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filmscanners: What causes this and is there any easy solution ?



Today I'm going for the dual prize of most boring picture (see attachment)
and most dumb question ever on the list.

Mark asked me about a problem in the background of some pictures
http://www.grafphoto.com/grain.html

The problem is that my sample (a bit of sky) from a slide projects with
perfect continuous tones at any size even 40 inch by 60 inch and it still
looks reasonably sharp (within reason)  but yet when I scan it at 4000dpi I
get a grainy effect that will show up in an A3 print and a soft image in
general. The problem often gets worse with sharpening . I have found that a
unsharp mask threshold 9+ usually avoids sharpening the graininess.
Alternatively a gaussian blur removes it but if you do this to the whole
image you end up with an even more soft image but on the plus side you can
sharpen it more aggressively and use a threshold of 3-4 which means much
more gets sharpened.

Obviously carefully selecting the sky/problem area and blurring that
separately is probably the best option but it takes ages to do this
accurately and you still may get noise problems elsewhere.

Am I right to assume the noise is grain, CCD noise and chemical faults on
the film ?

Does every see this noise ?

Should I see less with SS4000/A4000 scanner (is mine and Mark's a bit duff)
?

And what do you do about it ?

Steve

Attachment: grain.jpg
Description: JPEG image



 




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