Thanks for taking the time to explain this, Daniel.



Quote Originally Posted by Daniel Browning

For an example, take a comparison between pixel sizes of 4 microns and 2 microns:

* If the 2um pixel has read noise that is twice as bad, then the final image has the same read noise.
* If the 2um pixel has read noise that is the same, then the final image has much less read noise.
* If the 2um pixel has more than twice as much read noise, then the final image has more read noise.
I agree with all of this, assuming by “twice as bad” you mean snr is twice as bad, not absolute noise is twice as big (ie, you don't mean sd of a Gaussian distribution of number of electrons of read noise is twice as big for the smaller pixel)

Quote Originally Posted by Daniel Browning
So smaller pixels can be noisier per pixel (by an amount equal to the square root of the difference in size) to achieve the same amount of noise as larger pixels. My position is that, all other things being equal, smaller pixels do tend to be just about that much noisier, and so the final image is just about the same.
Okay, so you're asserting that other things being equal, read noise is inversely proportional to the square root of the size of the pixel? That this is true for photon noise is clearly true, and requires very little knowledge of how the camera works. That it is true for read noise seems less obvious to me (as I said, I would have thought reading a pixel would have caused the same amount of noise no matter how big the pixel is) but I believe you []