The Sleeping Giant's Sea Lion

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In SNR graphs for Pentax K-30 and Pentax K5 there is something I do not get.

For ISO after 1600 the SNR doesn't really decrease. Moreover comparing with Nikon D3200, we can clearly see that until ISO 1600 the sensors behave almost the same, after that things change. Is there an explanation for that? Is there any processing done to reduce the noise?

(graph from DxO)

enter image description here

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1 Answer 1

up vote 3 down vote accepted

Most likely some noise reduction is being applied to the RAW files by the camera, in a way that cannot be disabled by DXO.

Someone discovered Sony were applying this technique in at least one model by showing the Fourier transform of a RAW blackframe which clearly demonstrated the high frequencies were missing.

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Pentax definitely applies so NR at ISO 3200 and above, DxO reflects that with the "smoothed" items. It's been discussed in various Pentax forums before, but nobody can really say if it's good or bad... :) –  John Cavan May 3 '13 at 15:21
    
@JohnCavan Anything done to the RAW file that's irreversible is bad IMO, if I want processed files I'll shoot JPEG! –  Matt Grum May 3 '13 at 15:32
1  
That was the opinion of many, true. Having said that, the IQ and detail level still looked better than the others at the same ISO, so it wasn't getting people upset. To be honest, I think that behaviour from Pentax stems from their days with Samsung sensors that were notoriously noisy and required Pentax to do something to make them useful above ISO 800. –  John Cavan May 3 '13 at 15:35
    
From what I've read, Pentax's hardware NR is quite good, better than what can be done in post, and the RAW files are still RAW, so you aren't losing anything significant from an editing latitude standpoint. –  jrista May 4 '13 at 3:28

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