x Schneider ASPH lupe.

My entire past has been using a ground glass and checking DOF visually
while stopping down. This rangefinder stuff was difficult for me. So I
started using the engraved DOF scales on the lens. I would focus on the
nearest object that I wanted to be in focus, and I took a meter reading and
figured out the exposure. I placed the foot/meter mark of the focused
object one f/stop wider than the actual f/stop that I was using. If my
exposure was 1/125 at f/8 and the closest object was 8' away, I placed the
8' mark opposite the f/5.6 mark on the DOF scale. I then looked to see
where infinity and the farther distances fell. If the infinity mark was at
say f/5.6 I moved the infinity mark to the f/8 DOF mark thus giving me a
little more leeway in the close end. I always favored the close end. After
a few days, this became very very quick. By keeping the close stuff at one
stop greater than the actual shooting aperture, crisp sharpness is
guaranteed. This is basically hyperfocal -1 focusing, with a close end
bias. It worked because nearly all of my slides are tack sharp from front
to back. In those situations that the DOF would not span the entire
distance, I figured out what was important and placed that within the DOF
scale -1 zone. I sometimes would go for hours and never actually use the
rangefinder.

This is a hellova lot faster than visually checking DOF on a ground glass
screen. I'm beginning to like my M6. Now if they could somehow make lenses
that didn't cut off part of the viewfinder image...

Jim