Pixel density - can the playing field be leveled???

Started Jun 6, 2009 | Discussions thread
Steen Bay Veteran Member • Posts: 7,418
Re: Per area read noise?

John Sheehy wrote:

Steen Bay wrote:

Is it correct that a hypothetical 20mp G11 would have 1 stop higher per pixel (and 'image level') noise and 1 stop less DR than a 10mp G11, assuming a 'perfect scaling' of the read noise? And if the read noise isn't scaled, if the 20mp camera has the same per pixel read noise as the 10mp camera, won't the difference in DR and in the shadow/high-ISO noise then be larger than 1 stop?

Define "read noise"; IOW, what are the units?

If read noise is a value relative to saturation or metered gray, in ADUs, then "the same" pixel level read noise will decrease image read noise to 71%. If we are measuring in electrons, then maintaining read noise at the pixel level will increase read noise by 41%.

By a 'perfect scaling' I mean scaling the read noise with the pixel size like Emil described above. If for example the 10mp camera's read noise was 7,1 electrons, then the 20mp camera's per pixel read noise should be 5 electrons, in order to maintain its relative value, compared to the shot/photon noise. And by 'the same read noise' I mean the same absolute level of of read noise, like for example 7,1 electrons for both cameras. (And although both the scaled per pixel read noise and the shot noise would be lower in absolute values, then its level, measured in percent of the signal would be 1 stop (41%) higher, resulting in 1 stop lower DR for the 20mp camera)

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