Stacking Gremlins

[dancingcat]

I was studying stacking artifacts the other day, trying to understand halos appearing around petals of flowers (high contrast against dark background). I’d been seeing a lot of this in my Olympus in-camera visible stacks, so was puzzled.  Soft halo looks like this around the petals..

 

I found a good description of the most common stacking gremlins here by Allan Walls Photography.  He’s a macro photographer, and uses big stacks processed in Zerene.

It’s a long video, but I found it well worth watching; here’s a summary from my notes.

 

1.  Wiggly Worm - wormy things in the background.  Caused by dust on the sensor.

2.  Background Banding - caused by changes in lighting between stack shots, common with flash.  Minimized by using continuous lighting, or in Pshop blur the entire background.

3.  Ghosting - caused by motion in the background ie clouds, water, grass.  Run an extra pass in Zerene using higher settings and retouch.

4.  Echo - caused by motion in the foreground.  Remove the frames with echoes from the stack, or reshoot.

5.  Halos - soft halos are caused by stacking software becoming slightly confused trying to smooth areas with high contrast, worse with light subject on black backgrounds.    Big blurry halos can be caused by variations in light source; psychedelic halos bleeding into the background can be caused by lighting or shots in the stack being in the wrong order.  Tight, hard halos with chunks are sometimes found in dmap stacks - increase estimation radius and rerun.  Generally stacking with pmax will overcome soft and color bleed halos.

I found the Zerene help page very useful - for the differences in pmax vs. dmap stacking and how to retouch using one or the other or individual stack images.

 

For Oly shooters, my conclusions after a little bit of study is that the halos are not a function of the camera or the lens, they are a function of the in-camera stacking software, and maybe the lighting.  So I will probably forgo the Olympus in-camera stacking (turn focus stacking off), and just do individual shots (turn focus bracketing on and start focus on closest part of the subject) and do all my stacking in Zerene.  I think Oly's in-camera stacking works ok most of the time, but simple bracketing and export to better stacking software seems to be the right plan for my flowers against a black background.   The new OMDS OM-1 camera seems to treat focus stacking/bracketing the same as the EM-1 series does.  I haven't done many in-camera stacks in the ultraviolet because of the longish shutter speeds, but have not seen soft halos in those images.

 

[Andy Perrin]

Yeah, I’m not surprised that is the conclusion. You get so much more control on the computer. 

[Yves W]

I had this halo problem with Combine Z over 10 years ago. Since Helicon Focus and these different methods, I no longer have this problem. In photomicrography, I make stacks of more than 100 photos and even 200.

[Andrea B.]

Nice notes about stacking artifacts - thanks!!

 

Question: When you set the Oly to stacking mode, does it save the series which makes up the final stacked single image? If the in-camera stacking worked, you're done, else you can use the saved series in Zerene. 

 

None of the Olympus stacking artifacts compare in badness to the mess that my S1R made of a close-up stack. The S1R seems to do better with non-close subjects. 

[dabateman]

@Andrea B.,

Yes with Olympus cameras in focus stacking mode you get both the final result and the single images used for the stack. Which includes raw images if set to record jpeg plus raws. But the final merge is only a jpeg.

 

[Andrea B.]

Thanks for the answer. I'm looking casually at KEH for used Olympus bodies to perhaps try.

 

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Final merge in S1R is also JPG.

 

*****

 

Here are two PDF stacking books. Both by Michael Erlewine and offered free on one of his websites.

The Art of Focus Stacking:  A Primer. Covers a wide range of topics around stacking.

ArtofFocuStacking.pdf

 

The Art of Focus Stacking: Book Two. The 2nd book is photos only, not tutorial.

AOFS_Workbook.pdf

 

Added later: These PDFs will only be available if you are logged in.

[JCDowdy]

55 minutes ago, Andrea B. said:

Thanks for the answer. I'm looking casually at KEH for used Olympus bodies to perhaps try.

 

I recently acquired a used Panasonic GX85 to start experimenting with focus bracketing.