How is ISO determined?

[Daniel Browning]

Is that true for all cameras?

It was true for all cameras until a few years ago.

I thought Canon defined 'native' ISOs as analog gain and 'expanded' ISO as digital gain ("pushing the RAW").

Not really. There is a strong correlation between native ISO and analog gain, but there are several exceptions. For example, on the 5D2, 6400 is a 'native' ISO, but it is based on digital gain (3200 is the highest analog-only gain).

Personally, it doesn't really matter what the highest analog gain is -- I'm more interested in the highest *useful* analog gain. For example, the D7000 has analog gain up to ISO 1600, but going above ISO 200 in raw has only downsides -- no benefits. (Same with going above 1600 on the 5D2 -- although there is a slight reduction in pattern noise, for me it's not usually worth the loss in highlight headroom.)

[Jon Ruyle]

on the 5D2, 6400 is a 'native' ISO, but it is based on digital gain (3200 is the highest analog-only gain).

Really? I was told 1600 was the highest.

If 3200 is the highest analog-only gain, then what do you mean when you say 6400 is 'native'? Do you simply mean it is not an expanded iso?

[Daniel Browning]

If 3200 is the highest analog-only gain, then what do you mean when you say 6400 is 'native'? Do you simply mean it is not an expanded iso?

Yes, that's what I meant.