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

Started Jun 6, 2009 | Discussions thread
Cheburashka Regular Member • Posts: 297
Re: 10mp vs 20mp

Steen Bay wrote:

P.S. - Actually it isn't quite correct to say that the image level shot noise is the same regardless of pixel count. That assumes a 'perfect' downsampling of the 20mp image to 10mp. The 'constant noise' argument is only valid when comparing at the same 'spatial frequency' or resolution. As it is, with its higher resolution, the 20mp image has 41% higher 'image level' shot noise, since the signal is the same for the sensor as a whole, and the sum of the per pixel shot noises is 41% higher.

If we are comparing two systems on the basis of noise performance, then it only makes sense to do so at the same level of detail. To do otherwise artificially penalizes the more detailed image since the extra detail could be traded for less apparent noise via NR (noise reduction) and/or downsampling.

Regardless, there still isn't more photon noise in the 20 MP image. It's just that the noise is resolved more clearly, so it's more visible. The 10 MP sensor blurs the noise that is already there, just as it does with the detail, which gives the impression that there is less noise, even though the noise content is the same.

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