High Quality Content by WIKIPEDIA articles! Before the advent of photometers which accurately measure the brightness of astronomical objects, the apparent magnitude of an object was obtained by taking a picture of it with a camera. These images, made on photoemulsive film, were more sensitive to the blue end of the visual spectrum than the human eye or modern photometers. As a result, bluer stars have a lower (i.e. brighter) photographic magnitude than their modern visual magnitude, because they appear brighter on the photograph than they do to modern photometers. Conversely, redder stars have a higher (i.e. fainter) photographic magnitude than visual magnitude, because they appear dimmer. The symbol for apparent photographic magnitude is mpg and the symbol for absolute photographic magnitude is Mpg. The photographic magnitude scale is now considered obsolete.

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