With this function you can remove single pixel phenomena, such as those that occur in the case of clocking induced charge with EMCCDs and as radio telegraph signal noise with CMOS sensors. It is a filter which analyzes the input image and removes pixels, whose intensity value diverges strongly from the median intensity of its neighboring pixels.

The filter analyzes the input image and removes pixels that are "much" larger than the median of their neighbors. The algorithm works as follows:

1. Sort all 9 pixels in a 3 x 3 neighborhood.
2. Determine the median intensity value of the sorted pixels.
3. Multiply the median by the threshold factor to get the limit.
4. If the center pixel intensity is larger than the limit, replace the pixel with the median.

Larger values of the threshold factor increase the value of the intensity limit and decrease the number of pixels that are replaced. The default value of 1.5 is arbitrary, but seems to remove charge induced noise from images acquired using cameras with EM gain capabilities. This filter can also be used to remove hot pixels from images.