More megapixels, better photos: Fact or fiction?

Started Feb 7, 2008 | Discussions thread
John Sheehy Forum Pro • Posts: 21,587
Re: An image of course

Chato wrote:

His argument is a cliché, All things being equal, the more MP the
better. Whoa, how original! (now if only we could get rid of those
technical problems that manufacturers seem to have a problem with)

No, Dave; you don't even seem to understand what my argument is, or you're trying to make me look stupid by creating the illusion that I'm rambling on about something that everyone already knows. No one, including myself, has disputed the fact that more pixels of the same quality each, is always better.

My argument is that you can maintain the same image noise, even while increasing pixel density, with the noise per pixel actually increasing to some degree. This happens automatically with shot noise, if you maintain the same QE, because that's just how the math works out. 4 pixels in the space of one means 1/4 as many photons each, and hence double the shot noise (relative to saturation). 4 pixels combined divides the shot noise by 2, and you're back to the original shot noise. Another way to look at it is that For read noise, things can actually improve with a higher pixel density, as real world read noise does not have to increase as fast as shot noise does at the pixel level, when you increase pixel density. If read noise increases by the ratio of the old pixel pitch to the new pixel pitch, image read noise will remain the same. If the pixel read noise of the higher-density pixels remains the same, then the image read noise will decrease. If the read noise per pixel actually decreases (as it seems to do in the Pentax K20D) then image read noise reduces even more so.

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John

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