An apparatus for combining multiple images to form a blended image, configured to identify regions of overlap: (i) in a first image and in a second image, corresponding to where those first and second images will overlap each other in the blended image; and (ii) in the first image and in a third image, corresponding to where those first and third images will overlap each other in the blended image, identify an image quality associated with each region of overlap, determine a gain for each image that, when applied to the image as a whole, will minimise a sum of: (i) a difference between the image qualities associated with the regions of overlap in the first and second images; and (ii) a difference between the image qualities associated with the regions of overlap in the first and third images and apply the respective gains to the first, second and third images.