Problems with stacking

[angeche]

Hello, I continue the quest for the perfect bug pic. I have used a Panasonic GH2 m4/3, a Konica adapter, a Konica bellows with a 40mm Hexanon f1.8, I have inverted the lens. I have used the scale in the bellows to take the pictures in equal steps. I have used the programme CombineZM for the stacks. The bug is 5 mm by 8 mm at most.

I took 102 pictures at full aperture f 1.8. Each picture taken at half steps from the scale in the bellows. The results have been very poor:



Somehow the greater the number of pictures the poorer the results. Why? No idea, really....

I also took 45 pics at f11, taken at one step of the scale intervals. Better results indeed, although far from perfect (light on the left side was poor and thus no detail can be seen):




And a close up of the eyes:



And now both pictures after sharpening






The question is why using more pictures at full aperture does not render good results. Or, in other words, is it a question of f1.8 not being optimal or a software issue or..... Well, I need your help...
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Jose M., just learning!

[ChrisRaper]

I'm sure someone cleverer than me will be along soon but I would guess that f1.8 is sub-optimal for that lens and there is just too much out of focus for the CombineZ to make sense of it. Have you tried something in the middle - wider than f11 but smaller than f1.8?

You could always download and try Zenere Stacker and test to see whether it makes a better job of the stacking ... a chap who sometimes posts here knows all about it

[rjlittlefield]

Jose, welcome aboard!

You're running into a number of problems.

First is that indeed f/1.8 is not a good place to be running that lens. Stop it down to f/5.6 and you'll get better results.

Second is that you're probably getting quite a bit of flare from stray light bouncing around. Make yourself a macro lens hood with a cone of black paper, as shown HERE, first panel, bottom half.

That page will also illustrate the effect of changing aperture. In brief, f/1.8 is way too wide, f/11 is probably too narrow. But it depends on your lens; test to be sure.

Third is a problem we've come to call "stacking mush", where in a deep low contrast stack, the software loses track of what's in focus and ends up showing fuzzy stuff instead. That's probably a large part of why you got better results with a shorter stack.

Finally is the choice of stacking methods. I'm guessing that this was processed with CombineZ's "Do Stack" macro. That one works fine in other situations, but for what you're doing here I suspect that Do Soft Stack and/or Pyramoid Maximum Contrast would give better results.

It's a good suggestion to try Zerene Stacker (HERE), but you should get the aperture and flare problems under control first. Once you're getting good images to work with, then you can fire up Zerene Stacker using "Align & Stack All (PMax)", and move forward from there.

Looking again, I see two more issues...

One is that it looks like your camera is not quite aligned straight down the rail. That's what causes the sideways streaking that we see under the antenna on left, but not on right. What's happening is that the camera is looking a bit off to one side, so as you rack it forward, the line of sight shifts sideways on the bug.

Second is that it looks like your color balance is off, too blue. Be sure that the camera is set to match the illumination. If you're using something odd for illumination, then do a custom color balance from something neutral like a white index card.

Hope this helps!

--Rik

[angeche]

Thanks for the input. I have used Zerene stacker with better results:



I will try to improve my technique and methods as suggested. But discovering Zerene stacker is a big plus....
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Jose M., just learning!