Re: [Leica] how can the 75 Lux focus go bad?

[Gilbert Plantinga <gilplant@earthlink.net>]

I would add that it would be a good idea to also test the lens/body
combination at infinity - shoot something at least 3 miles away. My 75 went
to Sherry when I found out that it was actually off at all distances. I'll
report back when she's done with it.

Gilbert

> From: "Dan Honemann" <ddh@home.com>
> Reply-To: leica-users@mejac.palo-alto.ca.us
> Date: Wed, 7 Feb 2001 11:16:55 -0500
> To: <leica-users@mejac.palo-alto.ca.us>
> Subject: RE: [Leica] how can the 75 Lux focus go bad?
> 
>> How exactly does one objectively check a new 75mm Summi to see if it has
>> focus problems?  Thanks,  Steve
> 
> Tape some newsprint to a notebook or binder and tape a ruler on top of that.
> Then open the notebook to an angle of at least 30 degrees (enough that you
> will be able to focus on the 6" mark of the ruler, but not so much that it
> is virtually parallel to the film plane, as you want the front and far ends
> of the ruler to have some measureable distance from each other).
> 
> Using slide film, tripod and cable release, try this sequence of tests (best
> to do this with multiple bodies and lenses, if you have access to them):
> 
> (1) position the camera's film plan at precisely 1 meter from the subject
> (6" mark on the ruler) and the lens set to the "1" meter distance mark,
> without focusing at all, then shoot;
> 
> (2) leave the camera/tripod at the same postion (1 meter) and focus the lens
> so that the RF lines up perfectly on the 6" mark, note the precise location
> on the lens barrel (hopefully it will still be on the 1 meter), and take a
> shot;
> 
> (3) return the lens barrel to exactly the 1 meter mark and move the tripod
> forward and backward until the rangefinder shows focus on the 6" ruler mark
> (hopefully, it will be the same spot), measure and record the new distance,
> and take a shot.
> 
> If all three measurements line up and all three shots are in focus,
> everything is right and well.  If some of the shots are in focus while the
> others aren't, then these tests should tell you whether the problem is a
> result of just the lens being off or just the rangefinder (if it is both,
> then all three shots will be out of focus).
> 
> Just one way,
> Dan
> 
>