The Peak stereo magnifier is a simple device for viewing three-dimensional aerial photographs. These stereo magnifiers stand on two metal folding supports and are placed over the aerial photographs, which are spread out on a flat surface. The photographs can then be viewed with both eyes simultaneously through the two lenses. The coated lenses have a diameter of 32 mm. The 1994-2 version has 2x magnification and the 1994-4 version has 4x magnification. The lenses can be easily adjusted to the interpupillary distance. Usually, with overlapping photos, the pictures with the lower number are placed on the left and those with the higher number on the right. If this is not done correctly, a mountain, for example, will look like a valley. The two stereo magnifiers are also popular for judging images in stereo photography.