Re: Deconvolution of Sensor Anti-Alias filter?

[A complimentary Cc of this posting was sent to
Dave Martindale
<davem@xxxxxxxxx>], who wrote in article <dhao16$pm6$1@xxxxxxxxxxxxxxx>:
> >> I've been told that manufacturers treat this is a tunable parameter. If
> >> the spread is exactly one pixel pitch, you get a null in the response of
> >> the system right at the Nyquist frequency, which is theoretically good.

> >I do not see how this may be "theoretically good". There is no
> >aliasing at the Nyquist frequency, it appears *above* Nyquist. So
> >having a zero at Nyquist has absolutely no point.

> More precisely (though you really ought to know this):

[Irrelevant argument omitted; see discussion in another subthread.]

Actually, I think I found an easier argument to convince you that an
AAF which has its first zero at Nyquist frequency (in other words, which
shift the image by exactly 1 pixel) is absolutely useless. I hope it
is a much more convincing argument than calculating cosine at some
random points. ;-)

Here it is:

The effect of AAF which shifts the image by width of 1 pixel can be
*completely* reconstructed by postprocessing the digital image (just
shift the digital image by 1 pixel, and average).

As everyone knows, no aliasing can be removed by post-processing.
Ergo: such a "filter" *does not remove any aliasing*.

Is it more convincing now?

Hope this helps,
Ilya
.

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