The Dust & Scratches filter works on single color spots and incorporates the entire digital image. Dust & Scratches filters remove surrounding spots or lines and then fills the hole in between with new colors.
Figure 5.66 demonstrates the use of the Radial Filter tool (Filter ^ Tools > Radial Filter ) where the red outline is the original image. The line is smaller than the Radius value, and each of the lines crossed by the line is different from its neighbors.
Figure 5.67 shows the dust and scratch filter in action. Note that the image was scanned from color print, and the scan was processed to remove all color and color artifacts. The filter works by replacing the pixel data that sits above, below, left, and right of the dust and scratch artifact. Note also that the filter uses the entire digital image as data to work on.
There are a number of settings that can be made for the dust and scratch filter. The following paragraphs provide information about this filter. Figure 5.68 shows how the Dust & Scratches filter looks when the Radius value is increased from 3 (original) to 3.5, 4, 5,..., and 8 pixels. The larger the Radius value is: the more the outer region of the dust and scratches is obscured, which makes them harder to distinguish. You can apply the filter in different ways by pressing the equation button and scrolling through the controls on the left of the dialog box or by clicking the dialog box's OK button.
Figure 5.69 shows how the Threshold control affects the filter. If the Threshold value is set too high, you can get away with a less-than-perfect image. However, if the Threshold value is set too low, you can get away with an image of poor quality.