Re: [Leica] focus inaccuracies: my test results

[John Collier <jbcollier@home.com>]

Dan,

My understanding of your problem is that the 75/1.4 lens is focusing
accurately on your two M6s all the way from infinity down to 0.7 m with the
lens set to f/1.4. Anything closer results in inaccurately focused pictures.
If this is true, then the last little bit of the lens cam is not ground
properly. Hopefully it is a matter of material removal not missing material
because missing material would would mean a major repair, probably
replacement.

I have heard of the Hexar not coupling at closest focus before but whether
it is systemic or not I cannot say. Talk to Hexar and do not take no for an
answer.

John Collier


> From: "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
>