Most filter operations should be applied to the monochrome brightness rather than to the individual R, G, B color channels. That is not always the case for noise reduction filters, depending on whether the noise is different in the various channels (which in turn depends on where it originates and on the camera design). This interactive tutorial illustrates the effects of neighborhood averaging or Gaussian smoothing to random speckle noise.

The tutorial initializes with a randomly selected specimen image appearing in the Specimen Image window. The Choose A Specimen pull-down menu provides a selection of specimen images, in addition to the initial randomly chosen one. For a color image, clicking either the Monochrome Noise or the Channel Noise radio buttons determines whether the noise is added independently to each channel to the brightness values only. The Speckle Noise Level slider controls the amount of noise that is added. The Choose A Convolution Kernel pull-down menu determines the type of filtering operation that will be performed on the specimen image. The result of the filtering operation appears in the Filtered Image window.

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