# Master bias frame

A master bias frame is created from a set of bias frame. The robust mean algorithm (chapter Robust mean) is applied on a pixel-by-pixel basis, while leaving out bad and overexposed pixels. If there are enough source frames, the robustness of the algorithm ensures that an accidental artifact is ruled out and does not affect the mean value. If a pixel has an invalid value on all source frames, it is marked as a bad pixel on the resulting frame.