Some years back, some of you may remember, I threw some m50/1.4 against a brick
wall (tested). I used a tape measure and focused via the scale on the lens. I
did that because at f/1.4 the narrow depth of focus exacerbates any errors in
the mirror-groundglass v. lens to film paths. In those tests the ME Super I was
using focused pretty close, but not exactly at about 8 feet (off enough to
affect sharpness at f/1.4 but not at f/2.0 if I remember correctly).
The interesting thing was one lens, the one I was unhappy with, would not get a
sharp slide @ f/1.4 no matter how you focused it. Not exactly true because I
found with some experimenting that it focused at about a 15 degree angle (that
is by turning the tripod mounted camera about 15 degrees to the left the wall
came into focus). However all the lenses focused normally from f/2.0 down. I
still do not understand how that was possible, but kind of suspect it was
caused be an element being slightly cocked in its mount.
Of the other two m50/1.4 one was OK, and one was very sharp (all three were
acceptable from f/2.0 down). So it seems there is quite abit of variation in
M50/1.4 lenses (none of these showed any sign of damage). However, as I have
mentioned before, these lenses are mostly 25+ years old and we have no idea
what they have been through.
I found less sample to sample variation in the m50/1.7 lenses. The one I kept however was super sharp at f/1.7 even at close focus distances.
graywolf
http://www.graywolfphoto.com
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