[Leica] Focusing on a plane

[shino@ubspainewebber.com]

sometimes, i take a photograph using the rangefinder like a spot focus
meter.  for example, using the diagram below, i might take a photo where
C is at the center, but i am focusing on R.  

(use constant width font)

      --------C'-------
      -L------C------R-
        \     |     /
         \    |    /
          \   |   /
           \  |  /
            \ | /
             \|/
              M6

with a rangefinder, i might focus on R by pointing the camera to R using
the rangefinder, and then recompose, so that C is again at the center.

but now, i was thinking, isn't the distance RM6 greater than CM6?
and therefore, the plane of focus be behind R, such as the plane passing
through C'?

i suppose this would only be an issue with wider angle lenses.

- -rei

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