B&K Precision 1253 - Manual - Manual (Page 9)

2: PLUGE
(Picture Line Up Generator Equipment)
Description: The Pluge pattern (Picture Line-Up Generator Equipment – 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 gray scale 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/-5
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.
Examples of Uncalibrated Displays: The following image indicates a TV with the Brightness set too
high, because flashing rectangle is visible. Adjust the brightness down until the flashing just disappears.
Flashing Inner Rectangle
should not be visible