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I "black boxed" sRaw in 5D2 a while ago, and it seems that it deals with colour noise in a slightly different manner than the normal in-camera raw-interpolation. At least as far as I have been able to tell from my calculations from identical sRAW/downsized raw comparisons... This might be that the raw-conversion uses a bigger area for colour estimation, and that might affect perceived "sharpness", but it's not an effect that I've noticed. I did all the comparisons at ISO3200+ though, so this isn't really the same thing. Noise affects sharpness/detail quite a bit - and in noisier pictures than the examples shown here I found no sharpness difference. Only a slightly higher medium frequency contrast, and less (and slightly differently spaced) colour noise.
When it comes to sRaw2, the interpolation is 2:1, so I'd guess that Canon has chosen to
1 - use a bigger area for colour estimation in the raw-interpolation
2 - use 4:1 averaging when downsampling (like binning/averaging. Take the average of four > make one pixel). This is a lot less computationally intensive (less work for the processor in the camera), and actually a lot sharper and more accurate than normal bicubic. The sRaw2 is sharper than downsizing a "normal" raw-conversion to 50% with bicubic, if you measure it by imatest.
My conclusion then was that sRaw was so-so usable, but sRaw2 gave some subtle advantages - when compared to resampling a normal raw. So if you know that you're going to use a picture at <5MP anyway, sRaw2 is actually quite good.
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