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Scan Velocity Modulation

Posted by Joe Murphy Jr (A) on May 22, 2004 at 18:28:13

In Reply to: Re: Sony's Movie mode posted by AbeCollins on May 22, 2004 at 14:46:12:

From Video Essentials:

Scan Velocity Modulation (SVM) SVM is one of the many tricks manufacturers use to get more light out of a picture tube, at the cost of real picture detail. It changes the speed or velocity of the beam as it is scanned from the left to the right side of the picture. In the process, it distorts real picture detail, causing dark areas of the picture on light backgrounds to be reproduced much larger than normal and light areas on dark backgrounds to be reproduced much smaller than normal. When the beam spends more time "writing" light areas, the phosphors receive more energy and produce more light output. The fact that this will contribute to phosphor blooming, as well as detail distortion seems to be lost on a number of manufacturers calling it a "feature." <-- Next time you see a Best Buy ad with Mitsubishi displays, you might get a chuckle out of this. Though I suspect now that you know what it really is, like me, you may cringe instead.

The presence or absence of SVM can be easily detected by displaying the needle pulse test pattern. In it the width of the white line, on the black background, and black line, on the white background, are the same. In a set with SVM, the width of the black line will be much larger than the white line. The test pattern can be found in many places in Video Essentials. In particular we would point you at VE T17 C4.

If SVM is found on a set, look for an ability to shut it off. Several sets we've looked at provide this option in the mode of the set designed to accurately reproduce the signal source. In some other sets, it's easily defeated by a qualified service technician.

• http://www.videoessentials.com/glossary.htm#S   (Open in New Window)

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