Y Variable Gamma - Sony SS-HQ1 Application Notes

- SS-HQ1 Application Notes -
Ver.1.0.0 January 7, 2005

10.4.2. Y Variable Gamma

Any of the curves shown in Fig 10.4-2 "Y variable gamma" can be selected through combinations of
YGAMSEL and YKNEESEL (when GAMSEL=0[h]), or UYGAMSEL and UYKNEESEL (when GAMSEL=1[h]).
160%
YKNEESEL=5
WCLIP=6 (120%)
110 [%]
YKNEESEL=0
YGAMSEL=7
YGAMSEL=0
0
500 [mVp-p] 1000 [mVp-p]
(VRB)
AD INPUT ( VIN - VRB )
Fig 10.4-2 Y Variable Gamma
Note: The curves in Fig 10.4-2 "Y variable gamma" were created through software and do not represent actual
measurements.
When YKNEESEL (or UYKNEESEL) is selected with a value of 0[h] to 5[h], you can select from 48 different
curves. These curves represent a combination of eight different nonlinear areas, which are selected by setting
YGAMSEL (or UYGAMSEL) to a value in the range of 0[h] to 7[h], for the area up to AD input 500[mVp-p]
(125[%] of standard input); together with six different linear areas based on YKNEESEL (or UYKNEESEL) for
higher than AD input 500[mVp-p].
When YGAMSEL (or UYGAMSEL) is set to 4[h] or when YKNEESEL (or UYKNEESEL) is set to 3[h], the
gamma comes closes to 0.45 (inverse of standard CRT gamma value of 2.2), and the Y output is 100[%]
(equivalent to 100[IRE] for NTSC) with respect to AD input 400[mVp-p] (100[%] of standard input). With many
LCD monitors, the light emitting characteristics are such that gamma is greater than 1.0, but this is not a
standard value. Select the appropriate gamma curve for the monitor you will be using.
The maximum gamma output value is 160[%], but in the high luminance areas a white clipping process
(WCLIP, CAT2_Byte9_bit4-6) is applied in the last stage. (See the WCLIP=6[h] line in Fig 10.4-2 "Y variable
gamma".)
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