Display Standard - Veritas et Visus

Veritas et Visus Display Standard February 2009
Motion smear: Motion smear is a well known issue with LCDs. It arises because the liquid crystal is unable to
change its orientation rapidly enough when the picture changes. While all of the LCDs clearly show smear with
moving DisplayMate test patterns and video containing computer generated scrolling text (which is functionally
similar to a moving test pattern), it is very hard (even for a trained observer) to spot smear in real video content that
isn't actually in the source. When people see motion blur, it is generally in the source content and not the display,
but they blame the display...
We’ve done extensive testing in side-by-side simultaneous comparisons on all 11 units using an HD-TiVo with
many hours of recorded sports with lots of fast motion and camera panning. We have a reference Sony CRT
monitor (which has zero motion smear and artifacts) and a reference plasma (which has zero smear and barely
detectable digital motion artifacts) as control displays. If we think we see smear on one unit we press the 8-second
Tivo backup button and watch the sequence over and over again on all of the units (LCD, CRT, Plasma) until we
understand what is happening. There is smear but you have to study the displays and carefully search for it before
you find an occasional real event in real video. Note that scrolling text almost always involves sharp transitions
between high to low or low to high intensities. That is where the response times are the fastest and also where the
signal processing that reduces blur, including higher refresh rates, is the most effective. On the other hand, most
video content involves complex images with softer gray-to-gray transitions, where the response times are inherently
longer, where the signal processing is not as effective, and where human vision simply doesn't notice the blurring
elements in the overall picture. We have evaluated 60Hz CCFL units (Sony, Samsung, LG), 120Hz CCFL
interpolating units (Sony and Sharp), and 60Hz strobed LED units (Samsung) and it is very rare to see motion
smear on any of the LCDs that doesn’t smear on the CRT and plasma. This indicates the smear is in the source
content. More importantly, there is very little visual difference between the 60Hz, 120Hz, and LED strobed units.
Test patterns show differences in blur and artifacts, but with real video, even with multiple instant replays to study
differences in a large selection of fast moving content, there is very little noticeable difference between the units.
LCD response time: LCD motion smear is generally evaluated with a response time specification. Unfortunately,
just like the viewing angle specification, it is not particularly relevant because it measures the time it takes for a
pixel to go from black to white and then back to black again. However, most picture transitions involve much
smaller and more subtle gray-to-gray transitions, which take a lot longer to complete. As a result the LCD display
with the fastest response time specification frequently does not have the smallest visual smear. As a result, it
appears that the 120Hz units, the upcoming 240Hz units, and the pulsed LED LCDs are primarily for marketing
rather than picture quality improvements, in effect marketing gimmicks. Consumers will be drawn to the advanced
panels because they appear to have better specs, even though the actual observable differences from the 60Hz units
are small or undetectable for most picture content.
Screen photos from the viewing tests: These screen photographs demonstrate the change in color with viewing
angle for each of the test units. When viewed in person the differences are much more pronounced than they appear
here in these printed thumbnails.
Panasonic - PDP Sony – LCD
Red door –on-axis color is good, but shifts to orange in off-angle Sony LCD Photograph Don Cochran
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