Chromatic aberration?

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MacroB
Posts: 92
Joined: Mon Nov 15, 2010 2:26 pm

Chromatic aberration?

Post by MacroB »

Greetings all!

Is this chromatic aberration on the bristles near the 3 simple eyes? And what about that brown, glazed look on the left complex eye - could that be the result of diffraction?

Taken on EOS 50D, MP-E65 + bellows + LM Scope, all in all about 14X. Stack of 48 in HeliconF, paramater B= R3. S4.

Due to closeness of the specimen to lens had to use fibre optics rather than LED reflector dome. Might the different angle of the lights have contributed to the aberration?

The second photo I did manage to use LED reflector dome and that seems reasonable.

All the Best, MicroB[img]http://www.photomacrography.net/forum/u ... s_XX_1.jpg[/img]
[img]http://www.photomacrography.net/forum/u ... _x15_1.jpg[/img]

ChrisLilley
Posts: 674
Joined: Sat May 01, 2010 6:12 am
Location: Nice, France (I'm British)

Re: Chromatic aberration?

Post by ChrisLilley »

MacroB wrote:Image
Image

rjlittlefield
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Post by rjlittlefield »

MacroB, welcome aboard!

The rainbow highlights on those bristles in photo #1 are not due to color aberration in the lens. Instead they are due to some interaction between the bristle and highly directional illumination. Beyond that, we do not understand the effect in detail. See extensive discussion and experiments in the thread HERE.

I'm not sure what you mean by "brown glazed look on the left complex eye". If you mean the featureless dark brown area at upper left, that looks like an effect we've come to call "stacking mush". It is produced by certain stacking software (notably Helicon Focus) when confronted with low contrast detail. You could check by looking at the original frames. If the original frames contain recognizable detail but the stacked result does not, then you've been mushed. Other software such as Zerene Stacker's PMax method is essentially immune to mush. As to what might cause low contrast in the first place, that would be some interaction between the subject and your illumination. It almost looks like a shadow is being cast over that spot. Alternatively, perhaps the light is coming in at an angle such that nothing in that area of the eye reflects any highlights toward the camera. Both problems would be avoided by the more diffuse illumination used in your second image.

--Rik

PS. Standard disclaimer: I'm the guy who wrote Zerene Stacker. Mush was one of the reasons why. See HERE for an extreme example.

MacroB
Posts: 92
Joined: Mon Nov 15, 2010 2:26 pm

Chromatic aberration?

Post by MacroB »

Hello Rik,

Many thanks that answers all my questions. Like the expression "stacking mush", if not the actual appearance of it.

I know I will shortly have to change over to Zerene Stacker.

Greatly enjoy all the topics and posts - they are a wonderfull inspiration.

Thanks again.
Regards,
MacroB

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