An apparatus, method, and other embodiments associated with performing interpolations to compute gain values that correct for varying spatial intensity are described. In one embodiment, a method includes determining, by an apparatus that processes image data, a gain value for a pixel in the image data for which there is no gain value available in the apparatus, by interpolating related gain values associated with corners of a rectangle bounding the pixel, wherein the interpolating includes determining at least two partial coefficients by interpolating pairs of the related gain values. Noise is filtered from the image data using a noise threshold, and the noise threshold is modified by using the at least two partial coefficients. The method also applies the gain value to the pixel in the image data.