In praise of AA filters

Started Oct 23, 2013 | Discussions thread
rovingtim
Veteran MemberPosts: 8,234
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Re: example
In reply to Lee Jay, Oct 25, 2013

Lee Jay wrote:

rovingtim wrote:

Lee Jay wrote:

rovingtim wrote:

This is a bird's folded wing surrounded by feathers. The bold diagonals should be plain, but a couple of them have become 'ropey' with a pattern that matches the feathers above them. Why?

That's the point - there's no way to know.

I'm agreeing with you here, Lee.

You can't recover aliased information.

No, but software can 'guess'.

It doesn't. It has no idea what information is aliased and what isn't, and it can't create data above Nyquist because there's no place to put it even if it had that data.

Nyquist is 2x the sampling frequency. On a sensor, that means a single pixel is undersampled. Thus the need for an AA. Take away the AA and print a dot for every pixel as if it has all the information and you are effectively imaging beyond Nyquist. So, if at 100% everything is crystal clear before you sharpen, then you know that what you are looking at is beyond Nyquist. I can list a number of cameras that do this.

How does the camera do this? I'm guessing software invention, but what would you say?

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