I don't claim to know if the K-3 is or is not more noisy than the K-5. I'm just talking about the fundamental question of noise in more vs. fewer pixels. Read noise, etc., is a whole other ball of wax, but photon statistics is the one thing that you can't get away from with ever-improving technology. Throw different in-camera jpeg engines into the mix and really this is a comparison not worth making, if you want a basic understanding of how pixel count relates to noise.
I remember in the original glowing DXO reviews of the K-5 they mentioned that some noise reduction is applied even to RAW files at high ISO. On Wed, Aug 6, 2014 at 10:45 AM, Zos Xavius <[email protected]> wrote: > That's not factoring in read noise, processing and quite a few other > variables. My take is that the K-5 series produces cleaner files out > of the box at any ISO. How much I can push shadows without seeing > noise is of great interest to me. I feel that you can likely get files > from the K-3 with equal noise characteristics with post processing, > but honestly, side by side jpegs out of the camera reduced to web > resolution show more noise from the k-3. Also you have to factor in > the resolution loss when the k-5 hits over 1600. Its clearly doing > some NR wizardry in its pipeline and reducing the resolution somewhat. > How much the K-3 does that I do not know, but have read that it does > something similar. > > On Wed, Aug 6, 2014 at 10:07 AM, Bryan Jacoby <[email protected]> wrote: >> It's all about photon counting statistics a.k.a. Poisson statistics >> a.k.a. shot noise: http://en.wikipedia.org/wiki/Shot_noise >> >> If we ignore the mysteriuos details of de-Bayering (let's pretend all >> cameras are like the Leica M Monochrom), and that we are in a >> situation where photon counting statistics are the dominant source of >> noise (which is what we should be talking about, since we are >> concerned with the fundamental question of noise in more vs. fewer >> pixels, not other noise sources that will vary from one sensor design >> to another), then all that matters is how many photons end up each >> pixel of the final output image. >> >> Consider this simple case: you want to order an 8 x 12 print from >> Mpix, which they will print at 250 dpi, for a final output image with >> 6 MP, and we don't do any noise reduction. >> >> If you take the image with a 6 MP sensor (kind of like a K100D >> Monochrom, but with a modern sensor), each sensor pixel/photosite will >> translate directly to an output pixel, so input or sensor image noise >> = final image noise. >> >> If you take it with a 24 MP sensor (K-3 Monochrom), each photosite >> will on average get 1/4 as many photons as the K100D's photosites. >> Poisson statistics tell us that the noise goes as the square root of >> the number of photons, so each of these pixels will have a >> signal-to-noise ratio (SNR) that's only half of the SNR of the K-3 >> pixels. But when you average together groups of 4 pixels from the >> K-3, the SNR of the aggregated pixels will increase by the square root >> of 4, which is 2. 1/2 * 2 = 1; like I said it all comes out in the >> wash. >> >> On Tue, Aug 5, 2014 at 5:38 PM, steve harley <[email protected]> wrote: >>> on 2014-08-05 13:50 Bryan Jacoby wrote >>>> >>>> I think this idea of bigger/fewer pixels leading directly, as in >>>> through the very basic physics of photon noise, to lower noise is >>>> wrong-headed.I couldn't care less what the signal-to-noise ratio of >>> >>>> _pixels in my sensor_ is. What I care about is the SNR of pixels in >>>> the output image, whether that be an image displayed on a screen or >>>> the dots made by a printer. >>> >>> >>> i have pondered this too, and i suppose the question is whether one could >>> average the pixels on a 24 Mp sensor to get as clean a 12 Mp image as from a >>> 12 Mp sensor; i suspect there are multiple factors beyond the number of >>> photons hitting a photosite that make the relationship non-linear (so that >>> lower Mp would net lower noise even after averaging) >>> >>> but since in general we'd expect the 24 Mp sensor, in bright enough light, >>> to capture much more detail with a comfortably low noise floor, i think we >>> have to choose between low-ISO detail and high-ISO SNR >>> >>> >>> >>> -- >>> PDML Pentax-Discuss Mail List >>> [email protected] >>> http://pdml.net/mailman/listinfo/pdml_pdml.net >>> to UNSUBSCRIBE from the PDML, please visit the link directly above and >>> follow the directions. >> >> -- >> PDML Pentax-Discuss Mail List >> [email protected] >> http://pdml.net/mailman/listinfo/pdml_pdml.net >> to UNSUBSCRIBE from the PDML, please visit the link directly above and >> follow the directions. > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and follow > the directions. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
