ISO on the R5

Quarkcharmed wrote:

MarshallG wrote:

bclaff wrote:

MarshallG wrote:

Disclaimer: I’m only the messenger.

I’m at a trade show all weekly so I stopped in the Canon booth and spent a long time talking with one of their experts about the R5.

He then me that the R5 sensor slightly boosts voltage as you increase ISO,

Not slight but in proportion to the ISO setting.

and it did so in one stop increments.

True of many Canon bodies including the R5

Intermediate ISO changes are made post sensor read,

True of many Canon bodies including the R5

so he said that you can get a cleaner image at a higher ISO setting that falls on a full stop boundary, than on an ISO setting which is between 1/3 to 2/3 stop lower.

I strongly suspect that the effect on image quality is not noticeable.

So he is absolutely correct, except that it absolutely does not matter in any meaningful way. No point in changing our practices as a result of this.

With all due respect to Bill's analysis, there must be gaps in the raw histogram which I don't see, so potentially it's more complicated than just digital multiplication.

Say if you multiply ISO 400 values to get ISO 500, you have to multiply each value by 2^(1/3) = 1.256, basically 5/4.

With integer digital numbers there will be gaps each 5th value - it won't be contributing to the raw histogram and we'll see the regular gaps.

Well… my eyes tend to defocus and glaze over on the math,  but mostly because a 50,000 foot view of the data shows a basically flat line, nothing spiky.

I don’t entirely understand if Bill’s data is a full representation of performance, reflecting shot noise and other undesirable artifacts… but here again, he’s a well-trusted figure and I conclude he knows what he’s talking about.

When composing a photograph, there is so much data to consider that either you use fully controlled lighting, or else you perform a lot of estimates in your mind based on knowledge and experience. In other words, if I want perfection, I’ll shoot at ISO 100, but otherwise, I’m not going to waste any more neurons fretting about whether ISO 400 vs ISO 500 matters. I conclude it does not, so back to shooting for me.