1. A photographing unit comprising: an image pickup portion which outputs a first image pickup image obtained through photographing of an object; a display control portion which causes the first image pickup image from the image pickup portion and a second image pickup image from a different photographing unit to be displayed on an identical display screen, the different photographing unit being configured to photograph an image pickup range including an image pickup range of the first image pickup image; an image comparison portion which compares the first image pickup image with the second image pickup image; and an angle-of-view display portion which controls the display control portion on the basis of a comparison result from the image comparison portion to cause a frame image indicating the image pickup range of the first image pickup image to be displayed in the second image pickup image, wherein the angle-of-view display portion (1) sets a feature in a specific range within the first image pickup image as a judgment target image, (2) sets, in the second image pickup image, a judgment region identical in size to the judgment target image, (3) judges similarity by comparing the judgment target image with an image in the judgment region set, (4) moves the set judgment region and (5) repeats the act of judging similarity by comparing the judgment target image with an image in the moved judgment region, (6) changes a size of the judgment target image by scaling, up or down, the judgment target image, and (7) repeats the acts of setting a judgment region, judging similarity, moving the set judgment region and repeating the act of judging similarity using the changed size judgment target image.