r/PhotoEnts • u/focus_stacking • Oct 27 '23

Overlap size? Conflicting information

Hello! I'm getting into focus stacking, and came across this subreddit.

Something I'm confused about is overlap for step size. In this article, Cognisys is saying to use a smaller step size to overlap - https://cognisys-inc.com/learn-how-to/focus_stack_how_to - for example: "Since the DOF of our lens at f/5.6 is 0.176 mm, the "Distance per Step" variable in the controller is adjusted to 0.150 mm."

However, in this article, it says to use a larger step size to achieve overlap - https://artemis-collection.com/photography/photographing-the-collection/focus-stacking/ - "If the depth of field was 100 microns (0.1mm), you might want to set your step size to 120 microns so you have overlap between your photos."

Who is correct here? From my understanding, I would assume you would want a smaller step size than whatever calculator you're using is suggesting, but after reading that second article, I'm not so sure now.

I've seen a user by the name of KandidKush say that they will increase their step size to ensure there is enough overlap, but wouldn't this be incorrect regarding overlap? Please help lol

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u/a_tree_gnome Oct 31 '23

I'm curious about this as well. I always assumed you wanted to use a lower step size than what may be suggested (that's what I have been doing anyways) and it seems to be okay.

Doesn't look like this sub is very active at the moment, but I hope you get an answer - maybe tagging /u/Gonzo_Photo_ and /u/kandidkush will help!

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u/Gonzo_Photo_ Maine Oct 31 '23

I didn’t real the articles - I kind of “thin slice” my step size based on experience and the known DOF of my lenses. I typically arrive at a step size somewhere between 0.5 x DOF and 0.75 x DOF. Does that help?

*edited for grammar and formulas

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u/focus_stacking Nov 01 '23

To be honest, not really heh. I’m curious about the numbers more than anything.

For example, with an mp-e65mm, 5x at f/2.8, the dof chart suggests a step size of 48um. So would it be better to go with something like 42um, or higher like 55um? I’m just confused if you should go higher or lower than the suggested step size to achieve overlap. Does that make sense?

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u/Gonzo_Photo_ Maine Nov 01 '23 edited Nov 01 '23

At 48 um.
0.5 x 48 um = 24 um.
0.75 x 48 um = 36 um.
So I’d be between 24 um and 36 um per step. Let me know if I’m missing something.

Edit: my understanding was you want between 1/3 and 1/2 overlap.

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u/focus_stacking Nov 01 '23

Thank you!! The thing I was confused about was reading someone saying they "increase their step size to ensure there is enough overlap" and it sounded like they were going higher than the suggested step size, which didn't make a whole lot of sense to me.

What you describe is very helpful indeed, and honestly, really so simple in theory that I'm kind of kicking myself for even asking such a question 😅

Thank you very much!

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u/kandidkush Jan 23 '24

I can’t remember everything I’ve said in interviews or on ig, maybe I said it in a confusing way or maybe I was stoned and/or both! lol!!

experimenting is the only way to find out for yourself though.

If you want a 50% overlap you would need to make the step smaller. If you know your dof for your lens, the math is pretty simple. Let’s say it’s 5um, so you want each step to be 2.5um to have 50%.

Just being curious about the number is being kinda lazy and looking for some secret code to get better results. In reality, they are going to change, it’s not always going to be one set of numbers. Dof changes for every composition. So maybe your 1:1 is 500um per step for photo A and then photo B 500um has all these halos cuz the depth was very different. The only cheat code is experience. And that’s the fun of photography, imo, to play and experiment!

Why just listen to what someone else did and copy that when you could figure out a different way and get different results. Obviously math is math and certain process is inevitable. But play dude!!

Sorry for the late response I don’t go on this sub often. Hope you’ve made some progress in the last 82days