D600 High ISO in DX

Started Nov 23, 2012 | Questions thread
Senior MemberPosts: 1,046Gear list
Roger's optimum pixel pitch of 5um
In reply to bobn2, Nov 23, 2012

bobn2 wrote:

Leo360 wrote:

The resolution of a digital image depends (among other things) on your sampling rate (Nyquist theorem) and pixel size has A LOT to do with it.

Yes, but you were talking of the resolution of a pixel. There is no 'resolution' at a pixel level, only when you look at areas containing many pixels.

I think you misunderstood what I said. Resolution of a single sample makes no sense and I never talked that way.

With proper down-sampling (bicubic, etc) to the same level of detail one can hope to recover the SNR back by effectively combining outputs of multiple smaller pixels into an aggregate one but doing so does not entirely compensate for read-noise increase.

The 'downsampling' argument is a red herring. All that is required is to look at the images produced the same size.

It is not a red herring. Producing images at the same size with the same dpi means that we have to resample an output of hi-res camera to match the sampling rate of a low-res camera. Otherwise your prints will be of different size (dpi is the same, right?)

That is untrue. You do not resample the output of a high res camera to match the sampling rate of a low res camera. Generally you resample it to match the sampling rate demanded by the output image. You will generally resample all cameras so.

For a fair comparison we have to establish a common bandwidth, i.e. common sampling rate. Hence, resampling. For the sake of argument let this common rate be the sampling rate of the lower-res camera (D600 in DX). I resample D3200 image down to match it.

Correct me if I am wrong, but I think that you will have to jump through several hoops to match 4x4 um pixel SNR to 6x6 um one.

You cannot measure SNR in a single pixel in a single photograph. Now think on the implications of that.

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Did I say anything about a single photograph? To measure pixel readings statistics one shoots repeatedly in controlled environments with constant light, exposure, etc. You get mean, variance, probability distribution etc in due course of statistical analysis.

This now becomes throughly artificial, that you make the multiple observations of the same pixel over multiple exposures. It is not even guaranteed that the noise so observed would match the noise observed in the spatial domain. A thoroughly artificial result of no interest.

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Bob, you brought it "single pixel in a single photograph", not me.   I just replied with the text-book definition of how one samples stochastic processes

Anyway, Roger claims that 5um is the optimum pixel pitch for a CMOS sensor. Should one take it seriously? If yes, then we have a winer -- D800 .


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