Archived posting to the Leica Users Group, 2010/02/23

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Subject: [Leica] how to test focus
From: shino at panix.com (Rei Shinozuka)
Date: Tue, 23 Feb 2010 19:04:59 -0500
References: <alpine.BSF.2.00.1002231702270.82755@shell2.crowhost.com>

i put the camera on a tripod all the legs folded in, so that it's only 
about 18 inches off the floor.  i lay down a tape measure starting from 
the column.  i then focus at a point about 5 ft on the measure.  i often 
one of my son's legos on the point i want to focus as well as a foot in 
front and behind.  i put a card with the lens identifier written on it.  
take the picture.  rack the lens all the way in and out, refocus, take 
again and once more.  then try 12 ft. 

you'll get masterpeices of conposition such as:
http://gallery.leica-users.org/v/shino/techie/L8662791.JPG.html

but you'll have an idea of where the lens is focusing.  and by taking at 
least 3 images, you'll see if there's variation due to your own eyes.  i 
used to do this with film, shoot a roll of pan-f 3-4 lenses 2 distances, 
3 shots each, run to the darkroom, develop them and look at the 
negatives in a loupe. same procedure with digital, just the turnaround 
is faster.

i've never tried to adjust the rangefinder myself, just sent them down 
to leica NJ.  i think every one of my rangefinders has been to leica for 
a rangefinder touch up, and i once had a 90mm cron which needed its own 
focus adjusted. 

-rei


Ken wrote:
> Are there any methods of testing the focus accuracy of the rangefinger 
> in a M7 vs. body + lense itself?
>
> I've though of making a ground glass that just sits on the film plane 
> and comparing using a loupe to the finder, but this is a last resort.
>
> Also, if something is off, are adjustments made to the body, the lense 
> in question or both?
>
> _______________________________________________
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In reply to: Message from kkanno at users.symmetric.net (Ken) ([Leica] how to test focus)