Jumpy exposure and focus with X-T4 video

Started 3 months ago | Discussions
Tony Northrup
Tony Northrup Regular Member • Posts: 124
Jumpy exposure and focus with X-T4 video
1

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?
  2. 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?

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.

Help?

Canon EOS M50 (EOS Kiss M) Fujifilm X-T4 Sony ZV-1
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Bob Tullis
MOD Bob Tullis Forum Pro • Posts: 39,635
Yes, those have been noted

Those issues with video AF and slow panning with IBIS have been noted and discussed earlier. You can probably find the topics with a search if interested.

Your video link returns a "Private" &  unavailable message. I don't know if it has to do with your commercial affliction and a DPR conflict with such, or if you've not given it full public access.

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Tony Northrup
OP Tony Northrup Regular Member • Posts: 124
Re: Yes, those have been noted

Thanks for the info (even though it's not the answer I hoped for). I fixed the YT video link so it should work now.

boogisha
boogisha Senior Member • Posts: 1,460
Re: Jumpy exposure and focus with X-T4 video - auto ISO exposure ramping/stepping
1

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.

Help?

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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boogisha
boogisha Senior Member • Posts: 1,460
Re: Jumpy focus with X-T4 video - AF-C CUSTOM SETTINGS?
1

boogisha wrote:

Tony Northrup wrote:

  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.

There, did a quick lookup in X-T4 manual, you might want to check what difference fiddling with movie mode menu "AF/MF SETTING > AF-C CUSTOM SETTINGS[1]" does, if any:

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boogisha
boogisha Senior Member • Posts: 1,460
Re: Jumpy exposure with X-T4 video - auto ISO exposure ramping/stepping
1

boogisha wrote:

Tony Northrup wrote:

  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... :/

For the reference, here is one of the more recent threads where we discussed Fuji video exposure stepping/ramping, mainly caused either by auto aperture, or auto ISO:
"X-T4, Exposure stepping in Shutter Priority still makes video basically useless"[1].

It`s not a long thread, and might be worth checking, as it touches and rehashes some of the previous discussions, too.

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Tony Northrup
OP Tony Northrup Regular Member • Posts: 124
Re: Jumpy exposure and focus with X-T4 video
4

For future people troubleshooting these problems, I escalated this to the Fuji product team and they suggested turning off eye detect AF (using face detect only). I also took boogisha's recommendation to adjust the tracking sensitivity.

I tested all combinations of settings and got the best AF results with Face Detect (no eye detect) and AF tracking sensitivity set to +4. If you have to use continuous AF in video, try that.

Unfortunately, those results were still very unacceptable... AF still jumps in and out. I'm offering my recordings and assistance to the team at Fujifilm with the hopes a future firmware update could fix both the AF and exposure stepping... I don't see any reason it couldn't.

Fingers crossed!

Jacaustin Forum Member • Posts: 79
Re: Jumpy exposure and focus with X-T4 video

Thank you Tony. Hope this contributes to a firmware fix.

Fuji Maine Contributing Member • Posts: 932
Re: Jumpy exposure and focus with X-T4 video

Tony if you can get your hands on a Fringer adapter and a copy of the sigma 18-35 zoom give that a try. If the 16 and 35mm lenses you are using are the 1.4 versions than you're choosing three awful lenses for AF performance. I have none of those issues on my XT4 with the sigma lens. The XT4 is phenomenal for video, you just have to use third party glass! I'm not familiar with your YouTube channel but if you're comparing video specs you should consider discussing how someone would use the camera for real life hired work and not just how some internet tool uses it to record themselves on a tripod or with a selfie stick. Just my two cents.

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