1、Rec. ITU-R BT.815-1 425 SPECIFICATION OF A SIGNAL FOR MEASUREMENT OF THE CONTRAST RATIO OF DISPLAYS (Question ITU-R 21 1/11) (1992-1994) The ITU Radiocommunication Assembly, considering that a reliable method to measure the contrast ratio of various displays is required; a) b) that the use of differ
2、ent signals can lead to different results; c) (APL) as close as possible to normal programme pictures, that the measurement of the contrast ratio should be carried out using a signal with an average picture level recommends 1. consistent measurement of contrast ratio. that the test signal and method
3、 of measurement shown in Annex 1 should be employed to facilitate the ANNEX 1 The test signai and method of measurement The test signal (see Fig. 1) consists of a peak white level patch surrounded by four black level patches, all set against a background of grey. The grey level of the waveform is at
4、 50% of the peak signal. The digital references to these levels are shown in Fig. 1. The luminance values of the peak white level patch, and of the four black level patches, are measured using a photometer. The ratio R of the luminance of the black level, to that of the peak white, is expressed in t
5、he following formula, the inverse of which is the contrast ratio: where: !&: measured luminance of peak white Lbl to Lb4 : measured luminance of black in the four areas. ITU-R RECMN*BT. 815-1 94 = 4855212 0521716 437 RW. ITU-R BT.815-1 41(603) 93(655) FIGURE 1 Signal for measuring the contrast ratio
6、 Black level (level 16) n Grey level (level 126) 1 920 samdes v1 c ?o - s 8 .- - vi 1- I 161(723) -c 265(828) 3 333(896) -c 506( 1 068) c U Black level Peak white (level 16) (level 235) no Black level (level 16) o Black level (level 16) o 1557(1 120) 1 II A 0 2Bttlx ( ) Indicates in 2nd field c*-cc Sample and line positions shown are for a 16:9 1125/60 system. Equivalent positions should be derived for other 16:9 and 4:3 systems.
