ISO Sensitivity / Noise levels (contd.)In-camera High ISO noise reductionA new feature introduced on the EOS 40D is optional 'High ISO Noise Reduction' which can be enabled via C.Fn II-1. As you can see from the graph below this appears to apply stronger chroma noise reduction while maintaining luminance detail (it made almost no difference to luminance noise). This leads to images which have less noticeable color blotch type noise and more film like grain, the only downside to using this option is reduced buffer space in continuous drive. The slight white balance shift you see in the crops below the graph are simply because we didn't re-capture the white balance preset after enabling noise reduction.
Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of luminosity on the vertical axis (note that the standard deviation scale here is magnified 2x compared to the graphs on the previous page). In-camera High ISO noise reduction Off / On (ISO 400 - 3200)
RAW noise reductionAs noted earlier both Digital Photo Professional and Adobe Camera RAW have selectable noise reduction options, both providing control over chrominance and luminance noise reduction independently. Digital Photo Professional provides three levels for each (Off, Low, High), Adobe Camera RAW provides a 0-100 scale for each. It's clear that even when the EOS 40D has its 'High ISO noise reduction' option disabled (as it is by default) there is still some noise reduction being applied by the camera. The graph below demonstrates the differences between various noise reduction options compared to in-camera JPEG. As you can see the camera applies considerably more noise reduction by default than either DPP or ACR and that out of the two ACR does a better job at suppressing noise with its default settings. DPP's noise reduction worked but wasn't as effective as that of ACR which provides much more flexibility with its larger range of NR. Noise reduction comparison at ISO 1600, graph
Standard deviation is on the horizontal axis of this graph, different output options on the vertical axis. Noise reduction comparison at ISO 1600, test chart crops
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