Saturation Color noise

[Reimar]

I am now struggling with a problem that I frequently encounter when manipulating images. I've got a nice clean image in which I want to increase the saturation. Even bumping saturation a modest amount (+20) results in grainy color noise.
What is the best method for increasing saturation without emphasizing the color noise?

[pmarchant]

Have you tried the Reduce Color Noise tool? Or if you used it earlier in your workflow, does using a higher radius help?

Cheers,
Paul.

[Reimar]

Yes I've tried the reduce color noise tool. I have not found that it solves the added large grain added when boosting saturation. Sometimes, in pictures that are too light, I can just add a layer set to multiply and reduce opacity until the picture is darkened and saturated to where I want.
But I came across a method that worked wonderfully for me in the already balanced picture I was having problems with. Here it is:
- Create a duplicate layer and boost saturation to +30
- Blur this layer with both a radial blur (@4Pix) and gaussian blur (@5Pix).
- Set this layer to color mode.
WOW!
This gave the strong color boost I was looking for, as well as a smooth finish.
I'm going to keep this in my toolbox and I'll be using it regularly.

[pmarchant]

I'm missing something here.

I don't see the point of the radial blur. Remove that and you've got the Reduce Color Noise tool!

Paul.

[Reimar]

I'm not sure why there is a difference, but there is. Even when I only use 5 pix Gaussian blur, but placing this blurred color mode over the whole image, I get a smoother finish than the Reduce Color Noise tool that blurs color over luminosity. Using the tool I still see globs of color patches. If I increase the radius very much I loose saturation, which was the point of the excercise.

By double bluring, I think the idea is to use a more linear blur to disrupt the color globs. A gaussian blur will tend to keep the globs intact unless the radius is quite high. But radial is not the blur I wanted (it gave great results around the edges where I was looking). I think I want a motion blur at around 10 pixs. Try it with a dramatic saturation boost and see if you can detect a difference.

[Richard_Lynch]

Reimar,

I would be interested to see the type of image that this is working on. Radial blur seems to me to be a sort of dangerous solution as it will clearly affect change in the parimeter of the image rather than the whole. The goal of using as little blur as possible is to retain semblance of original color...If you are having color 'gobs' I would both look into the source of the trouble and see if blurring of specific channels may not be a better answer.

ON THE OTHER HAND...I checked your method by working both, side-by-side on the same image, simply following your instructions with one and adding a saturation layer to my technique. After the images were complete and flattened, I dragged one into the other (holding shift) and set the mode of the upper layer to Difference. There barely was one. When I flattened and enhanced the result (with a levels correction) the changes were more pronounced around the parimeter (exactly what might be expected) AND the greatest difference was shown in areas where solid blocks of color met -- appearing as color bleeding or undesireable color distortion, if you will.

Certainly if you are interested in increasing saturation, you should do so. However, I don't know that Radial blur is the best choice. If you are working with the reduce color noise tool, run the tool, step back one step in the Undo, and add a saturation adjustment to the color layer. It will save some fiddling, and should prove less destructive.

Paul, again -- good call.