HDTVs: Are More Hertz Worth More Money?
If you're shopping for a new HDTV this holiday season, you've likely seen higher refresh rates -- up to 240 hertz -- touted among the many bells and whistles that TV makers are offering on their flat panel sets. But before you whip out your credit card, we have a word of warning: extra hertz may not mean better picture quality.
Higher refresh rates are aimed at reducing the "motion blur" that can interfere with your HDTV's picture quality, particularly during fast-moving action in video games and sports events, for instance. In the past couple of years, refresh rates were bumped up to 120Hz, from the previous standard of 60Hz. Now, TV makers are offering sets with refresh rates of 240Hz.
Most experts and reviewers saw an improvement in picture quality with the jump to 120Hz. But the same is not necessarily true of the increase to 240Hz. While some experts do see differences with the newer 240-Hz rates, others disagree - and even those who do see a difference say it's not as marked as the difference between 120Hz and the earlier 60-Hz refresh rate.
PC World tackled this issue in a recent set of HDTV motion tests, which took into account the horizontal, vertical, and diagonal movements of images across the screen. The results? HDTVs whose LCD panels had at least a 120-Hz refresh rate generally did better than sets with a baseline rate of 60Hz. Yet the improvement from 120Hz to 240Hz was less dramatic.
In fact, some industry analysts argue that the differences between 120Hz and 240Hz are so small as to be undetectable to most folks. "From what I've seen, there is a change in picture quality from 60Hz to 120Hz. But the reason for moving from 120Hz to 240Hz just isn't there. The difference in picture quality reaches a level where it just isn't perceptible to the human eye," says Riddhi Patel, principal analyst for television systems at iSuppli.
According to Patel, manufacturers are targeting the 240-Hz refresh rate at consumers who've already bought their first HDTVs and are now looking at stepping to second generation products.
A higher refresh rate alone won't be enough to push consumers to replace their existing HDTVs, Patel contends. But people will end up adopting sets that offer 240Hz anyway when they buy new flat panel sets with more obvious advantages such as larger screen sizes, Internet connectivity, and LED backlighting.
"Moving to 240-Hz LCDs offers diminishing returns on quality - e.g. faster response to reduce motion blur - compared to the jump to 120Hz," concurs Alex Herrera, a senior analyst at Jon Peddie Research.
Herrera, however, does note one additional advantage to 240Hz. The higher refresh rate leaves the door open for 2 x 120Hz stereoscopic 3D, a still emerging feature "which many in the content and distribution businesses are hoping will be a market driver moving forward," according to the analyst.
"So if you're sold on stereoscopic 3D for your home entertainment, and you're willing to pay a premium while you wait for the rest of the stereo 3D-on-TV ecosystem to mature, then go for 240 Hz. If you're not sold on 3D, then it probably makes sense to wait until the premium comes down," Herrera says.
Meanwhile, researchers at DisplayMate Technologies have come up with test results showing "no detectable difference" in motion blur performance for LCD HDTVs regardless of their refresh rates - whether at 60Hz, 120Hz, or higher - their response times, or whether the HDTVs come with features such as strobed LED backlighting or motion enhancement processing.
"As a result, our bottom line recommendations are [that] if you stick with the mid- to top-tier models from the reputable brands, you should ignore response time specification, not worry about LCD motion blur, and [not] spending extra fro 120Hz or higher refresh rates, strobed LED backlighting, or advanced motion blur processing," says Raymond Soneira, president of DisplayMate.
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