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Smoothing on LCDs--Ask the Editors

CNET editors address reader mail asking about smoothness witnessed on LCD TVs.

Pioneer's 2007 plasmas have a de-judder mode. CNET

Hi David,

Based on my price range and the reviews I've read, including yours, I'm very interested in the Samsung PN50A550 and the Panasonic TH-PZ85U series. However, when I went to see them in the shop, I was very impressed with the video quality of the Sony KDL-XBR4 and the Samsung LN-T4671F. The first two are plasmas and the second two are LCDs, but I was most impressed with the smoothness of the latter two. You commented on that smoothness in your reviews and made it seem like it's a feature that can be turned on/off. Anyhow, I was just wondering if that feature is available in the plasmas I was interested in. You seemed to comment how it can be unnerving at times and it seems like a feature than can be adjusted. There isn't much of a mention of it in the Samsung A550 review and I just wanted to know if that smoothness can be turned off/on in the plasmas. Thanks, Jon

Hi Jon,

That smoothness I mentioned in my reviews is the result of a de-judder video processing mode. Pioneer put a similar mode on its 2007 plasmas, including the PDP-5080HD (pictured), but it's not as smoothing and it introduces a lot more artifacts compared with the LCDs I've tested, so we preferred to leave it turned off. More recent reviews of de-judder-equipped LCDs include the Samsung LN52A650 and LG 47LG60. To answer your original question, I don't know of any plasma TVs available now aside from Pioneer's models that have de-judder processing.

De-judder is designed to do just what you observed: smooth out motion. Film and video are captured as a series of still frames at a certain fixed rate, typically 24 and 30 frames per second (fps), respectively. That rate has a big impact on how motion--particularly movement of the camera such as when it pans across a scene, pushes forward, pulls back, or zooms in or out--is perceived by the viewer. The film rate of 24 fps can introduce stuttering in fast motion or pans, but usually this stutter is fast enough that people don't notice it, much like a cartoon flipbook that depends on your brain to do the work of creating the perception of motion. This stuttering is generically called "judder," and it's often exaggerated by the 2:3 pull-down processing required to translate that 24-frame source into the 60Hz refresh rate used by HDTVs, including most LCDs and plasmas.

When a de-judder mode is engaged, the TV's processor kicks in and interpolates extra frames between the ones that actually exist. Imagine the processor drawing extra pages (in real time!) in the flipbook, as many as four extra for every original page, to bridge the visual gap between the true frames that were originally captured. What you see is more information in the moving video, which you interpret as more smoothness. Americans are used to seeing film at a rate of 24 frames per second, and when we see it instead at 60 or 120 fps, it can seem unnatural and too smooth--in short, too much like video or, as its advocates might say, real life. In a side-by-side display, such as what you saw in the store, that difference in smoothness, between a TV with no de-judder processing and one that has it, can be drastic indeed. Whether that extra smoothness actually improves the experience of watching the film is a matter of debate; personally, I don't think it does, but some people, yourself included, seem to like it.

For information on how de-judder relates to 120Hz TVs, check out Fully Equipped.

-- David