ETTR and how it relates to the scene-referred workflow and filmic

[kmilos]

@jorismak

Raising iso (often) raises the gain on the amplifier, boosting the signal but also boosting the noise that was already there.

Yes, but not necessarily proportionally for both signal and noise as you think. For some sensors/cameras there is an advantage in shadow SNR when shooting at higher ISO, as @Matt_Maguire pointed out. Again, Emil Martinec provides an excellent explanation of ETTR misconceptions and ISO use here.

@Matt_Maguire

However, sometimes varying the ISO can really affect the response of the sensor, and this can improve the SNR. For example, in the Sony A7R4, once you hit an ISO around 320, this causes a sort of “preamp” to kick in, which can be helpful.

For the interested, you can check you camera’s behaviour at Bill Claff’s indispensable site, I’m linking and example for the A7R4 mentioned, indeed showing a step at ISO 320 giving you an extra 1/2 stop in the shadows if your highlights are not a priority.