T number

noun Photography.
  1. one of a series of calibrations of lens openings according to the intensity of the light actually transmitted by the lens. Symbol: T
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British Dictionary definitions for t-number

T-number

T number

noun
  1. photog a function of the f-number of a camera lens that takes into account the amount of light actually transmitted by the lens

Word Origin for T-number

from T (otal Light Transmission) Number
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012