topic Re: ISO and mirrorless in EOS DSLR & Mirrorless Cameras

ISO change on mirrorless: Real-time change in viewfinder?

stevet1 — Tue, 07 Apr 2026 13:24:49 GMT

I just had a question.

If you change the ISO on a mirrorless camera, do you see the effect in realtime looking through the viewfinder?

Steve Thomas

Re: ISO and mirrorless

justadude — Mon, 06 Apr 2026 14:12:45 GMT

You will see the change in brightness in your EVF (or screen) as you change the ISO, so the answer is yes. However if you can see the difference as far as noise increase... better get a reply from someone with younger eyes than mine. 😆

Re: ISO and mirrorless

FloridaDrafter — Mon, 06 Apr 2026 14:32:36 GMT

@stevet1 wrote:

I just had a question.

If you change the ISO on a mirrorless camera, do you see the effect in realtime looking through the viewfinder?

Steve Thomas

Hello, Steve!

On my R5 and R6 series you see it in real time provided you have "exposure simulation" enabled. As the name implies, it is a simulation, so it's not perfect. But it's close enough to give you a good idea of what your image will look like. I shoot mostly in Tv and Av and keep control of ISO (not auto) and use it to make various adjustments to the leg that isn't primary. I typically do this in Av and can adjust my SS using ISO and exposure sim.

To address the point Gary mentioned, you will be hard pressed to see noise through the tiny EVF and noise has to be really bad to see in on the LCD. So I rely on knowing my camera and what ISO I can get away with.

Newton

Re: ISO and mirrorless

stevet1 — Mon, 06 Apr 2026 15:35:55 GMT

Thank you both.

I accidentally knocked my DSLR (a T8i) off the table the other day, and I seem to have lost my Exposure simulation.

I never could see it through the viewfinder, although I could see realtime changes on my screen during Live View.

Alas, that doesn't seem to be working now. Everything else seems to be performing well.

I've been considering upgrading to an R10, and I was just curious.

Steve Thomas

Re: ISO and mirrorless

stevet1 — Tue, 07 Apr 2026 19:30:53 GMT

Newton,

You wrote, "On my R5 and R6 series you see it in real time provided you have "exposure simulation" enabled."

Is there a setting somewhere in the menu system to enable or disable exposure simulation?

I've looked on my T8i and can't find such a setting, and my manual doesn't say anything about such a setting. It appears to be on by default.

Steve Thomas

Re: ISO and mirrorless

FloridaDrafter — Tue, 07 Apr 2026 21:10:21 GMT

@stevet1 wrote:
"Is there a setting somewhere in the menu system to enable or disable exposure simulation?

I've looked on my T8i and can't find such a setting, and my manual doesn't say anything about such a setting. It appears to be on by default."

Hello, Steve!

It's only available in live view. Enable live view and in the menu go to the second red camera tab and select "Expo. simulation" and enable it. As you mentioned, it might already be enabled.

Newton

Re: ISO and mirrorless

stevet1 — Wed, 08 Apr 2026 01:31:01 GMT

Newton,

Thanks for the suggestion about Live View. I checked, and my menu options don't list that setting. On my camera, I think Exp Sim is enabled by default.

In the process, I learned that my touch shutter has been killed too, which I don't mind too much, since I never used it, but I did learn one lesson.

Mama don't let your babies grow up to be cowboys. 😄

Steve Thomas