Archived posting to the Leica Users Group, 2001/08/11

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Subject: RE: [Leica] Leica M focus
From: "Frank Filippone" <red735i@earthlink.net>
Date: Sat, 11 Aug 2001 06:38:40 -0700

The traditional check requires a newspaper and a ruler.

Mount the paper at a 45 degree angle to the optical axis.  Mark HEAVILY,
using a magic marker or similar, the center of the paper.  A nice bold
vertical line.  Put ruler horizontally along the paper.  ( the ruler tells
you haw far off you are in measured terms.)

Stand back, use tripod, focus on the line, shoot picture.  Make major change
to the last focus then refocus completely again.  Do this several times.
Develop negs, inspect NEGS ( or chromes under a loupe), not cheapo color
prints ( too much chance the printer had HIS focus off).  ( You do get some
info from the distance you are actually from the bold line vs what the lens
says the distance to the line is... but truthfully, the best data comes from
the film itself)

You will see if the line is in sharp focus, or where the real optical focus
is set.  You can try this at different distances, but generally, 5-10 feet
should show you everything you want to know.

Next..... do you have another lens to make comparisons against?  The
question that arises is.. is it the lens or the camera?  Or the cheapo
printer that sold you out of focus prints?


Frank Filippone
red735i@earthlink.net