topic Re: How do you disable auto-ISO on R6 III in video mode? in EOS DSLR & Mirrorless Cameras

How do you disable auto-ISO on R6 III in video mode?

stokestack — Mon, 15 Dec 2025 04:00:12 GMT

I can find no way to disable auto-ISO in dedicated-video mode on the R6 mark III. I've dug through every menu multiple times, and even assigned ISO-setting to the multi-function button in both stills and video mode. The documentation

Pressing it in stills mode does indeed bring up the ISO-setting screen. But in video mode it does nothing. This seems like a bug. Before I return the camera, I'd like to exhaust all info sources. The documentation is garbage, the worst manual I've seen in decades.

Re: How do you disable auto-ISO on R6 III in video mode?

shadowsports — Mon, 15 Dec 2025 11:35:04 GMT

Greetings,

Try selecting Movie aperture priority.

Canon : Product Manual : EOS R6 Mark III : Movie Aperture-Priority AE https://share.google/sXyQbWY9rmtJOSnIA

Re: How do you disable auto-ISO on R6 III in video mode?

stevet1 — Mon, 15 Dec 2025 14:58:13 GMT

stokestack,

On my camera (a T8i), I can shoot video in either Manual Mode, or in one of the semi-automatic Modes. If I use Manual, I have control of all the settings: shutter speed, aperture and ISO.

If I use one of the semi- automatic Modes (TV, Av, or P), the camera defaults to the P, or Program Mode, and the camera chooses the settings, although I still might be able manually select a different ISO (I'll have check on that one).

Steve Thomas

Re: How do you disable auto-ISO on R6 III in video mode?

shadowsports — Mon, 15 Dec 2025 15:22:34 GMT

Greetings ,

Thanks Steve, I should have mentioned that.

In manual mode you are responsible for shutter speed, aperture and ISO.

Re: How do you disable auto-ISO on R6 III in video mode?

stevet1 — Mon, 15 Dec 2025 20:24:03 GMT

stokestack,

I just tested it out, and when I am in one of the semi-automatic modes on my T8i, (Tv, Av, or P), the ISO function is not available to me.It defaults to Auto ISO and I can't change that.

I can only make changes to my ISO if I am Manual Mode.

Steve Thomas

Re: How do you disable auto-ISO on R6 III in video mode?

stokestack — Mon, 15 Dec 2025 21:12:02 GMT

Thanks for taking the time to do that.

Wow. That's a major design blunder. If we can't prevent the camera from degrading image quality "automatically," without giving up all automatic modes, that's a deal-breaker and probably the last straw for Canon in my gear collection.

Re: How do you disable auto-ISO on R6 III in video mode?

stevet1 — Tue, 16 Dec 2025 00:52:03 GMT

stokestack,

I actually like taking videos in Av Mode. My camera quickly adjusts the exposure to match the lighting conditions as you move from shady conditions to brightly lit ones. I don't have stop and fiddle with the settings to get a good exposure.

And with Movie Servo, I don't have adjust the focus either. The camera focuses for me.

Steve Thomas

Re: How do you disable auto-ISO on R6 III in video mode?

Waddizzle — Tue, 16 Dec 2025 01:20:16 GMT

The only time the camera overrides your ISO setting is to correct for an under/over exposure.

In stills mode the behavior is called Safety Shift.

Re: How do you disable auto-ISO on R6 III in video mode?

stokestack — Tue, 16 Dec 2025 02:58:30 GMT

Right, but according to your tests, you can't set the ISO in Av mode either. For video, I would want to use Tv mode, so motion is always rendered the same way. And you absolutely don't want your video quality fluctuating... and that means you don't want your ISO changing by itself.

Re: How do you disable auto-ISO on R6 III in video mode?

stokestack — Tue, 16 Dec 2025 03:04:41 GMT

Yes, I'm aware of that. But forcing the user to accept fluctuating image quality is absurd. Cameras in Program mode normally adjust aperture and shutter speed as far as possible to meet the needs of the scene, and then warn you when they can't do so. Then you can decide to change ISO, change your lighting, change your lens, or whatever. Having auto-ISO is fine as an option, but totally unacceptable for those who need to maintain image quality.

Re: How do you disable auto-ISO on R6 III in video mode?

stevet1 — Tue, 16 Dec 2025 04:10:27 GMT

stokestack,

A couple of things:

1) Modern cameras are capable of handling higher ISO's than they used to.

2) For a fixed setting with constant lighting, using Manual Mode, where you dial in your settings yourself this will work just fine; but if you are in a setting where the light is constantly (and maybe quickly) changing, Manual Mode may actually work against you.

3) I could be wrong here, but on my camera at least, I'm pretty sure that when I use a semi-automatic mode, the camera sets a shutter speed that is twice the frame rate, i.e. at 30fps, it will set a shutter speed of 1/60th of a second. According to a lot of people, this the most natural flow of movement. Slower than that and you get fast, jerky movements. Faster than that and you get slow motion video.

If 1/60th risks overexposure, a lot of videographers will use a 3 stop ND filter to cut the light.

Steve Thomas

Re: How do you disable auto-ISO on R6 III in video mode?

stokestack — Tue, 16 Dec 2025 08:48:27 GMT

Thanks for that, but it doesn't really have anything to do with the problem here. The whole point is to prevent the camera from changing the ISO (and the image quality).

As far as the shutter speed goes: You're pointing out another problem with this camera, which is the lack of a shutter-angle setting. In video mode, it shouldn't be referring to "shutter speed." When shooting video, it's customary to set a shutter "angle," which automatically changes with frame rate to ensure valid values. The term "angle" refers to circular mechanical shutters found on motion-picture cameras, where exposure time was determined by adjusting the size of a pie-shaped opening in the shutter disc.

And yes, the "normal" shutter angle is 180 degrees, which results in a shutter speed 1/2 the frame rate.

Re: How do you disable auto-ISO on R6 III in video mode?

stevet1 — Tue, 16 Dec 2025 15:13:04 GMT

stokess5ack,

Well, I guess the only way to prevent your camera from changing your ISO is to shoot in Manual Mode. (Unless your R6III behaves differently than my T8i).

Steve Thomas