Rune wrote:
>
> Photos are not subject to antialiasing I think.

Digital (sampled) photos are. To sample correctly a signal
the sampling frequency must be at least twice the maximum
signal frequency. The signal must be Low Pass Filtered before
sampling or the high frequncy components will be aliased or
mirrored around 0.5*sampling frequency and appear as low
frequency interference in the sampled signal. The term aliasing
comes from this. High frequency components appear as low
frequency components.

> But blurring has nothing to do with antialiasing.

In ccd cameras the obvious choice for LPF would be to defocus
the lens. This blurring limits the spatial frequency and
prevents aliasing. So blurring _is_ antialiasing and operates
on the unclipped signal. The blurred signal is then sampled and
clipped at the detector.


_____________
Kari Kivisalo

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