D600 High ISO in DX

Started Nov 23, 2012 | Questions thread
noirdesir Forum Pro • Posts: 13,622
Re: Roger's optimum pixel pitch of 5um

Leo360 wrote:

noirdesir wrote:

Leo360 wrote:

I am comparing one 6x6um pixel to an aggregated output of four 3x3um adjacent pixels. Think of it in this way. You have a 36MP FX sensor but the marketing department demands a 9MP camera. instead of creating the new sensor an existing 36MP sensor is taken and the readings from a cluster of 4 adjacent pixels are combined together producing a 9MP output. A competitor comes with a true 9MP camera. The question is which one has better SNR and DR? Of course, this is a stupid example but it illustrates what I mean by aggregation. This aggregation happens in one image. I am sorry, I do not understand what it all has to do with repeated observations you keep mentioning.

You really don't know the answer to that by now? Just compare the E-M5 sensor with the D600 sensor and you have your answer. Not quite a factor of four in total number of pixels but it gets close to a factor of three:

- E-M5: 3.73 μm, QE 53%

- D600: 5.9 μm, QE 53%

Same QE, thus the same photon shot noise.

Yes, photon shot noise per unit area is the same. Shot-noise per single pixel reading is not (they have different areas and therefore, different photon count). Again, Bill Claff's charts give D600 one stop advantage in Dynamic Range over E-M5.

A single pixel does not have any noise. Display a single pixel fullscreen on your monitor and tell me whether you can see any noise in it. And we are comparing here different pixel sizes for the same sensor area. The D600 and the E-M5 don't have the same sensor area (the former is four times as large than the latter). On top of that the E-M5 sensor does keep its low read noise quite down to base ISO as good as the E-M5 but that is seen as an ADC problem not one of the pixel.

Thus, FX camera made up of E-M5 pixels would have 62 MP aggregating the output of such a sensor down to 24 MP would yield the same photon shot noise and an even slightly better read noise than the D600 sensor.

Is it the read-noise std.dev. that should be scaled with the pixel area or the variance. In the latter case the read-noise per common 37.3x37.3um uber-pixel would be the same (I used your summation formula but applied scaling to the variances instead of std.dev). Also you are neglecting the dark current which gets stronger more pixels are combined.

As far as I understand it the std. dev. is the thing that should scale with the area. And dark current is second order effect for the pixel size we are discussing here.

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