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Re: [OM] OM to M 4/3 adapters (MF-2 and equivalents)

Subject: Re: [OM] OM to M 4/3 adapters (MF-2 and equivalents)
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Sun, 28 Sep 2014 19:01:57 -0400
You worry enough about this stuff that you have both me and entirely Moose entirely covered. I'm retired. I have no more time left for wasting clock cycles on limbic system worry circuits... on any subject. :-)

Dr. Flash, who, unlike Dr. Focus, worries even less on this subject... assuming negative worry states are possible.



On 9/28/2014 3:37 PM, Mike Gordon via olympus wrote:
You clearly don't worry enough about this stuff.  ;-)

MFT clearly has a very thick stack but the  crop factor as you state
should help reduce any corner issues.  Then there is the matter of
veiling flare noted even very  early on in using OMZ on MFT.

http://www.biofos.com/cornucop/omz_ep1.html

Have not seen so much of that reported of late and little reports on
A7(r).  Curiously some WA  RF lenses seem to behave better on the A7
then A7r in regards to some color smearing.
Some of the adapter related WA lens issues were reported at working
apertures with Canon cams as digital film--not something one might
predict based on depth of focus considerations but perhaps
an interaction of some sort ---sl more divergent rays/stack interaction?

Anyway sufficient worry about adapting OMZ lenses cross platform will
consume clock cycles of limbic system worry circuits crowding out other
worries and improving overall happiness.  Thus my initial statement.
Perhaps if one has Drs. Focus and Flash as in house consultants, worry
about these matters becomes more difficult.

Happily worrying Mike




DAMAA Chuck writes:

I consider this all a bunch of "doesn't affect me at all".  In the first
set of tests linked below there is no mention at all of aperture.  My
conclusion is that all tests were performed wide open.  He then goes on
to say (unlike portrait photographers concerned about center
performance) that landscape photographers might notice the edge
performance degradation discovered in the test.  But how many of you
landscape photographers use f/2 or f/1.4 lenses wide open?  Certainly
not me.  Then CH Ling pointed out (using tests of Leica lenses) that
even these lenses have significant field curvature wide open.  Tilting
the lens would potentially minimize or exaggerate the curvature from
side to side... but it's still just tilting the lens by a very tiny amount.

Then we come to the second link which says:  Hey!  Wait a minute.  My
tests of last year show bad results because I didn't account for digital
filter stack thickness in the tests because we were using the optical
bench and not camera bodies.  When he inserted an appropriate clear
glass filter of the thickness the lens was designed for everything got
much better.

My conclusion from all that it that much of the problem he originally
attributed to adapters was actually due to his testing method.  It also
points out that our old OM lenses weren't designed for use with a 4mm
thick (m.4/3 size) piece of optical glass in the optical path.  But we
are only using the center of the image circle.  Perhaps some lenses
(wider ones probably) will not fare well as adapted lenses.  But
everything I've tested performs at least as well as I need it to.

My $10 m.4/3 adapters work just fine for what I want them to do.  Case
closed.

Chuck Norcutt


On 9/26/2014 6:43 PM, Mike Gordon via olympus wrote:
Parallel Puzzle Moose writes:

<<<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.

Adapting lenses can be a bit tricky to get optimum results. Why
adapter
issues withWA lenses with corner issues seems to be a predominant
complaint is not clear to me. I recall believable posted images by the
pixel peeping alt lensers on FM. Some sensors seem more subject to
corner smearing/color shifts with more divergent rays as well in
lenses
designed for different platforms. Sensor stack thickness can play a
role
in degrading expected performance as well especailly in morrorless
cams
with thick senosr stacks.
Ming Thein seems to think the adapter issue is more cricial on short
registartion mirrorless cams but I don't remember any rigorous
supporting data.
Roger at Lensrentals is really good at teasing out the issues:


http://www.lensrentals.com/blog/2013/09/there-is-no-free-lunch-episode-763-lens-adapters




http://www.lensrentals.com/blog/2014/06/the-glass-in-the-path-sensor-stacks-and-adapted-lenses



The varation in performance with adapters was much greater than
typical
sample variation with good lenses.

Adapt often but with caution, Mike



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