question about chromatic aberrations (and 2 filters in photoshop)

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bbobby
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question about chromatic aberrations (and 2 filters in photoshop)

Post by bbobby »

Today I was examining the images from Canon 180mm f/3.5 L Macro USM.
I read a reviewer wrote (some time ago and without any pictures)
"There are no lateral color fringes, even without a lens profile on full frame."
My images - this example is 100% crop of 4 black dots (0.5 mm diameter) from the center (no CA), then from the left upper corner of crop sensor (or about middle frame of the full sensor) and the last is the left upper corner of the full frame - shows clearly visible purple and green/cyan aberrations away from the center.
I was looking for some way to see them more clearly and defined and at the end I applied "trace contour" and "find edges" in Photoshop. Also tried the channels... Anybody knows better way to isolate and emphasizes them?
I think somebody mentioned somewhere that if pictures are taken with different light (only red, then green, and then blue) these CA can be measured or something like that?
chromatic aberations.jpg
mag and blk.jpg
Last edited by bbobby on Tue Feb 14, 2023 5:36 pm, edited 1 time in total.

ray_parkhurst
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Re: question about chromatic aberrations (and 2 filters in photoshop)

Post by ray_parkhurst »

Very interesting. What was the target?

Also, what are the differences between the various groups of images...left to right...top to bottom?

bbobby
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Joined: Sat Jan 15, 2022 12:40 pm
Location: Indianapolis, IN

Re: question about chromatic aberrations (and 2 filters in photoshop)

Post by bbobby »

ray_parkhurst wrote:
Tue Feb 14, 2023 5:36 pm
Very interesting. What was the target?

Also, what are the differences between the various groups of images...left to right...top to bottom?
I am sorry I was just adding that in my previous post... Max Levy Autograph FA 111 - 0.50 mm dots. I was checking to see if there is distortion (there is some), but I think it is perfect way to see CA too. This image is at f/8 - f/3.5 would be way worse. 4 dots from center of the frame (right image), then from where the upper left corner of crop sensor should be and the left image is from the upper left corner of full frame (5DS R).
Untitled-1.jpg
And I just remembered that Lab could be useful - and sure it is...
lab.jpg

blekenbleu
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Re: question about chromatic aberrations (and 2 filters in photoshop)

Post by blekenbleu »

bbobby wrote:
Tue Feb 14, 2023 5:26 pm
I think somebody mentioned somewhere that if pictures are taken with different light (only red, then green, and then blue) these CA can be measured or something like that?
I measured a target with separate red, green and blue LEDs for focal distance differences AKA longitudinal CA:
https://blekenbleu.github.io/microscope/#CAL

Your evaluation is more about magnification differences AKA lateral CA.
Metaphot, Optiphot 1, 66; AO 10, 120, and EPIStar 2571
https://blekenbleu.github.io/microscope

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