Middle gray

50% lightness in Lab color space

In photography, painting, and other visual arts, middle gray or middle grey is a tone that is perceptually about half way between black and white on a lightness scale;^[1] in photography, it is typically defined as 18% reflectance in visible light.^[2]

Middle gray is the universal measurement standard in photographic cameras. To calibrate light meters, whether in a camera or hand held, the 18% gray card was conceived. It is assumed that the measurement taken by a meter gives the exposure for a shot so that some of the light reflected by the object measured is equivalent to middle gray.^[3] However, many note that modern cameras generally treat 12-13% gray as "middle gray".

In the sRGB color space, middle gray is equivalent to 46.6% brightness.^[4] In 24-bit color, this is rounded to RGB value (119,119,119) or #777777.^[5]

History

In the Zone System of Ansel Adams, middle gray is known as "Zone V" in the scale of 11 zones from Zone 0 (black) to Zone X (white).^[6]

As early as 1903, middle gray was defined as the geometric mean intensity between a white and a black intensity that are in a ratio of 60:1.^[7] That is equivalent to 12.9% of the white intensity.

References

1. ^ Stephen Quiller (1999). Painter's Guide to Color: Includes the New Quiller Color Wheel. Watson-Guptill. ISBN 0823039137. http://books.google.com/books?id=unHoFlKMHTAC&pg=PA36&dq=%22middle+gray%22&lr=&as_brr=3&ei=_pJ_SOOOM4WGtgORovDhDw&sig=ACfU3U1bTgJ6Fa8XGWwS5ggPSZm1cR60Dw. 
2. ^ Blain Brown (2002). Cinematography: Theory and Practice : Imagemaking for Cinematographers, Directors, and Videographers. Focal Press. ISBN 0240805003. http://books.google.com/books?id=1JL2jFbNPNAC&pg=PA121&dq=%22middle+gray%22+18%25&lr=&as_brr=3&ei=T5R_SLvJLY32sgOQpPThDw&sig=ACfU3U0HBWvLxWkRp3dT74Tzdb9HEdgt_Q. 
3. ^ Steven Barclay (1999). The Motion Picture Image: From Film to Digital. Focal Press. ISBN 0240803906. http://books.google.com/books?id=9qRzglF7GsYC&pg=PA38&dq=%22middle+gray%22+18%25+gray-card+calibrating&lr=&as_brr=3&ei=DJV_SJcIg_SxA57c4boI&sig=ACfU3U2KI3yWWt02WsrUXlD0vH4rcJ98rg. 
4. ^ http://www.cdiny.com/ArticlesWhitePapers/ISO%20Standards%20for%20Museum%20Imaging_cdi_v1.0.pdf
5. ^ http://www.brucelindbloom.com/index.html?ColorCalculator.html
6. ^ Jonathan Spaulding (1998). Ansel Adams and the American Landscape: A Biography. University of California Press. ISBN 0520216636. http://books.google.com/books?id=gYrwnAL8nYMC&pg=RA1-PA172&dq=%22middle+gray%22+ansel+adams&lr=&as_brr=3&ei=i5V_SMPkFIfctAPC4uy0CA&sig=ACfU3U2OJuiu7C43SBl5AQKmKhCELyyNGw. 
7. ^ Daniel Coit Gilman, Harry Thurston Peck, and Frank Moore Colby (1903). The New International Encyclopædia. Dodd, Mead and Company. http://books.google.com/books?id=aV1MAAAAMAAJ&pg=PA128&dq=middle-gray&lr=&as_brr=1&ei=jSqASL3oDaOGtgO55_zhDw. 

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