The Denoise filter in action

Denoise turned off:

Denoise turned on, using 25 frames for averaging:

Not only is this image much cleaner and its colors more stable, also the file size of this JPEG image is reduced by almost 50%, since the JPEG algorithm can work much more efficiently with a clean image. (It doesn't need to "reproduce" the noise.) As you can see, there is no blur added to the image. The filter simply circumvents a weakness in the stability of the CCD of the camera, which gives slighty different results at every pixel for each frame. By taking more of the same frame, and averaging every individual pixel, the resulting picture is much more stable, by actually eliminating the error in color measurements of the camera.