topic Re: ISO Invariance in EOS DSLR & Mirrorless Cameras

ISO Invariance on EOS R5 or R5 Mark II

tangogal — Tue, 28 Oct 2025 14:45:21 GMT

Are either the R5 or R5 Mark 2 ISO invariant?

Re: ISO Invariance

shadowsports — Tue, 28 Oct 2025 00:03:45 GMT

We love these types of questions. 😍 Yours is a good one. Yes, both cameras are ISO. Invariant. A key trait of this feature is dual-based ISO. Although this applies to video, the camera's sensor in both cameras allows you to underexpose still images using a lower ISO, (maintaining contrast and details in shadows) then raise the exposure in post without amplifying noise introduced by higher ISO settings.

If you are considering these body's, you should look at the different ways each handles ISO. Youtube might be a helpful resource.

Re: ISO Invariance

Peter — Tue, 28 Oct 2025 12:38:30 GMT

It seems like the link I posted hanged the webpage here. Glad a moderator removed it.

Here is a print screen instead.

From the author:

"The amount of improvement in the shadow measurement when ISO is increased is what I am calling the PDR Shadow Improvement.

For those shooting raw it can be useful to know when raising ISO in the camera has little or no advantage over applying digital gain in post processing.
(Some people call this property "ISOless". I think that is a very poorly chosen term.)"

R5 and R5 II with electronic shutter will have a different curve. R5 in high speed too.

Re: ISO Invariance

shadowsports — Tue, 28 Oct 2025 14:55:10 GMT

Peter,

Thanks for mentioning the bit about electronic shutter. 👍

Re: ISO Invariance

tangogal — Tue, 28 Oct 2025 15:01:04 GMT

I can't read the chart you posted called Photons to Photos. Can you post the link again?

Thanks.

Re: ISO Invariance

johnrmoyer — Tue, 28 Oct 2025 15:14:39 GMT

@tangogal wrote:

I can't read the chart you posted called Photons to Photos. Can you post the link again?

Thanks.

https://www.photonstophotos.net/Charts/PDR_Shadow.htm and click on the camera you are interested in.

Also https://www.photonstophotos.net/Charts/PDR.htm

Re: ISO Invariance on EOS R5 or R5 Mark II

Waddizzle — Wed, 29 Oct 2025 07:01:53 GMT

“ A key trait of this feature is dual-based ISO. Although this applies to video, the camera's sensor in both cameras allows you to underexpose still images using a lower ISO, (maintaining contrast and details in shadows) then raise the exposure in post without amplifying noise introduced by higher ISO settings. “

Exactly why I typically shoot with -1/3 Ev of compensation. My LR import preset increases the exposure to compensate. Especially with outdoor landscape photos.

I have been doing this for years, going back to my DSLR days. I would rather under expose shadows than push the limits of highlights.

Re: ISO Invariance

tangogal — Tue, 03 Feb 2026 17:09:53 GMT

what are the 2 base ISOs for the R5 and R52? I know ISO 100 is the first but what is the second?

Re: ISO Invariance

johnrmoyer — Tue, 03 Feb 2026 17:45:18 GMT

@tangogal wrote:

what are the 2 base ISOs for the R5 and R52? I know ISO 100 is the first but what is the second?

I have seen different numbers reported for the EOS R5. It might be different for video, but i do not do video.

Between ISO 250 and ISO 320 the blacklevel numbers in metadata change and that might be a hint. The change in blacklevel should be used when processing raw files.

I have also read that ISO 400 is when the EOS R5 camera starts using the second gain level.

Here are measurements comparing the two cameras.

https://www.photonstophotos.net/Charts/PDR.htm#Canon%20EOS%20R5,Canon%20EOS%20R5%20Mark%20II