Tuesday, November 27, 2007

Simple Noise Removal - use the Color Replacement Tool

Welcome back to our incredibly noisy image. Today we'll look at a semi-destructive way to remove colour noise. I say semi-destructive because even though we are using a "painting tool," the content and context remains unchanged. Working from a layer copy and hiding the original, we're simply removing the noise in this image the easy way.

Introduced in Photoshop CS, the Color Replacement tool can be used to remove digital noise from images. Paint away noise? Yes. Colour noise ... those red, blue, and green specks in our images. Noise is common in low light situations, like our noisy image. But noise can happen in any image.

Let's take a look at this simple technique.

Start with the Eyedropper tool. In the Options Bar, set the tool to sample a five-pixel by five-pixel area. Click in the area that you'll be fixing to select that color as the foreground color. We're starting with the red masonry and then moving to the dirty white marble. Every time you move to an area with a different major colour, use the Eyedropper tool to select that colour.

Once you've selected your work area and your colour, select the Color Replacement tool. In the Options Bar, set Sampling to Continuous, Limits to Find Edges, and a Tolerance of about 30%. Then simply paint away the noise. Notice how the detail and luminosity is preserved as you paint away the noise.

Click on each picture to compare the before and after shots. In ours, that orangy yellow noise is gone from the white marble and the blue noise is gone from the red areas. We've also managed to get rid of the noise in the roll-up doors' sill. Try this one for yourself and watch the noise melt away.

Enjoy the day.

1 comment:

Anonymous said...

Here is another example of how to remove color noise. this is quite a good technique to know.