David's Take: What Your TV's Refresh Rate Means

David Susilo


Published: 04/19/2018 05:03:27 PM EST in David Susilo

David's Take: What Your TV's Refresh Rate Means

Just because your TV says it has a refresh rate of 120Hz or 240Hz, does that mean it's actually refreshing at 120Hz or 240Hz? Not necessarily. One of the latest techniques is using different technology to approximate the effect of a higher refresh rate, without actually driving the TV at the higher rate.

Confused? Read on.

Refresh Rate

Refresh rate is how often a TV "refreshes" or changes the image on screen. In a way, this is like the TV's "frame rate," though functionally, the two are bit different. A TV with a 60Hz refresh rate creates 60 individual images on screen each second.

All LCDs suffer from motion blur, where the image blurs or "smears" with motion. One way to combat this is with a higher refresh rate. The problem is that it's more expensive to make an LCD that refreshes at a higher rate, and "120Hz" and "240Hz" have been marketing gold for TV manufacturers. So in an effort to drive the numbers ever higher and include "higher refresh" in lower-priced TVs, manufacturers have gotten a bit, let's say, creative. But rightfully so.

Unlike contrast ratio, "fake" refresh numbers aren't complete fabrications. There's often a fairly simple method for determining each company's refresh rate claims. There are two primary methods for boosting the numbers beyond actually using a faster refresh panel.

The first is a scanning or flashing backlight. All LCDs use a backlight or edgelight to create the light used by the liquid crystal to create an image. Typically, this is always on, or at least cycling at the same 60Hz at which the rest of the TV runs. If the TV instead flashes this backlight rapidly, your eye would see the image, a moment of black, then the image again. It does this so fast that you don't see the flicker. Technically, you're seeing each frame of the image twice per second. This is a common practice, and can reduce motion blur.

The issue is calling it "120Hz" when it's really just a 60Hz TV with a scanning backlight causing you to see the same frame twice in a row.

Another method for potentially reducing motion blur slightly, but increasing the claimed refresh rate a lot, is video processing. Often this is "motion smoothing" which will create the dreaded "Soap Opera Effect," when the scenes look overly smooth as if the movie was shot using a camcorder.

Because so many TVs are marketed with a combination of the above either in addition to, or instead of, actually increasing the refresh rate, manufacturers don't want you to know what the actual refresh is. So here's what a few of them call their higher refresh tech, and what it really means.

LG TruMotion

The description for LG's TruMotion technology reads: "TruMotion increases the standard 60Hz refresh rate - how often the image is rendered on the TV screen - which drastically reduces blur and yields crisper details. It's a boon to all fast-action video, but most especially sports, so you won't miss a thing. LG TruMotion 120Hz, 240Hz, or 480Hz is available on select-model LCD TVs." TruMotion actually adds interpolated frame(s) in between the original movie frames to achieve the refresh rate as stated.

Panasonic

Panasonic is the most upfront about its backlight scanning: "120Hz, 1,200 Backlight Scanning Technology. Our advanced 1,200 Backlight Scanning technology employs fine light-emission control to minimize flicker and ensure smooth images without afterimage effects, even during high-speed action scenes in movies or sports programming." There's even an image to show what's going on. There's also "120Hz, 240 Backlight Blinking Technology. Panasonic's 120Hz/240 Backlight Blinking Technology delivers optimal sharpness, clarity, and contrast with virtually no image blur." There are a few other variations like this.

Samsung CMR

Though Samsung is fantastic at creative marketing ("LED" TV was its thing), it at least doesn't outright call the TVs with the aforementioned tricks "480Hz" refresh. Instead, it has "CMR" or Clear Motion Rate. "Samsung's more comprehensive Clear Motion Rate takes into account all three factors that contribute to motion clarity: panel refresh rate, image processor speed, and backlight technology." In other words, a TV with a CMR of 240 could be a 120Hz panel, with an average processor, and a scanning backlight, or a 60Hz panel, a fancy processor, and a scanning backlight. It's unlikely a TV with a CMR of 240 would be a 240Hz panel; as such an expensive panel would certainly come with one or both of the other features.

Sony MotionFlow

Sony's description gets a bit of an eyeroll for this one: "Motionflow XR 960 helps you see each end-over-end rotation [of the ball] by taking motion clarity beyond refresh rates, which are only measured in Hz, to quadruple the motion effect so you see everything as if you were there." This way, a 120Hz panel can have a Motionflow XR rate of beyond 1,000 Hz. Do note, however, Sony's frame creation is the absolute best on the market with the least amount of motion artefacts and the most natural looking video when applied. So in the end, who cares what they call it?

So what's the bottom line? Regardless of the numbers, the important thing is to see it for yourself. If you like it, that's the TV for you.





Article Tags:  refresh rate, television, 60hz,120hz, 240hz, motion, video, television

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David's Take: What Your TV's Refresh Rate Means








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