Photo Restoration - - Reducing Noise Through LAB

KR1156 · #1 02-06-2006, 02:45 PM

Hey, does anyone know any good tips on reducing noise in an image through LAB color space?

I have a few HR jpegs that need to be rezed up over 250 %......just curious if anyone knew how to tone down the artifacts and noise without blurring or losing image detail and quality.

Thanks.

Jeronimas · #2 02-06-2006, 02:56 PM

Quote:

Originally Posted by KR1156

Hey, does anyone know any...

I think this should help you
http://www.dgrin.com/showthread.php?t=20907

mistermonday · #3 02-06-2006, 08:07 PM

If you have an image that does not have noticeable noise, it won't be noisy when you upsize it particularly if you use a high quality setting in PS or a specialized plug-in like genuine fractals.
As for noise reduction, you can get rid of color noise in LAB by blurring the A & B channels. However, if you have noise in the L channel, that won't help you much.
PS-CS2 has some good noise reduction filters. There are also great noise reduction applications / plugins like Neat Image (free), Noise Ninja, and a ton of others.
Regards, Murray

KR1156 · #4 02-06-2006, 09:46 PM

Thanks alot guys, for the link and the feedback. Appreciate it.

The images I'm working with already have heavy noise, so I tried to reduce it as best as possible by blurring the A & B channel but the L channel was pretty noisy, so i didn't really fix much. I don't have much experience with LAB so I am just looking to learn a little more about it. I heard it has a lot of advantages over RBG/CMYK.

Thanks.

mistermonday · #5 02-06-2006, 10:42 PM

If you would like some suggestions on your noise problem, why don't you upload a sample and you can get some feedback specific to your noise problem.
Regards, Murray

byRo · #6 02-07-2006, 04:23 AM

Just a reminder. Usually a straight Gaussian blur of the A and B channels will end up causing the colours to "run".

If using CS then the surface blur will do the job better.
If in PS7, you can try the Noise>Median filter.

Another thought...
Although I'm the first to agree that LAB is great for a lot of stuff, that doesn't mean it's always the best path to take.
Your original image was probably in RGB, did you look at these channels first?
It's usually a pretty good bet that the Blue channel will be the noisiest and, luckily, this is one channel with which you can be pretty heavy-handed.
Try denoising (Neat Image / Suface Blur / Median) this first.

Rô

imann08 · #7 02-07-2006, 11:07 AM

What byRho says is a must I think. Always look at the RGB channels first before going to LAB if that's where you want to go to mak your fixes. I do think that fixing the blur in LAB is better because you aren't messing with contrast while you do it. RGB is much better to find out where these problems exist though because the channels are more defined than the blurred color channels of LAB. That's how I see it.