Tutorial: Deflickering images for focus stacking

Started by TheLostVertex, April 27, 2014, 01:22:23 AM

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TheLostVertex

For some time now I have had a flash that I use for macro photography which does not produce very consistent exposures. When I saw the deflicker module in magic lantern I thought it would be a good way to make use of the misbehaving flash.

The full write up for the technique is here http://www.thelostvertex.com/2014/04/deflicker-images-for-focus-stacking-with-magic-lantern-and-lightroom/

The basic workflow is simple. Enable post deflicker, check to make sure the offset for the sidecar files is acceptable, shoot the sequence, import into Lightroom, set auto white balance to correct subtle changes in color temperature, and then grade the images for export and stacking.

I imagine this would also be useful for focus stacking when doing natural light exposures in cloudy conditions as well, though i have not had a chance to test.

Marsu42

Quote from: TheLostVertex on April 27, 2014, 01:22:23 AMI imagine this would also be useful for focus stacking when doing natural light exposures in cloudy conditions as well, though i have not had a chance to test.

Well, your approach is basically to fix a broken flash - if you use the flash delay and leave the flash enough time this should be no problem for most people.

But if you would mix outdoor ambient with different flash exposure a global exposure correction via deflicker would be no good, same thing as cloudy weather with some sun in between - if the lighting direction changes, your stack is broken. That's why I'm about to get a "softbox tent" to built around objects like mushrooms, everything else is a pita unless you've got very stable weather (either cloudy or sunny, the latter with no objects like moving leaves in the light path).

TheLostVertex

Quote from: Marsu42 on April 27, 2014, 08:54:01 AM
Well, your approach is basically to fix a broken flash - if you use the flash delay and leave the flash enough time this should be no problem for most people.

Well, sort of. According to Sigma it is not broke(though i consider it so), and it being off by up to 1ev is 'normal' according to their tech and customer support departments. I have also used many older flashes that vary about .5EV with regularity. I have not had a change to use any Canon/Nikon branded flashes, but I would not imagine having the same issue. It is also not an issue for using a studio strobe, which produces perfect exposures for me.

For clarity sake, delay between flash firing is not a factor in the differences for the units I have tested.

Quote from: Marsu42 on April 27, 2014, 08:54:01 AMBut if you would mix outdoor ambient with different flash exposure a global exposure correction via deflicker would be no good, same thing as cloudy weather with some sun in between - if the lighting direction changes, your stack is broken. That's why I'm about to get a "softbox tent" to built around objects like mushrooms, everything else is a pita unless you've got very stable weather (either cloudy or sunny, the latter with no objects like moving leaves in the light path).
It wasnt my intention to imply that diffusion would not be used for outdoor exposures. Instead I meant variance between exposures as the amount of cloud cover subtly shifts. Again, not something I have spent much time on, so I do not know how much of a problem it would be.

Marsu42

Quote from: TheLostVertex on April 28, 2014, 12:36:02 AM
Instead I meant variance between exposures as the amount of cloud cover subtly shifts.

Unfortunately, moving clouds don't just change the global exposure level but always change lighting direction and characteristic a bit (or I wouldn't have had so many broken outdoor focus stacks :-p).