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[filmscanners] Re: Grain aliasing: Thoughts, solutions?



You are correct.  Once the errors have been incorporated into the file
data, it takes some much bigger crayons to hide them. ;-)

Art

George Hartzell wrote:

> Tony Sleep writes:
>  > [...]
>  > With all aliasing the easy cure is to degrade the frequency of image
>  > information so that it falls well within the Nyquist limit.
>  > Defocussing, or
>  > antialiasing filters, do the job. I presume software that attempts to
>  > deal
>  > with it relies on some sort of blur function, which is how you can
>  > attempt
>  > to deal with it in PS. It could be clever and only act on areas where
>  > aliasing occurs, but there is no way to deal with aliasing and retain
>  > the
>  > HF info that causes it. Aliasing is just an inescapable property of
>  > pixels.
>  > [...]
>
> I think that it can make a big difference between whether you degrade
> the frequency of the image before/while it's scanned (e.g. defocusing
> the scanner) or whether you try to blur in photoshop.
>
> When you do it as part of the scan, you just have to throw away enough
> information to get within the Nyquist limit.
>
> Once you've collected aliased data though, the problems are usually
> much larger blobs and you have to blur the daylights out of them to
> get them to go away.  You end up throwing away much larger details (is
> a large detail like a jumbo shrimp?).
>
> g.
>
>


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