On 9/17/2018 9:57 AM, Jan Steinman wrote:
From: Moose <olymoose@xxxxxxxxx>
On 9/16/2018 9:48 AM, Jan Steinman wrote:
let you create lens profiles for lenses that were developed before profiles
existed, like my OM Zuiko stable.
Ah, yes, that's the one I've encountered in a few apps. One person's opinion,
after careful comparisons - LensFun is
significantly poorer than PTLens and DxO's lens profiles. PTLens is cheap and
also allows creation of new profiles. You
take the test shots, he makes the profile. Very responsive, according to Chuck
and others. There are already profiles
for most OM wides on FF, which is where I first used it. PTLens is an
independent, one man show, so should fit your
criteria. His profiles are actually slightly better than DxO for some ?4/3
lenses.
Thanks for that info. I'll look into it. When trying to get rid of CA in the OM
21/2, LensFun was the only one I came across.
In particular, fast-wide legacy glass is known for excessive CA in the corners
and edges.
As Philippe says, that's mostly not an issue with a 4/3 sensor, as the outside
zones are cropped off.
My understanding is that the CA is an artifact of a lack of "telecentricity" in
retro-focal lenses, which all SLR wides are.
Ah, looks a lot like lens CA, but actually an angle of incidence to sensor
artifact.
Whatever the cause, I see it in all the OM fast wides I've tried on a 4/3rds
sensor. (18/3.5, 21/2, 24/2, 28/2, and 35/2. Not an issue with the 55/1.2 or
longer. Haven't tried it with the 40/2 or the various 50s.)
I had been planning to use the 21/2 for astrophotography, until I discovered
the stars in the corner were purple/green streaks. That started me off on a
hunt for profiling software.
That was what caused me to sell off my fast-wides in a fit of "won't work-ism."
Having discovered focal reducers (which only came into being with Micro 4/3rds), I'm now
regretting that.
I WANT those aberrations for some of my Alt photography. They weren't there
with my OM lenses on ?4/3
Odd, that. Have you looked for point light sources in the corners? Which OM
wides were you using that didn't have CA on 4/3rds?
We were looking for different things. I was looking for BAD, and they weren't anywhere near bad enough. I didn't look at
stars in corners, and such. When not looking for BAD, I want AF, auto aperture, EXIF, and so on, so I use native lenses.
BTW, astronomer and photographer Ctein is now using a PanaLeica 12/1.4 on µ4/3 for astronomical shots, after trying
many lenses, and says it's near perfect for pinpoint star images out in the corners.
You can manually correct for that in your favourite photo editor, or create a
LensFun profile and let your open-source-based photo editor do it for you
automagically.
Well, not quite automagically, as they can't know what MF lens you used. You do
have to tell it.
True, that.
I set up my EM-1.2 to embed the appropriate manual lens info. I just wished
that it had more than ten slots for different manual lenses. With focal
reducers and teleconverters, I could easily use four times that many entries.
I have zero of those. :-)
B. A. D. Moose
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What if the Hokey Pokey *IS* what it's all about?
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