zerene artifacts?

[nlenoden]

I know the attached image (a pmax from about 30 Tiffs) is terrible, but
I'm hoping to make it better. I took it through my dissecting scope.
Notice all the strands of little black bubbles. I get these a lot.
They are not visible on the constituent Tiff files, so I suppose they are
artifacts from Zerene stacker. Does no one get these but me? Is there
anything I can do about them? Thanks in advance for your help.

[Scarodactyl]

Those are spots on your sensor or relay optics. Normally these would just be in one spot and not be so noticeable, but with a stereo microscope the image shifts laterally as you focus, so when all the photos are aligned you get a nice little line of spots (this also happens on a non-stereo if the subject is not totally stationary relative to the lens).
Zerene does allow you to take a dust map to automatically edit those out. Helicon does too, but it's just 'ok' not amazing, zerene's is probably better. Cleaning your sensor and relay optics is better though if possible.

[rjlittlefield]

Adding to Scarodactyl's explanation...

The case here is especially interesting because of the "zoomburst" effect with all the dust trails oriented toward a single point not far off the right side of the image.

This pattern indicates that in addition to correcting for image shift, Zerene Stacker also had to adjust scale by quite a bit to compensate for perspective foreshortening caused by the scope's entrance pupil being close to the subject.

As a practical matter, the significance of foreshortening is that different depths in your subject are rendered at different magnifications in the stacked output. Any scale bar or other measurement will be accurate at only one depth, typically the bottom of the stack. If you need to make accurate measurements from the images, you should go back to the original source images to do that.

If you do want to use a dust mask, the best way to build that would be to shoot a blank gray field (no subject) and build the mask from that. Bear in mind that if the scope has variable magnification, the dust spots may change location with scale, so check to be sure.

More information about the dust mask feature can be read at https://www.photomacrography.net/forum/ ... hp?t=41343 .

--Rik