A spatiotemporal noise reduction system for compensating bias from image signal processing of raw video signals, comprising: an image signal processor comprising a spatial noise reduction filter adapted to output each pixel based on neighboring pixels in each raw video frame; a signal change detector adapted to receive the output of said image signal processor and a previous output frame thereby detecting any signal changes in each pixel; a signal combiner adapted to receive more than two input frames and therefrom generate a combination output frame, said more than two input frames comprising a raw signal frame, an output from said image signal processor, and a previous output frame of said spatiotemporal noise reduction system, characterised in that said signal combiner is adapted to output a convex combination of said more than two input frames; and further characterised in that the system comprises: a confidence updater adapted to determine a current confidence indicator for each pixel or block of pixels by updating a previous confidence indicator for a previous output frame of said spatiotemporal noise reduction system based on the detection of any signal changes received from said signal change detector; and a weight calculator adapted to calculate a convex combination weight for each pixel or block of pixels for each input frame of the convex combination based on said current confidence indicators. an image signal processor comprising a spatial noise reduction filter adapted to output each pixel based on neighboring pixels in each raw video frame; a signal change detector adapted to receive the output of said image signal processor and a previous output frame thereby detecting any signal changes in each pixel; a signal combiner adapted to receive more than two input frames and therefrom generate a combination output frame, said more than two input frames comprising a raw signal frame, an output from said image signal processor, and a previous output frame of said spatiotemporal noise reduction system, characterised in that said signal combiner is adapted to output a convex combination of said more than two input frames; and further characterised in that the system comprises: a confidence updater adapted to determine a current confidence indicator for each pixel or block of pixels by updating a previous confidence indicator for a previous output frame of said spatiotemporal noise reduction system based on the detection of any signal changes received from said signal change detector; and a weight calculator adapted to calculate a convex combination weight for each pixel or block of pixels for each input frame of the convex combination based on said current confidence indicators. a confidence updater adapted to determine a current confidence indicator for each pixel or block of pixels by updating a previous confidence indicator for a previous output frame of said spatiotemporal noise reduction system based on the detection of any signal changes received from said signal change detector; and a weight calculator adapted to calculate a convex combination weight for each pixel or block of pixels for each input frame of the convex combination based on said current confidence indicators.