ISO setting effect on noice in raw format?

Started Sep 1, 2009 | Discussions thread
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OS74
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ISO setting effect on noice in raw format?
Sep 1, 2009

I wonder if anyone can enlighten me on how the ISO setting affects the sensor reading.

Recently i had to photograph in low light underwater hand held, and deemed that 1/40 and 2.5 (max aperture) was the limit acceptable for motion blur and camera shake. I saved the pictures in RAW format. (Ricoh Caplio GX100)

I tried to use both the camera's setting ISO 80 and ISO 200. However in post processing, I increased exposure a stop or so. Now I still liked the result on ISO80 better.

A JPEG would have 8bit pixel information, while the RAW file has 12bit, so the increased headroom of the raw was used to increase the exposure.

My question is if the ISO affects the gain when the pixels are read, before digitization or after when JPEG is generated? And how does ISO-change apply actually?

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