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Old 30-01-2008, 02:12 AM
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citivolus (Ric)

citivolus is offline
Join Date: Sep 2007
Location: Carindale
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Originally Posted by skwinty View Post
1.At high iso the camera amplifies signal as well as noise by the same amount therefore no change to signal to noise ratio therefore no advantage to raw at high iso.
The noise is sampled adequately at low iso.
I'm not certain I follow the logic here. Raw will still get around the JPEG artefact problem, where noise in the image generates error in adjacent pixels due to the JPEG compression algorithms. Raw will always out-perform JPEG for captured image fidelity unless you are shooting a 100% flat monochrome frame at ISO 100 with a very low noise sensor.

Additionally, the readout signal to noise ratio in the 40D has been shown to improve even up to ISO 1600, meaning that faint signal will be able to be detected over the background noise more effectively if your sub frames are shot at ISO 1600 than at ISO 400, for example. See . Even if the strong signals are amplified as much as the noise, that lower readout noise floor does provide an advantage to shooting at high ISO, and due to the artefact issues mentioned above, shooting in raw will provide better data.

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