Sony A77 High ISO RAW
Sony A77 High ISO RAW Comparison
We often look at RAW files converted with dcraw, an excellent freeware raw converter. dcraw usually offers timely support for the latest cameras, but more importantly, it does not apply any noise-reduction, sharpening or other corrections such as geometric distortion correction to the output files. There will always be differences between RAW converters, in terms of the sort of de-mosaicing algorithms they use (the processes by which they convert the separate Red, Green, and Blue data sets to an array of full-color RGB pixels), but dcraw seems to use a fairly generic algorithm that delivers good sharpness with relatively few artifacts, and can be counted on to not apply any noise reduction if you don't want it to. (That said, looking at the ISO 6,400 and above examples below, it's clear that dcraw's de-mosaicing approach does have some tendency to produce rectilinear artifacts in response to high noise levels.)
See crops below to compare the A77's High ISO RAW image quality to a couple of leading SLRs: the Canon 60D and Nikon D7000. We also include the Sony NEX-7 here, which shares a similar if not identical sensor.
Here, we can see the A77 doesn't perform as well as the 18-megapixel Canon 60D at the pixel level, though that's not a surprise given the 60D's larger photosites (4.3µm vs 3.9). The 16-megapixel Nikon D7000 also does better at the pixel level, with its larger 4.8µm photosites. (Note that the Nikon D7000 tops out at ISO 25600, not shown here.) The Sony A77's RAW files do look very similar to the NEX-7's, though they are slightly noisier. We assume the light lost through the A77's transflective mirror is to blame, requiring the A77 to amplify its sensor output more than the NEX-7 for the same exposure.
See crops below to compare the Sony A77's RAW image quality to some additional hi-resolution cameras.
The Nikon D3X, which is included here because it has similar resolution (24.5MP), does quite a bit better than the A77, but at four times the cost, it's not exactly a fair comparison. The Sony A900 also does better than the A77, though that's also not a surprise since it too has larger photosites, as both the D3X and A900 are full-frame models with 5.9µm photosites. The 20-megapixel APS-C Samsung NX200 does quite well, though, performing a little better than the Sony in terms of noise, with its larger 4.3µm photosites.
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