[Leica] focus inaccuracies: my test results

["Dan Honemann" <danh@selectsa.com>]

Well, I've been playing Erwin all week, taking roll after roll of test shots
with my new 35/1.4 asph and 75/1.4, and my trusty 50/2 on both .72x M6 TTL
and Hexar RF bodies.  The results have me perplexed as to how to proceed
from here.

First of all, the 75: it focuses accurately on both bodies down to the last
printed distance marked on the lens, 2.5 feet.  The problems crop up
somewhere beyond that point--as the focus ring on the lens turns a full inch
or more yet closer.  Turning it as far as it will go clockwise results in
consistently mis-focused shots on both camera bodies: the point of focus is
about 1-2 inches (2-3 inches on the slides, but the ruler is at roughly a 45
degree angle) closer than the target (the area in which the RF perceived
focus).  The shots at infinity look good from what I can tell, but it's hard
for me to judge focus of a TV station antenna some 10 miles away.

Since the 75 is dead-on accurate at a distance of 2.5 feet (and also tested
fine at 1 meter), I worry that if I have the lens calibrated to get the
closest focus right, it will throw off the focus for the rest of the range.
If I have the body calibrated, same problem--and the M6 focuses the 35 and
50 fine all the way to their closest focus.  The other options would be to
have Leica (or DAG) "fix" the focus ring so it will not turn any closer than
2.5 feet, or else stop to check what distance I'm at on the lens every time
I'm focusing up close and move it to 2.5 feet if it strays beyond that
(yuck).

While the 35 and 50 focus accurately all the way down on the M6, they quit
engaging the rangefinder on the Hexar after .7 meters (or thereabouts) and
consistently focus too close by at least an inch on that body when the rings
are cranked all the way clockwise.  For the 35, it's even worse: it
mis-focuses by 1/4 to 1/2 inch too close even at 1 meter.

I get the infinity test results back on the Hexar tonight, but I'll be very
surprised if they aren't accurate (and it will be impossible for me to judge
if they are only a bit off, anyway).  The real problem seems to be that the
focus rings on the lenses all turn beyond the point at which the rangefinder
on the Hexar is engaged, and so there's no hope of being able to focus these
lenses accurately at this point unless the RF can be adjusted to support
their full range.  The fact that the 35 doesn't focus accurately at 1 meter
is more disturbing, as the rangefinder is definitely engaged at that point
(and this is the lens I planned on using fulltime on the Hexar); all of my
shots, however, show that it focuses at least an inch closer than the
target--which the M6 manages to focus on just fine.

Ok, fellow Konica owners, do you find your Hexar RF's do the same thing as
mine?  If so, and if you shoot wide-open and up-close as often as I do, is
it any wonder your slides are coming back soft?

And all you 75 fanatics: maybe the reason why your head shots are so hit or
miss is because the focus ring on the lens goes too far--by at least an inch
beyond the minimum focus distance for which the lens is specified.  I'd be
very interested in hearing if other 75 owners have found that the lens is
accurate to about 30 inches, but focuses too close for the rangefinder when
the subject-film distance is less than that (and if you haven't tested this,
you might want to try it).

Dan