VP400 Series Video Pro
Form7343A
Operation Manual
26
to judge the straightness of the lines.
The horizontal linearity control should be adjusted to make the pattern boxes all the same width.
The vertical linearity control should be adjusted to make the pattern boxes all the same height.
Pluge
Pattern Description
:
The Pluge pattern (
P
icture
L
ine-
U
p
G
enerator
E
quipment – BBC development) is arranged in
four concentric rectangular zones. The innermost rectangle is fixed at black (7.5 IRE for NTSC,
0 IRE for other formats) and has a five-step grayscale positioned on it. The second rectangular
zone from the center alternates between two light levels, black and slightly blacker than black
(7.5/0 IRE for NTSC, 0/-4 IRE for other formats). The third rectangular zone from the center is
fixed at a light level slightly whiter than black (10 IRE). The fourth, outer rectangular zone is
fixed at black. The average picture level (APL) of this pattern is very low.
Pattern Usage
:
Use this pattern to check the DC restoration (black
clamping) performance of a display device and to
set the picture black level with a low APL pattern.
A display device with less than perfect DC
restoration will exhibit alternating changes of
brightness in the outer two rectangular zones, due
to the display’s inability to perfectly clamp black
to a fixed level. This can be seen especially well
with the brightness (black level) control adjusted
to a slightly higher than normal setting. If the
brightness level of the outer two rectangular zones
remain constant as the second zone from the
center alternates between black and blacker than
black, the display has good DC restoration.
If a display has good DC restoration, its
brightness (black level) control can be
adjusted on either a low APL or high APL
pattern, with no change in black level as you
switch from one pattern to another. In that
case, this pattern makes it very easy to
accurately adjust the brightness control. With
the brightness (black level) control first
adjusted to a slightly higher than normal
setting, reduce the brightness control setting
until the brightness alternations in the second
rectangular zone from the center are just no
longer visible. The third rectangular zone
from the center should still be visible as
slightly whiter than black.
If a display device has less than perfect DC
restoration, you will need to decide, based on
the primary use of the display, whether the
black level should be adjusted on a pattern
with low APL or high APL. If the display will
usually be viewed in a darkened room, adjust
the brightness control with a low APL pattern,
such as this Pluge pattern. If the display will
usually be viewed in a bright room, adjust the
brightness control with the pluge levels in a
medium or high APL pattern, such as the
SMPTE Bar pattern or one of the Window
patterns set to a high IRE level.
