Focus Each Frame?

I’m looking for feedback on whether people auto-focus (or manual focus) for each negative frame, or if you set the focus on the first one and keep it on manual for the rest. If we assume the setup is stable is there a benefit to auto-focus that you all have found or is it a waste of time?

I set focus, the distance between the camera and the film does not change in my setup

Thanks for that. I was wondering if very slight differences in curvature of the negative strips would impact the focus distance or if it’s negligible (assuming they’re not completely curled). I suppose if the negative holder keeps things consistently very flat that would be a consideration. My home-made negative holder may or may not be good at that…perhaps I’ll find a bowed negative strip and do a couple of A/B comparisons against a really flat one.

I typically re-focus for each frame (using autofocus). It seems that with the depth of field being so shallow with the macro lenses, any slight variations in the curve of the film might affect the focus. But at times, my camera does not want to focus well on each frame and I’ve just turned autofocus off after getting a good capture.

On a DSLR with an optical viewfinder, I found manual focusing was required - the auto focus wasn’t precise enough and usually nudged the focus out of whack even when starting from perfect focus. I usually set focus once per roll using the first sharp frame in the roll, then don’t touch focus until the next roll or if I take a break. I’ve found using the optical view finder is the easiest and most accurate way to focus, since your eye has a good feel for when the focus peaks across the whole image as you adjust the lens.

I’ve recently changed to a mirrorless camera in the same system and will be interested to see if this autofocus situation has changed (once I’m in the same locations as the negatives I’m working through).

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I manually focus the first image on each negative strip. I find that focus will vary from strip to strip as film curvature can vary slightly from strip to strip. I’m using a Sony A7riii and the Lomography film holder.

As I started doing DSLR scans with my wife’s photography equipment, I quickly realized that macro photography is sensitive to sub-millimetre variations in focus. A manual focus on one frame would be unfocused on the very next frame. So I experimented with switching to autofocus, and it actually works well! In my experience doing a few rolls so far, autofocus properly focuses on the film grain every time. I would just suggest disabling any face-focusing feature in the camera.

Also, I believe I remember Nate talking about using autofocus in one of his NLP videos.