Iconometer

An instrument with which to measure the size of or distance to an object by measuring its image (or icon). Sometimes an iconometer is a photographic viewfinder, separate from a camera.(pr. i:-KAH-nə-MEE-tər or I:-kə-NAH-mə-tər)An example of this last type: An iconometer, c. 1863. "It consists of a small lens, a camera, of the shape of an opera-glass, and a square focussing glass. By turning the lens towards the view it is represented reversed on the ground glass; and in this way the operator can judge whether his large camera will take in the whole or what portion of the required view." D?sir? van Monckhoven, A Popular Treatise on Photography. Translated By W.H. Thornthwaite. London, 1863. Quotation from Stanford University's Albumen site.Also see mechanical scale.