An apparatus comprises a depth map source (109) providing a depth map for an image and a confidence map source (111) providing a confidence map with confidence values for pixels of the depth map. The confidence values designate the pixels as confident or non-confident pixels reflecting whether the depth value meets a reliability criterion or not. A depth modifier (113) performs a depth modification operation which modifies depth values for pixels of the depth map. A modified depth value for a first pixel is determined as a current depth value for the first pixel if this is designated as a confident pixel or if there are no confident pixels within a neighborhood set of pixels, and otherwise the modified value is determined as the maximum of the current depth value and a depth value determined as a function of depth values of pixels within the neighborhood set being designated as confident pixels.