I've been told that the point spread function of a pixel is its distribution of intensity, while the sampling aperture of a pixel is its distribution of sensitivity. I'm a little unsure of what the difference between intensity and sensitivity is. It sounds like the former deals with how a pixel is displayed, while the latter deals with how it is captured. Is that correct?
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Sounds correct to me. The point-spread function indicates how the intensity of a point source is spread among multiple pixels in an image. In an imaging sensor, the sampling aperture of a particular pixel indicates how it responds to intensity from points in space as a function of the spatial offset from the pixel's center.
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$\begingroup$ Just to confirm, when you say "how it responds to intensity", you mean, for example, if the sampling aperture followed a Gaussian distribution, the further away a point is from the center, the less intensity it will have? $\endgroup$– someguyApr 25 '12 at 13:52
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1$\begingroup$ Right. If there was a point source out in space, then the amount of intensity that the sensor would report for the pixel would follow a Gaussian curve as a function of the offset from the center of the pixel's field of view. $\endgroup$– Jason RApr 25 '12 at 14:13