Comparison of the pixel scales of Mars orbiters Comparison of the pixel scales of Mars orbiters Each square on the image represents the size of one pixel, or picture element, in each image. (This is not the same as the size of the entire image; each camera captures images that measure different numbers of pixels across.) The depth of the stack of squares represents the number of filters or channels in which the camera is capable of cpaturing images, a measure of its color-sensing ability. (By comparison, the human eye has three such channels.) Smaller squares, and taller stacks, are considered better than bigger squares and shorter stacks. Emily LakdawallaA PDF version of this diagram is also available.