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what is focus stacking?

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dCap View Drop Down
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Post Options Post Options   Quote dCap Quote  Post ReplyReply Direct Link To This Post Topic: what is focus stacking?
    Posted: 18 January 2021 at 17:49
I've seen mention of this in a few threads the last couple of weeks. And I've heard of it - some form of macro magic - but I'd like to know what and why it really is a thing.

A couple of the shots I've seen look perfectly achievable with normal macro shooting ... I thought it was mainly used in super ultra high reproduction stuff (e.g. insect eyes).

Can someone smart explain please.
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Post Options Post Options   Quote Hezu Quote  Post ReplyReply Direct Link To This Post Posted: 18 January 2021 at 18:33
You first take a series of (macro) photos where in each the focus is in a different spot and then you use post-processing software to merge these into one picture where whole picture is sharp.
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Post Options Post Options   Quote Wētāpunga Quote  Post ReplyReply Direct Link To This Post Posted: 18 January 2021 at 18:44
The other difference is you take each shot at the lenses’ optimal aperture. Say f5.6 to f8. To get a deeper depth of field you would usually have to close down the aperture, often to around f16. At that point you get diffraction softening the image.

Even then the amount of subject in focus at f16 say, hits a limit that you can exceed with stacking.
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Post Options Post Options   Quote bonneville Quote  Post ReplyReply Direct Link To This Post Posted: 18 January 2021 at 19:15
Tony Northrup has a good video, from his earlier days I guess, that explains and demonstrates focus stacking very well. He also gives a comprehensive walkthrough of the process using photoshop.

My macro shot for this weeks Photo 150 is a stack of 18 images but I don't tend to change the actual focus of the lens, I use a macro slider on my tripod and each individual image is taken after a small turn of the knob to move the camera and lens forward a fraction. Using a remote shutter I avoid any camera shake.

Hope this is of some help dCap


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Post Options Post Options   Quote pegelli Quote  Post ReplyReply Direct Link To This Post Posted: 19 January 2021 at 12:45
Here's a photo of my macro focus stacking set-up. It's a Novoflex macro rail between the camera and the tripod head.



You focus on the closest part of the object and then you move the camera a bit closer, take another shot etc. etc. until you reach the deepest/furthest part of the subject in focus. I usually take steps of ~1/4 of the dof for that distance/focal length/aperture.

I then combine the shots taken in Helicon Focus which processes the multiple frames into one with focus from front to back. There's other software to do it as well (eg. Zerene) but I have only used Helicon.


The technique can also be used in landscape photography, but then you need to manually focus into different "depth" of the landscape scene. Some cameras can do that automatically for you (eg. the new Nikon mirrorless when using an AF lens) but with Sony it will be a manual exercise all the way.
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dCap View Drop Down
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Post Options Post Options   Quote dCap Quote  Post ReplyReply Direct Link To This Post Posted: 19 January 2021 at 12:59
Cool, the 'shooting at f5.6 or f8' bit makes sense.
So you're in the sweet spot of lens resolution, multiple times, but not getting into the smeary yucky f16+ zone.

I can see here that manual focus with like 180' or 270' barrel (and no breathing) would be nice to have.

A couple of the shots I'd seen had 'out of focus' areas and were of flowers that didn't look to be uber close-up (but I'm not a botanist) ... so I was a bit foxed to see the 'focus stacking' mentioned in the text. Now y'all explained it to me.

My own macro work has tended to be in the 1/4 to 1/2 life size zone and often at f4 or f5.6 - for playing with out of focus as much as anything else - so this is all novel to me. Classic (stacking) example that comes to my mind is a fly or spider which is the zone where I've never really ventured (favoring 50mm macros as I do). Thanks for the info.
Walk out if it doesn't feel right
I can tell you're only lying
If you've got something better tonight
Then don't mess up my mind with your crying
Just Walk Out In The Rain
Eric Clapton, 1978
 



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