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Author Topic: Lab color and noise reduction  (Read 10707 times)

Offline Hannie

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Lab color and noise reduction
« on: June 25, 2010, 10:08:21 AM »
I'm always trying to find ways to get rid of unwanted noise, stripes, dots etc.  in such a way that the photo doesn't deteriorate.

The image bolow is in bad shape and it has a lot of very fine white horizontal stripes.  The FFT filter did not work here because the white damage is not symmetrical.
All the different filters (noise, dust&scratches, reduce noise, median) I tried in various settings and the results always gave a substantial loss of detail.  Only when the settings were really low the image was preserved but then the damage would also still be too visible.

I remembered that sometimes the lab color mode is used for subtle adjustments to an image and I thought to try and use Lab color mode on this black and white photo I'm working on.

Firstly I flattened the image and changed the mode to lab color (I always work in RGB, even on B/W photos)
I clicked on channels in the layers palette and then I clicked on the Lightness channel.  I used the Reduce noise filter at strength 10. 
Convert back to RGB color mode and voila, no more white stripes and yet no signifcant loss of detail and I'm ready to restore the rest of the photo!

This method would probably work the same way in a color image.

Hannie



Hannie Scheltema
Distribution Coordinator
hannie@operationphotorescue.org

Offline glennab

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Re: Lab color and noise reduction
« Reply #1 on: June 25, 2010, 10:21:21 AM »
Hannie, that's really an impressive improvement. Worth remembering when facing that type of damage.  I check LAB once in a while trying to improve an image, but haven't had the luck (well, not really luck.  SKILL!) that you did with this one. Thanks for sharing the technique! 

Hugs

GK
What we do for ourselves dies with us. What we do for others and the world remains and is immortal. ~Albert Pine

(Photoshop CS5 /Mac Pro)

Offline Tori803

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Re: Lab color and noise reduction
« Reply #2 on: June 25, 2010, 01:09:03 PM »
Great tip, Hannie. Thanks!

Tori
Tori
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Online kiska

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Re: Lab color and noise reduction
« Reply #3 on: June 25, 2010, 02:54:13 PM »
Neato keano!
kiska
Photoshop 2021, MacPro

Offline Hannie

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Re: Lab color and noise reduction
« Reply #4 on: June 25, 2010, 03:10:01 PM »
Neato keano!

Kiska, I had to look that one up!  (David cracked up, he had not heard that expressions in years!)

Hannie
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Offline lurch

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Re: Lab color and noise reduction
« Reply #5 on: June 25, 2010, 03:38:50 PM »
Good tip!  I've often switched into Lab for noise reduction, but never for a black and white image. One of my favorite noise reduction techniques, especially before the new ACR and third-party Photoshop plugins got to be so effective, involved Lab. I'd convert to that color space and use median (or something like Noise Ninja) pretty aggressively on the a and b channels, then do noise reduction gently on the L channel.

Did you know you can make a smart object out of a Photoshop layer, double-click on it to get an editable .psb, and change the color mode of the .psb without affecting the mode of the original smart object?
<C>

Offline Candice

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Re: Lab color and noise reduction
« Reply #6 on: June 25, 2010, 07:19:16 PM »
I'm always trying to find ways to get rid of unwanted noise, stripes, dots etc.  in such a way that the photo doesn't deteriorate.

The image bolow is in bad shape and it has a lot of very fine white horizontal stripes.  The FFT filter did not work here because the white damage is not symmetrical.
All the different filters (noise, dust&scratches, reduce noise, median) I tried in various settings and the results always gave a substantial loss of detail.  Only when the settings were really low the image was preserved but then the damage would also still be too visible.

I remembered that sometimes the lab color mode is used for subtle adjustments to an image and I thought to try and use Lab color mode on this black and white photo I'm working on.

Firstly I flattened the image and changed the mode to lab color (I always work in RGB, even on B/W photos)
I clicked on channels in the layers palette and then I clicked on the Lightness channel.  I used the Reduce noise filter at strength 10. 
Convert back to RGB color mode and voila, no more white stripes and yet no signifcant loss of detail and I'm ready to restore the rest of the photo!

This method would probably work the same way in a color image.

Hannie





Great hint.  I just finished a picture with something like that.  It comes from the albums that use to have a sticky page backing.  I had several, as did many, growing up.

Thanks again.  I've just added it to my photoshop helps.   :up:
Candice

Offline Mhayes

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Re: Lab color and noise reduction
« Reply #7 on: June 26, 2010, 12:09:36 AM »
Hannie, thanks for the neat tip. Another way I have seen is to use the surface blur in LAB for the channel that has the most noise, which is usually the blue. Surface Blur is nice because at the lower end, it leaves the edges sharp.

I love seeing your before and after photo!

Margie
"carpe diem"

Margie Hayes
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Offline Hannie

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Re: Lab color and noise reduction
« Reply #8 on: June 26, 2010, 11:05:45 AM »
The white damage is not so visible in the original here.   The image I posted earlier is high res and shows the difference very well.
This photo is one of a series historical photos of the Volendam Museum, like the the AAMI and the GHF photos it is very important that detail and character of the photo remains the same.

I thought it was fun to post it anyways!

Hannie

Hannie Scheltema
Distribution Coordinator
hannie@operationphotorescue.org