More megapixels, better photos: Fact or fiction?

Started Feb 7, 2008 | Discussions thread
DRG Veteran Member • Posts: 5,217
Re: More megapixels, better photos: Fact or fiction?

Eric Fossum wrote:

No myth John, if I understand what you are saying correctly. Noise
has many components, including photon shot noise that goes like the
sqrt of the number of carriers, and readout noise, which is usually
fixed as a function of signal. We usually care about signal to noise
ratio, SNR. So for shot noise, S divided by sqrt (S) = sqrt(S). So
while the noise is less, when people say "noiseier" they are almost
always talking about SNR, which degrades with smaller pixel sizes for
the most part.

Did I understand you correctly?

Based on what John's written in prior posts, I believe he's concerned with the overall noise in the image (with the implication that any two images should be compared at the same output size) and not with the SNR on a per pixel basis. The ultimate basis for his argument is that a sensor that could enumerate the exact location of each and every photon hit would be capturing the maximum information possible in an image and that the output of any conventional finite pixel count sensor could be derived from that data and thus cannot exceed the quality of the data. So, more pixels equals better from an overall image point of view when comparing images at the same output size, on a hypothetical monitor (or other output medium) capable of displaying all the included information rather than resorting to downsampling. Oh, and with the additional assumption that the total photosensitive area is the same in all cases (that the electronics are somehow scaling to take up the same fraction of the pixel area).

I probably shouldn't be speaking for John but, hey, I have free wi-fi access in Starbucks and feel the need to take advantage of it

David

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