Re: [Leica] A most daring proposition.

[LEICAMAN56@aol.com]

Christer,

What you're seeing in the picture is the final adjustment of the rangefinder 
mechanism.  This is an essential operation to ensure proper focussing on the 
M camera.  This "big screwdriver" is actually a special tool to enable access 
to the adjustment mechanism.  The "enlarged graph" is an illuminated target 
to adjust the mechanism for its near and far ranges.  After this adjustment, 
the mechanism rarely goes out of proper adjustment.

The vertical adjustment of the rangefinder patch, on the other hand, does go 
out of adjustment rather easily, and before the M6, was easily adjusted in 
1-2 minutes.  Since the M6 and cost cutting measures by Leica, the adjustment 
now can only be made with a special tool and necessitates removing the "red 
dot."  Apparently Leica felt they could set this once at the factory, put a 
spot of shellac on the threads, and it would be maintenance free.  Wrong.  
The old, more adjustable mechanism was much better and more easily set than 
the new one.

The rangefinder mechanism in the M is an incredibly complex mechanism.  The 
M3's is the most complex with over 125 parts.  Thru cost cutting and 
simplification, the number of parts has been reduced to about 100.  This 
mechanism is composed of many diverse parts including levers, prisms, beam 
splitters, moving masks, various lenses, LED's, etc.  All must work properly 
in unison.  This optical/mechanical marvel is roughly the same size as a pack 
of chewing gum.  Every optical system needs to have the ability to be 
adjusted within specs.  It would be impossible to manufacture this mechanism 
with enough precision and not have any provision for final adjustment.  Same 
goes for lenses.  That's why "plus" and "minus" lens elements are matched to 
make up a lens system closest to specs.  And only Leica has the integrity to 
actually engrave the actual focal length of the lens on the barrel of lenses 
50 mm and longer.

Keep in mind that the only things that ensure proper focus of the lens on an 
M camera is this rangefinder mechanism and the precision of the cam on the 
back of the lens.  If any element of the mechanism is "out of spec" or is out 
of adjustment, the result is improper focus, especially with faster lenses at 
close distances.  And the hell of it is, you won't know this until you 
process the film, because you have no groundglass to check focus on as you 
would an SLR. Be grateful for the ability to make these adjustments.  The 
only cameras I know of without any provision for fine tuning are of the 
single use/disposable kind.

Bill Rosauer