Originally Posted by Michael Gerald-Yamasaki
Roger,
I tend to think of noise as being an error in light measurement, specific to a pixel (rather than generic like light drop off from a lens). .......
I don't think there is a universally satisfying solution for this conundrum nor do I think the new camera releases will expose the myth (which ever one it is)... I'm inclined to think that there are a sufficient number of variables between the sensor and discriminating output to render a definitive answer incalculable.
Hi Michael,
While one can consider the noise we see in our digital camera images an error in measurement, most of the noise we see is due to the light itself, not the lens sensor and electronics recording the light.
Photons arrive at random times and we are counting photons for a relatively short interval (the exposure time in a camera). The noise is the square root of the number of photons collected. This is the dominant noise source (light itself) that we see in our images. The electronics in digital cameras add a small amount of noise but it usually only becomes a factor in the deepest shadows. It includes read noise from the sensor, and noise from the electronics including fixed pattern noise (FPN). But on any subject you photograph (excluding very long (minutes) exposure astrophotos), the main noise you see in images is due to photons. The photon noise is quite predictable and so is sensor read noise and other electronic noise. So the response of a camera is quite predictable. It is mostlly basic physics and engineering.
What is no predictable is how people react to noise sources. Different people seem to tolerate noise in images differently. One observation I find interesting is as digital cameras were emerging, people didn't like the images because they were "too smooth." People wanted that film grain as they thought images should look that way. Now people complain about the tiniest amount of noise.
Roger
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