[Tig] How to lessen a grainy shot that was underexposed?

glenn chan glennchan
Mon May 8 15:13:35 BST 2006


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Thanks to oktobor for supporting the TIG
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I've tried Noise Ninja on an image sequence, and it does work very well.
Like many noise removal plug-ins, it's slow.  I believe it would be faster
if it were an After Effects plug-in (After Effects does filters much faster
than in Photoshop from the poking around I've done).  After Effects 6.5 and
up have a "remove grain" filter, which I believe is based on Grain Surgery-
there's a photoshop version of it.  There are comparisons out there between
Noise Ninja, Grain Surgery, and Neatimage.  If applying s-shaped curves, it
may be better to apply the filter post-processing.
All of these filters will be *slow*.

For Final Cut, there is Graeme Nattress' DVNR, which is priced very
inexpensively ($30USD).
http://www.nattress.com/Products/set1/GDVNR.htm
I haven't used it myself, but there is a watermarked demo.  I suspect it's
not as good quality... temporal NR tends to produce motion artifacts.

And if it's really bad, add some artistic diffusion.  (Hey, I'm only
half-kidding here!)

2- In the future, it seems to me that the way to go is to use optical flow
to improve temporal noise reduction.  This should reduce the amount of
motion artifacts in the image.  There will still be areas where the oflow
algorithm will be uncertain... this is where motion artifacts would crop
up.  In that case, the filter should be smart enough to apply spatial noise
reduction instead (i.e. noise ninja, neat image, etc. are all spatial).

If you want to see really good spatial denoising, see
http://www.greyc.ensicaen.fr/~dtschump/greycstoration/demonstration.html

Glenn
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