focus stack artifacts

Optical microscopes + digital photography
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Cancington42
Posts: 1
Joined: 21.06.2021 07:46

focus stack artifacts

Post by Cancington42 »

I was wondering if someone would be able to help me with a stack i'm currently working on. My setup is the Wemacro tube with raynox 150 reversed with a 10x plan objective. it's mounted on a focus rail and I'm using 8 micron steps. my subject is a beetle and I photographed the antennae. I took a total of 128 images.

i've tried several stacking methods and I can't seem to get a clean final image. i've attached one of the final stacked image and a couple of crops of an area that shows diffraction spikes in the final stack, but in the original raw you can clearly see that one hair is clean

the images has tons of halos and I'm not quite sure how to process this image. any advice would be really appreciated. if anyone happens to be interested in giving the stack a try, I can upload 50 some odd images to dropbox and supply the think if anyone wants to experiment with it.

thank you.

full stack:
A7V03479-B,Radius4,Smoothing4.jpg
(7.92 MiB) Not downloaded yet
crop of full stack:
A7V03479-B,Radius4,Smoothing4 copy.jpg
A7V03479-B,Radius4,Smoothing4 copy.jpg (253.77 KiB) Viewed 8407 times
crop of original raw:
A7V03479-B,Radius4,Smoothing4 org.jpg
A7V03479-B,Radius4,Smoothing4 org.jpg (469.47 KiB) Viewed 8407 times
BearThunder
Posts: 1
Joined: 07.08.2022 18:27

Re: focus stack artifacts

Post by BearThunder »

What kind of lighting and diffusion do you use? I've got more or less the same setup as you, just with the Raynox unreversed. And how is your shoot, move setup?
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Catherine
Posts: 1156
Joined: 29.04.2019 22:38

Re: focus stack artifacts

Post by Catherine »

There is significant chromatic aberration, so while the hair is clean, it's essentially de-focused. There is also significant blurring of the adjacent out of focus hairs, these two effects probably contribute to the final image. But yes, the spikes do look odd. Have you experimented with different rendering methods and parameters? Can you upload one sample focus stack that demonstrates the problem for us to try ourselves? You can upload it to our private storage.
tataharier702
Posts: 1
Joined: 04.04.2023 10:02

Re: focus stack artifacts

Post by tataharier702 »

I second this suggestion. Focus stacks can involve dozens of captures. Photoshop struggles with these even on a beefy system with 32gb of ram. Helicon handles them, and doesn't get bogged down during adjustments pikashow.fyi
ppssppgold.one
GRSM78
Posts: 1
Joined: 26.04.2023 08:20

Re: focus stack artifacts

Post by GRSM78 »

I'm having similar issues and here are my findings:
  • with a complex structures under high magnification (I shoot x5) if you do not cover the whole depth of the whole structure, Helicon cannot differentiate between an object and the background. Because the depth is so shallow at that magnification it actually sometimes confuses a blurred (out of focus) object for a part of actual object. I would think this is what happened with the hair on the top and bottom of the leg
  • For the tiny elements like hair in your mid leg part where hair almost blend into the leg and do not have much of depth I found that surprisingly smaller steps between photos do not solve that issue. However I noticed that good light that provides higher contrast helps sometime but it can still struggle with translucent elements
  • I noticed that for such a complex objects Method C seems the most reliable but stil produces artefacts
Long story short it drives me crazy sometimes, and I end up manually cleaning those in Helicon but I would love to have some sort of easier solution for those halos / artefacts
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