Jumpy exposure and focus with X-T4 video

Started 3 months ago | Discussions thread
boogisha Senior Member • Posts: 1,460
Re: Jumpy exposure and focus with X-T4 video - auto ISO exposure ramping/stepping

Tony Northrup wrote:

Hey, Fuji experts. I'm doing a comparison of cameras for YouTubers, which means testing things like autoexposure and continuous video AF, and I've run into problems with the Fujifilm X-T4. I hope someone here as figured out a setting or workaround (besides switching to manual, which isn't an option for this type of film-yourself scenario).

  1. The continuous focus is very jumpy. It will lock onto my eyes beautifully, but then abruptly shift away and shift back. I'm using the eye detect AF in C-AF mode. It happened with the 16, 35, and 56mm lenses, in both 1080/60 and 4k/60. Is there anything I can do to improve this?

Far away from an expert, and not doing much video myself, but doesn`t Fuji have some setting to fine-tune focus changes - like whether it should try to stick more with the original target, or quickly jump to a different possible one instead...? Not sure if that would help in this case, though.

  1. Exposure changes are abrupt. Using manual shutter and f-stop and auto ISO, the exposure jumps up unevenly (look at the background in the first two clips of the sample video). Maybe it's doing full 1/3 stop jumps? Is there something I can do to smooth it out?

Besides auto aperture (being the worst on its own), even auto ISO in video is problematic with Fuji still, unfortunately, for the very reason you observed - when scene exposure changes slowly, sudden exposure jumps (while trying to keep exposure the same) are the most obvious.

You may try setting shutter speed to auto, too (if acceptable), as that usually helps - as if shutter speed "increments" are much finer/smaller, where ISO increments are too large(?!) to accommodate fine exposure changes, indeed... :/

This video clip demonstrates the problems: https://www.youtube.com/watch?v=_fyFd43YF4s

FWIW, none of the other cameras we tested (the ZV1, M50, EOS RP, or iPhone) exhibited those problems. Of course, I've also reached out to Fujifilm directly, but they often don't respond.


If enough (and influential) people raise this issue, hopefully Fuji will finally do something about it, it`s way past the time... So, you help us?

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