Get less ISO noise at higher ISO sensitivity

dolina

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This has been verified by me with EF bodies from 2003 EOS 10D up to 2015 EOS 5Ds R.

RF bodies like the 2020 EOS R5 & 2022 EOS R7 may have this. Owners may want to verify.

To reduce whatever ISO noise Canon has a weird ISO increments of every ISO 160.

So ISO

- 160
- 320
- 640
- 1250
- 2500
- 5000
- 10,000
- so on and so forth

These ISOs are cleaner than the next 1/3rd bump or bump down
 

Ysarex

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This has been verified by me with EF bodies from 2003 EOS 10D up to 2015 EOS 5Ds R.

RF bodies like the 2020 EOS R5 & 2022 EOS R7 may have this. Owners may want to verify.

To reduce whatever ISO noise Canon has a weird ISO increments of every ISO 160.

So ISO

- 160
- 320
- 640
- 1250
- 2500
- 5000
- 10,000
- so on and so forth

These ISOs are cleaner than the next 1/3rd bump or bump down
This info is a bit dated -- it's no longer an issue with newer cameras as read noise has been substantially engineered out of our newer cameras and so there's no longer much if any benefit to analog ISO amplification as a noise suppressant.

For an older Canon camera like a 5diii this phenomenon did show read noise variation between whole stop and intermediate 1/3 stop increments such that a photo taken at a higher ISO would appear less noisy than a photo taken at a 1/3 stop lower ISO. What Canon did was only apply analog amplification in full stop increments. The intermediate 1/3 stops were just scaled in the ADC. Implementing an ISO increase by applying analog signal amplification suppresses read noise whereas implementing an ISO increase via scaling does not.

I copied a graph of read noise over ISO for the 5diii from Photons To Photos (credit Bill Claff -- thanks Bill) and made some annotations so you can see what's going on.

claff-noise.jpg


Canon and other manufacturers may still be using the same method of implementing ISO increases but there's no longer a visible difference for us to detect because read noise in our modern cameras has been beaten down to negligible.
 

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