Negative Materials (Monochrome, Continuous Tone). New York: United States of America Standards Institute. ASA PH2.12-1961. American Standard, General-Purpose Photographic Exposure Meters (photoelectric type). New York: American Standards Association. Superseded by ANSI PH3.49-1971. ASA Z38.2.2-1942. American Emergency Standard Photographic Exposure Computer. New York: American Standards Association. ASA Z38.2.6-1948. American Standard for General-Purpose Photographic Exposure Meters (Photoelectric Type). New York: American Standards Association. Superseded by ASA PH2.12-1957. ISO 2720:1974. General Purpose Photographic Exposure Meters (Photoelectric Type)—Guide to Product Specification. International Organization for Standardization. Japan Electronics and Information Technology Industries Association. 2002. JEITA CP-3451, Exchangeable image file format for digital still cameras: Exif Version 2.2 (PDF). Japan Electronics and Information Technology Industries Association. JEITA. See Japan Electronics and Information Technology Industries Association. Ray, Sidney F. 2000. Camera Exposure Determination. In The Manual of Photography: Photographic and Digital Imaging, 9th ed. Ed. Ralph E. Jacobson, Sidney F. Ray, Geoffrey G. Atteridge, and Norman R. Axford. Oxford: Focal Press. External links Doug Kerr's in-depth description of APEX Photographic techniques