An apparatus comprises receiver (101) receiving a light intensity image, confidence map, and image property map. A filter unit (103) is arranged to filter the image property map in response to the light intensity image and the confidence map. Specifically, for a first position, the filter unit (103) determines a combined neighborhood image property value in response to a weighted combination of neighborhood image property values in a neighborhood around the first position, the weight for a first neighborhood image property value at a second position being dependent on a confidence value for the first neighborhood image property value and a difference between light intensity values for the first position and for the second position; and determines a first filtered image property value for the first position as a combination of a first image property value at the first position in the image property map and the combined neighbor image property value.