at black (7.5 IRE for NTSC, 0 IRE for other formats) and has a
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.
Needle
Pattern Description: This pattern is black on top and white on bottom with lines (needle pulses) drawn from top to bottom on each side of the pattern, through the black/white transition. Electrically, the needle pulse lines are the same width on the top and the bottom of the pattern. A
Pattern Usage: This pattern makes it easy to detect whether scan velocity modulation (SVM) is enabled on a display device. If SVM is enabled, the black lines on the bottom of the pattern will be thicker than the white lines on the top of the pattern. It is also a good pattern for properly adjusting the contrast/picture/white level control for maximum white luminance level. If the
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