Quarkcharmed on ISO and raw files

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bodeswell Regular Member • Posts: 324
Quarkcharmed on ISO and raw files
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In another thread Quarkcharmed has been talking about ISO, but this has occurred as a sidebar to a discussion of the Sunny 16 rule. I do not want to discuss that rule.

I am not clear on what Quarkcharmed is saying about ISO, bandwidth and raw files.

I have been trying to piece it together and I *think* that he is saying that as one goes to each higher (partial) stop on the ISO dial "the bandwidth changes" and so the amount of  information that can be saved in the raw file changes, in fact, it decreases.

I find the whole subject of the relationship of the ISO dial to the raw file ... mysterious.

The only thing the ISO standard 12232 has to say about raw files is that it doesn't have anything to say about raw files. This is not a discussion of the standard. It is a discussion of the dial.

I am perfectly willing to believe that manufacturers do more than tweak jpeg lightness as the ISO dial turns. However, my impression is that whatever they do aside from tweaking lightness is neither regular nor predictable, neither standardized nor documented, and it can only be inferred empirically unless one happens to work on sensor design for a manufacturer.

Quarkcharmed seems to be saying that something much more regular is happening across manufacturers and camera lines, so much so that it ought to be considered before one uses Auto ISO. Why?

I have strong Auto ISO leanings myself (up to 6400), but I like setting the aperture and shutter speed.

Disclaimer: this is not a discussion of "exposure". I adhere to the orthodox and only correct usage that the "exposure" is the quantity of light that reaches the sensor, governed by aperture and shutter speed alone among camera controls. The ISO dial has no control over that quantity of light.

 bodeswell's gear list:bodeswell's gear list
Canon EOS R Canon EOS 90D Canon EOS R5 Tamron 18-400mm F3.5-6.3
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