Re: [Leica] Simple Question

[Martin <howard.390@osu.edu>]

Arthur Leyenberger wrote:
> 
> I bought a 25mm SKOPAR this week (and LTM to bayonet
> adapter) to use on my M3. 

Congratulations!  I got mine yesterday, it's sitting on my II today ;)

> I plan to test it this weekend, but my question is that I need to use
> hyperfocal distance since the lens does not engage the
> focusing images (sorry for the non-technical names for
> these things). Should this be?

The lens has click-stops at 1, 1.5 and 3 meters.  Along with the depth-
of-field scale on the lens barrel, you should be able to see the following:

  1.5m and f/16: dof from 0.75m to infinity
     3m and f/8: dof from 1.3m to infinity
    3m and f/11: dof from 1.2m to infinity
    3m and f/16: dof from 0.9m to infinity

I have the exact figures in the little Japanese manual that came with
the lens, but that's at home.  I can mail them on Monday.  That table
has the dof values for 0.7m, 1m, 1.5m, 3m and infinity for all aperture
values.

> 1) Are there different adapters for different focal
> lengths in the M mount?

Yes.  There are three different ones, but all they do is determine which
framelines are shown.  For the M2, they are 35mm, 50mm and 90mm.  On the
M3, the 35mm will bring up the 135mm frameline.  On the M4, M4-2, M4-P
and M6, they will bring up the combined framelines.

Consequently, the SM-to-M adapters have nothing to do with focussing, only
to do with (1) allowing you to mount the lens on the camera and
(2) determining which framelines you will see in the VF.

With the 25mm Skopar, it doesn't couple to the rangefinder in any case,
so it doesn't matter which SM-to-M adapter you get.  They will all work.
Use the dof scale and the separate VF to shoot.

If you're shooting in low light and need to use a larger aperture than
f/8, you'll have to guesstimate the distance to your target and set the
lens to that distance, using the distance scale on the lens barrel.  It's
not difficult.  Practice with a rangefinder coupled lens and the camera.
Look at an object some distance away from you. Estimate the distance, and
set the lens to that, WITHOUT looking through the VF, only looking at the
lens barrel.

Then, look through the RF at the object without changing the focussing on
the lens.  You'll see how close or how far off you were.  Practice on
different objects at distances from 1m to 20m.  You should get very close
with only a little practice.

I spend about 8 hours over one weekend doing this, and got to within a
couple of centimeters consistently with a 50mm lens.


> 2) If I buy the 15MM Heliar will I have the same
> problem? I realize that at 15mm, almost the whole
> world will be in focus.

Yep.  Just point and shoot.  Stick the lens at 1m and f/8 and everything
you can see is in focus in the shot.

> 3) If I were to buy and use Leica SM lenses, would
> they to have to be focused hyperfocally (sp?)?

Again, you use the depth-of-field (dof) scale on the lens barrel.  I
typically use the markings for the next larger aperture (except on the
Skopar).  So, if I was using f/8 and wanted to make absolutely sure that
things were in focus, I'd use the dof markings for f/5.6 on the lens
barrel.  That way, I have the margins on my side.

Good luck!

M.

- -- 
Martin Howard                     | 
Visiting Scholar, CSEL, OSU       |    What boots up must come down.
email: howard.390@osu.edu         | 
www: http://mvhoward.i.am/        +---------------------------------------