CES 2009: Are they real? (I'm talking about 240 Hz LCDs, of course)

32S5100_med.jpgAre they real? Itâ''s the kind of question you expect to hear in Las Vegas, but not the question I thought Iâ''d be asking repeatedly as I checked out the latest LCD television technology at the Consumer Electronics Show (CES) in Las Vegas last week. The â''theyâ'' in question: the latest twist (ouch, bad pun) in LCD technology, the 240 Hz displays.

A little background. The digital television standard in the U.S. requires displays to put up a new image 60 times a second, or 60 Hz. That works just fine for technologies like cathode ray tube or plasma, in which a phosphor lights briefly whenever itâ''s called for in an image and then goes dark until needed again. Itâ''s not so good for LCD, because each pixel, once illuminated, stays on until the screen is rescanned with a new image; it doesnâ''t go dark in between scans. This doesnâ''t have any effect on still or slow-moving images, but for fast-moving images, the persistence of the pictures causes "motion blur". Motion blur can make pictures seem out of focus, or can make parts of an image seem to momentarily disappear. In sports, that disappearing part of the image is usually the fast moving ball, a real annoyance to fans.

LCD manufacturers figured out a few years ago that they could greatly reduce motion blur by increasing the rate at which new images are displayed on the screen to 120 Hz. Since theyâ''re only getting 60 images a second from the television transmission, they added processing power to the TV sets that generates additional frames by interpolating between existing frames. I looked at these 120 Hz sets at CES back in 2007 and was impressed by the difference, deciding this was one feature that would be worth paying extra for in my next television.

Of course, technology marches on, so it wasnâ''t a huge surprise to see announcements of 240 Hz LCD televisions at this Januaryâ''s CES. I found four such products on the show floor, but it turned out that just because a television is advertised at operating at 240 Hz, it might not be displaying 240 different images a second. LG and Toshiba are generating 120 images per second, but turning the LED backlighting on and off so each image appears and disappears twice, a virtual sort of 240 Hz. Sony and Samsung are interpolating three frames between each transmitted image, so generate 240 different frames per secondâ''real 240 Hz.

Is real 240 better than fake 240, and are any or all of the 240s better than the most recent generation of 120s? Iâ''d like to be able to give you a definitive answer, but the truth is, I just couldnâ''t tell. Each of the manufacturerâ''s lines were displayed at CES independently, so I had no chance of doing a side by side comparison, instead, I ran from booth to booth as fast as I could and back again, trying to hold the previous image quality in my mind. With this highly unscientific method, I couldn't detect a significant difference between virtual 240 and real 240.

And even in exhibits tuned by the individual manufacturers to present their 240 against 120 and 60 Hz models, demonstrations intended to show off the clarity of the 240, I had trouble identifying a significant difference between 240 and 120. I stood with other show attendees, squinting at the fast moving images racing across screens, getting slightly nauseous as I tried to figure out if the 240 was a bit more blurry than the 120. â''Look at the faces in the moving boat,â'' someone suggested. â''You can tell the faces are clearer.â'' Maybe. The only manufacturer that demonstrated an obvious difference between a 120 Hz and 240 Hz model was Samsung, and that difference seemed more due to a really blurry 120 Hz TV than any revolution in 240 Hz technology (the 120 Hz model was in a black box that obscured the brand information, so it may have been a very old model or a very cheap brand).

Pricing, on all of the 240 Hz displays introduced, was not announced, so itâ''s also not clear what the extra 120 Hz will cost, though fake 240 is likely to cost less than real 240. But, so far, Iâ''m not convinced either is worth any premium.

Advertisement

Tech Talk

IEEE Spectrum’s general technology blog, featuring news, analysis, and opinions about engineering, consumer electronics, and technology and society, from the editorial staff and freelance contributors.

Newsletter Sign Up

Sign up for the Tech Alert newsletter and receive ground-breaking technology and science news from IEEE Spectrum every Thursday.

Advertisement