Sony DSLR-A580 High ISO RAW
Sony A580 High ISO RAW Image Quality
We 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 as some other converters do. There will always be differences between RAW converters, in terms of the sort of demosaicing 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.
See for yourself how the Sony A580's high ISO RAW files compare to those from other recent APS-C size sensor models: the Canon 60D, Nikon D7000 and Pentax K-5. Click on any of the crops below to see the corresponding full-sized image.
Here, we can see that the Sony A580's RAW files contain similar amounts of noise compared to the Canon 60D and Nikon D7000 at all ISOs shown, and moderately higher levels than the Pentax K-5. The Pentax K-5 applies some subtle noise reduction to its RAW files above ISO 1,600, though, so it's no surprise the Pentax performs better than the rest of the group in terms of noise at ISO 3,200 and above, however the K-5 is still slightly cleaner at ISO 800 and 1,600. (The other cameras in this group do not apply NR to their RAW files, as far as we can tell.) Some of the differences may be due to exposure, though, as we adjust exposure and lighting for these images so that middle gray on the MacBeth chart is very close to the correct RGB value in the JPEGs. That means differences in tone curves and actual ISO sensitivity can impact actual exposure, making RAW noise comparison more difficult. Keeping this in mind, we'd say the Sony A580 performs competitively compared to the other cameras in this group when it comes to noise in high ISO RAW files.
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