Do you think the image of SD14(SD15/DP1/2) is cleaner than that of SD1m(DP1m/2m) ?

Started Jan 12, 2013 | Questions thread
xpatUSA Forum Pro • Posts: 10,528
Re: The Clark Article is Simply Wrong

Roland Karlsson wrote:

The Clark article is simply wrong.

But Roger Clark is very well respected although sometimes a little hard to follow:

He first says that today´s sensors are photon limited. And then he goes on and says that increasing number of pixels increases noise and decreases dynamic range.

Actually he says it a little differently: "there is one fundamental limit: photon counting statistics", by which he is referring to the signal-to-noise ratio. His table follows:

Photons, Noise, signal-to-noise (SNR)

9 3 3

100 10 10

900 30 30

10000 100 100

40000 200 200

If we agree that these figures are correct, it should be obvious to everyone that the sensor which counts 40,000 photons has a better SNR than that which counts 10,000. Better by a factor of two, do we at least agree on that? Indeed, if we can not agree that photon noise is the square root of the photon count, then our discussion might as well here.

(My only problem is with Clark's use of the word "limit" which is so often inappropriate in the world of photography, since it implies a solid barrier which can not be exceeded. Perhaps a photon count of one?)

That is only correct if you assume that you are going to either crop the image or enlarge it so that the pixel density is the same in the print, and then also look at the image at the same distance.

Which generally is a bogus assumption.

If you print the whole image at the same size, then there will be no IQ problems with having more pixels, if you are photon limited.

Yes, when we make images the "same size" the implication is that one of the images is re-sampled. Upward and acutance is lost. Downward and acutance is improved.

Moreover - there is ABSOLUTELY not any 5 um limit. The limit is strongly dependent on the technology for the sensor.

I absolutely agree that there is not a 5um limit. In fact, "limit" is not even an appropriate word in this context.

If the technology is such that the percentage of captured photons do not drop when having more pixels, then the noise and dynamic range is not affected at all. We are not there yet, but getting closer for each generation of sensors.

A reasonable conjecture. Meanwhile, I believe the thread is about existing sensors.

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