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.
