1. An image processing apparatus comprising: image input means for inputting an image that includes a person's head; photographing-position information input means for inputting photographing-position information of a camera that photographs the image, the photographing-position information being attached to the image input by the image input means, the photographing-position information input means being able to input four values, one of which is attached to the input image, the four values being a) a first value indicating that no significant photographing-position information is inputted, b) a second value indicating that an upright posture of the image is to be recognized as an upright position of the image, c) a third value indicating that a horizontally-oriented image with the person's head at the right is to be recognized as an upright position of the image and d) a fourth value indicating that a horizontally-oriented image with the person's head at the left is to be recognized as an upright position of the image; face-detection angle-range information determination means for determining a first angle range used in a process of detecting a face from the input image when the value attached to the input image is the first value, a second angle range used in a process of detecting a face from the input image when the value attached to the input image is the second value, a third angle range used in a process of detecting a face from the input image when the value attached to the input image is the third value, and a fourth angle range used in a process of detecting a face from the input image when the value attached to the input image is the fourth value, wherein the first, second, third, and fourth angle ranges are different from each other, wherein the first angle range is broader than the second, third, and fourth angle ranges; and process control means having a mode to control the execution of the face detecting process on the basis of the determined angle range determined by the face-detection angle-range information determination means.