IMAGE SIGNAL PROCESSING

Training apparatus for training a differentiable model of an image signal processor having a pipeline of separate image signal processing functions, includes processors configured to receive a reference image; and train a first differentiable module to perform a first image signal processing function, whilst not training other differentiable modules, by iteratively inputting, to the differentiable model a degraded image signal that represents a known degradation of the reference image, the degradation being related to the first image signal processing function; processing the degraded image signal using the differentiable model to produce a first processed image including using the first differentiable module to perform the first image signal processing function; calculating an error between the first processed image and the reference image; and updating the first image processing function performed by the first differentiable module based on the calculated error without updating the image processing functions performed by other differentiable modules of the differentiable model of the image signal processor.