Extron Electronics VTG 400D_400 DVI User Guide - Manual (Page 79)

A-15 VTG 400D/400 DVI • Appendix
19. Checkerboard
The checkerboard consists of sixteen rectangles with half being black
(0%) and half being white (100%). This pattern is commonly used to
measure contrast ratio of the display system and is the prescribed
pattern for performing contrast ratio measurement within the ANSI procedure.
Fundamentally, contrast ratio is the ratio of the peak white luminance value divided
by the minimum luminance value near black. By mathematical definition, as the
black level approaches true zero light output, contrast ratio approaches infinity.
This pattern may be used to perform the ANSI contrast ratio measurement regimen
or other methods as well. The user may “invert” the pattern which will change the
luminance of the starting rectangle and subsequent rectangles from the original
luminance level to the opposite level. Distortion of the 100% white rectangles on a
CRT-based or plasma type display indicate a condition of overdrive.
20. Bounce (automatic)
Some operating conditions of displays may only be evaluated or
perceived with moving images or images that change in average duty
cycle (picture content) over time. The APL (Average Picture Level)
bounce pattern provides just such a test. The central area is comprised
of a large white rectangle with a black crosshair pattern. The pattern automatically
changes between full white and full black continuously at one-second intervals.
This duty cycle shift assists evaluation of black level shift. For CRT-based displays,
high voltage regulation performance may be evaluated. High voltage variations
with image duty cycle changes cause one or more combinations of distortion among
the components of the pattern such as the white rectangle, the lines within the
white rectangle, or the lines surrounding the pattern.
21. Bounce (manual toggle)
This version of the APL (Average Picture Level) bounce is static and
may be exercised by the user at will. Use the Invert function on the
VTG’s soft keys to cause the pattern to invert, or shift, at any moment
desired. This capability is used when evaluation under conditions of
random performance is desired. See the automatic version of the APL bounce
pattern for more information.
1 sec.
1 sec.
Bounce Pattern
The white box in the center of the pattern toggles between black and white once every
second. The border on the outside of the pattern does not change .