LPHD
Topic Author
Posts: 8
Joined: Thu Aug 01, 2013 8:13 am

Color Noise Reduction? Help

Fri Nov 08, 2013 1:07 pm

Hi,

I need to reduce color noise for one of my shots to be accepted in the database.
The problem is that I've never used such a tool before. I usually use the usual noise reduction tools (with strength and detail preservation).

Do you know how to to do it? Do you how such a tool would be called in Gimp (that's the free software i'm using).
Thanks a lot in advance.

Cheers from France
 
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ghajdufi
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Joined: Tue Jun 14, 2005 5:18 am

RE: Color Noise Reduction? Help

Fri Nov 08, 2013 6:10 pm

Salut, I personally found the built in noise reduction in adobe camera raw and lightroom very very good. There is a slider for colour noise as well as for luminosity (?) noise removal. Of course if you are using Gimp this might not help you at all but perhaps you could try a free 30 day trial just to see what the software can do for this particular image you have.
I used to use Neat Image and Noise Ninja and I was quite happy with them too.
You could also send me the original and I can see what Lightroom can do with it.
Bonne journee,
HGabor
Your photos are like your children, you will always find them perfect.
 
ckw
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Joined: Fri Aug 27, 2010 12:26 am

RE: Color Noise Reduction? Help

Fri Nov 08, 2013 9:50 pm

There is a way to eliminate colour noise completely, but does not affect luminosity. I don't know Gimp but in PS a quick method is to apply a Gaussian blur to the whole image - no detail should be visible (a radius of around 2 - 3 should be fine).

Next, in PS its Edit -> Fade leave at 100% but select 'color' mode.

Perhaps someone familiar with both systems can translate this into Gimp.

Cheers,

Colin
Colin K. Work, Pixstel
 
mjgbtv
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Joined: Mon Jan 28, 2008 2:18 am

RE: Color Noise Reduction? Help

Fri Nov 08, 2013 10:01 pm

Quoting ckw (Reply 2):
Perhaps someone familiar with both systems can translate this into Gimp

It looks like the workflow and command names are pretty much the same in GIMP.

You could also use the G'MIC plugin for GIMP. It has a number of noise reduction modes for which you can select chroma noise channels.
 
LPHD
Topic Author
Posts: 8
Joined: Thu Aug 01, 2013 8:13 am

RE: Color Noise Reduction? Help

Mon Nov 11, 2013 4:36 pm

Hi,

Thank you very much for you help and answers. In the meantime I think I found a tool: it's called wavelet denoise. Have anyone ever heard of it?

I just uploaded my shot again to see if screeners accept it. If not, I'll get back to you.

Thanks again,
'god day
 
topgun3
Posts: 260
Joined: Mon Aug 22, 2005 6:27 am

RE: Color Noise Reduction? Help

Sun Nov 17, 2013 11:59 pm

I have to give a plug to DxO 9 Optics Pro. I just upgraded to it from version 7 and it has an amazing tool for de-noising any photo without loss of detail. It takes about 20x the usual length of time to process the photo (about 2-3min), but the results are worth it. The way it works is by comparing each pixel to the closest 1000 pixels to determine what colour it should be.
I'd rather be flying.
 
iamlucky13
Posts: 465
Joined: Wed Aug 08, 2007 12:35 pm

RE: Color Noise Reduction? Help

Mon Nov 18, 2013 7:12 pm

I use wavelet denoise and am happy with it considering it's a free plugin, although I haven't compared to any of the for-pay alternatives like Noise Ninja or the function included in Lightroom.

I've not tested it exhaustively, but I seem to get the best results when performing the noise reduction in YCbCr mode, which makes sense since this isolates the chroma channels from the luminance channel. I usually make a very small adjustment in the luminance channel to soften the graininess a bit, and about twice as large of an adjustment in each chroma channel to deal more aggressively with the more distracting color noise, plus a slight softness setting to avoid pulling out too much detail. For example:
Y - Threshold 0.5, Softness 0.2
Cb - Threshold 1, Softness 0.5
Cr - Threshold 1, Softness 0.5

That will result in a relatively light-handed noise reduction. Turn them up and fiddle as you see fit. You will lose more detail the higher you turn them up.

You will want to perform sharpening and resizing AFTER you do noise reduction. Fortunately, the results produced by wavelet denoise take an unsharp mask fairly gracefully.

Quoting ckw (Reply 2):
Next, in PS its Edit -> Fade leave at 100% but select 'color' mode.

Perhaps someone familiar with both systems can translate this into Gimp.

I believe in GIMP the feature is called Layer Mode (sometimes called blending mode), accessed in the layers window. You create a duplicate layer, apply your blur to one of them, then set the layer mode to determine how they blend together. I played around with a few different modes in GIMP just now as a test, but couldn't seem to get more than minimal reduction in noise unless I accept a big loss in sharpness. Wavelet Denoise definitely works better.

Selective Gaussian Blur (which only blurs features with less than specified value difference), works much better than what I was able to get with blending, but destroys fine textures making things look plastic, especially skin texture, hair, and foliage. Maybe you can combine it with ckw's blending method and see what you get, but from the trials I've done, Wavelet is still better.

Wavelet also wins over GIMP's native "despeckle" feature for the same reasons.

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