On 9/26/2014 7:06 AM, Chuck Norcutt wrote:
Ever since I read Mike Hattem's tests of adapters you've described
below I can't figure out what he was carrying on about. Consider that
the front and back mounts are not perfectly parallel. How is that
different from tilting a lens with a tilt/shift adapter? And if it
was a truly bad machining job... maybe only by 0.001-0.002 inch. The
image is not "distorted", only the plane of focus has changed. Unless
he's testing using a perfectly flat object located very close to the
lens and with almost no depth of field and also very precisely
parallel with the image plane I don't see how he could detect it...
even at 100%. I don't see that such a small error in the parallelism
of the two mounting faces is any kind of real world problem.
What's wrong with my logic?
Nothing at all, it's the same as mine, which found his assertions
unlikely at best. Except for the usual problem with theory - empirical
evidence. It's been a long time, but I recall seeing a difference in the
images he provided.
I don't now recall if the issue was parallelism, length, ??, but the
same logic applies. And yet he had careful test images showing a
difference between adapters. Absent another theory, one is forced to
consider that very fine machining differences may matter. The
differences were minor, and only visible in A-B comparisons at 100%, but
certainly there.
Parallel Puzzle Moose