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I am trying to perform some post-processing of Camera Raw images captrued using my Canon EOS 450-D. I am using PS CS5 and GIMP particulary to remove noise which is present in images.

My questions is:

In a typical image post processing, I think that most of the denoising happens almost always in the last step of processing in YCbCr data space. I am looking at some method/tool to perform denoising in Raw bayer data space itself on the sensor bayer data. Can you suggest any such tools, or algorithms/papers which talk about this? (I intend to implement my own denoising of bayer data eventually if I find some algorithm for it.)

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I've taken the liberty of removing the first part of your question, as it is exactly covered under What types of noise can be present in digital photographs? –  mattdm Jul 6 '11 at 14:41
    
@mattdm - ok. thanks. –  goldenmean Jul 6 '11 at 14:58

4 Answers 4

This is well beyond my understanding of the technology but I have read an article on this here. http://www.csie.ntu.edu.tw/~fuh/personal/NoiseReductioninRawDataDomain.A2-2-0103.pdf

It was an interesting read on the subject.

Also I notice you are using GIMP and CS5 for noise reduction, I found both to give me sub par results. I ended up settling on Nik Dfine for that process when I really need it and using Lightrooms built in noise filter as part of my process when I'm feeling lazy.

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Denoising is a vast subject, there are a lot of methods and a lot of research papers about it in the literature.

A simple and efficient algorithm that you can take a look at is called Non Local Means. Basically it aims at averaging pixels that look similar as there are a lot of redundancy in an image. You can do it on the bayer (by taking into account the pixels of the same bayer color) or on a demosaiced image.

Have a look here: http://youtu.be/9tUns4HYtcw

You can look for articles and demo on http://www.ipol.im/ also, which is a great source of image processing features.

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DxO 9 has a new PRIME algorithm that is marketed as being a very much improved noise reduction algorithm for high ISO images.

Here is a link to start you off on the PRIME algorithm. PRIME by DxO

I have used it myself and I am happy and quite impressed by the result. But it is very processor intensive and takes a long time to process each image.

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Check out RawTherapee's LMMSE demosaicing algorithm- it's designed for noisy images, and offers options on noise reduction.

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