Digital Light & Color

Ref 1: DL-C Message Board thread, Chroma Noise Reduction: http://www.dl-c.com/board/viewtopic.php ... 23&start=0

Ref 2: Freeware "Ximagic Denoiser": http://www.ximagic.com/d_index.html

Ximagic Denoiser is a Photoshop plugin for image noise reduction.
It provides seven different methods for noise reduction:
--Median (Std/Center Weighted)
--Gauss (Std/Bilateral)
--DWT (Overcomplete Wavelets)
--CWT (Complex wavelets)
--DCT (Discrete cosine)
--NLM (Non Local Means)
--Non-linear (anisotropic) diffusion (Curvature & Gradient)
Support of 8/16 bits images.
Support of Photoshop actions/batch.
Support use as Smart filter.
Versions for 32 and 64 bit plugin hosts.
Mac and Windows versions.
Compatible with Paint Shop Pro, The Gimp, IrfanView, XnView, ...

I downloaded the "XiDenoiser MP v 4.4.1" (32 bit) file for use with Windows Vista32 and copied it into IrfanView4.33's "Image | Effects | Adobe 8BF filters..." folder.

Then using the image examples from Ref 1, the following results were obtained after several trials where the complete settings were not recorded:

Example 1: 1 pass [NLM-std denoise] Example 2: 2 passes [DCT-color denoise + NLM-std denoise] Not necessarily for the 'faint of heart' but the results look promising and the price is right [free].

As Irfanview4.33 is currently set for 8-bit [24 bit color] depth, the resulting noise reduced image versions are also 8-bit [24 bit color]...

...but they can be preferently blended in PWP's Composite-Blend transform where the Input is the original, noisy, 16-bit image and the Overlay is its 8-bit de-noised version... ...which with the Overlay Amount set to a preference and either Apply or OK clicked, will result in a preferentially blended 16-bit image de-noised version.

An Input image mask could also be used for specific image area and/or tone range blending control.

Thanks for the tip, Den. Now all I've got to do is remember it!

Mike.