Re: [Leica] focus inaccuracies: my test results

["Dante A. Stella" <dante@umich.edu>]

Dan, if both RFs are decoupling, get the focus stops on the lens fixed at
0.7m.  That's what the spec is.

I am endlessly amused by this thread, but I think we should all take stock of
the following:

(1)     The argument that if a body doesn't couple to a lens at the closest
distance a lens will turn to, we should replace it with another M6 is silly.
If you read Dan's post, it said that BOTH cameras (M6 and Hexar) decoupled at
the closest distance the lens RING would go to.  It is also a silly argument
because even Leica M3s are only designed to go to 1.0 meters close distance.
Should we get rid of those and get M6s?  Ridiculous.  Even modified, M3s do not
follow my 35 Summicron to the close stop.  If Leica is shipping bodies that
don't go all the way with the lenses, they should start setting the focus stops
differently at the factory.  NONE of Leica's lenses is shown in its catalog as
having a close distance of less than 0.7 meters.  All of the lenses should be
set to stop there.  This is not a quality issue - it's a design issue.

(2)     It is also unrealistic to expect that any rangefinder is accurate when
you run off the near end of the coupling.  The way you deal with this is to
focus close such that the RF "catches" and then move camera-subject distance.
Anyone who has used Nikkor LTM lenses with their 1 meter minimum coupleing and
12" minimum focus should be very familiar with this issue.

(3)    While in theory, on a tripod, you can focus a telephoto lens at 2.5 feet
wide open, in real life even breathing (yours or the subject's) will throw the
focus.

Dante


Dan Honemann wrote:

> 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