Archived posting to the Leica Users Group, 1998/07/08

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Subject: [Leica] same exposures???
From: Francesco Sanfilippo <fls@5senses.com>
Date: Wed, 08 Jul 1998 15:45:54 -0700

I recently ran an informal test on some film I was trying for the first time
(Sensia II).  I rated the film at different aperture/shutter combos, always
at the same exposure.  For example, if the exposure from my incident
meter was 1/250 @ f/8, I would also try 1/500 @ f/5.6, 1/1000 @ f/4,
and 1/125 @ f/11.  This was on my M6, by the way.

I found that as the apertures got smaller (towards f/16), the slides were 
slightly darker, and as the aperture enlarged the slides were slightly 
lighter.  I have noticed this before, but didn't think much of it since the
decrease or increase of light is only 1/4-1/3 stop per f-stop.  
Shouldn't a slide exposed at 1/250 @ f/8 look EXACTLY like a slide
exposed at 1/60 @ f/16 or 1/1000 @ f/4 ??  I thought the only thing
that would change would be motion-freezing ability (the shutter speed)
and DOF (the aperture).  Does this signify a probem with my M6, or is
this a phenomenon well-known by everyone but me?

Francesco