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Sep 12

How do you decipher flat screen TV refresh rates?

LG 60LS5700 flat screen TV

What does the Refresh Rate stat do anyway?

When you start looking at TVs, one of the specs that is pushed hard is refresh rate. 60Hz, 120Hz, 240Hz. All of these are numerical descriptions of how fast the TV replaces a previous image with a new image?

But how does a TV go about doing this? How many different ways are used to create a refresh rate. And what are the benefits as you go up in refresh rates, and are there any dis-advantages to a faster refresh rate.

Plasma, DLP, LED TVs (oh my!)

We’re mostly going to focus mainly on LED/LCD style televisions, where these refresh rates have a direct correlation to frames per second. The “Hz” rating on Plasma and DLP TVs have a slightly different function that has more to do with picture quality than motion quality.

For Plasma TVs, 600Hz refers to how many times per frame the picture is processed. It looks at things like color, warmth, white balance, judder, and a few more things. Plasma TVs don’t use this to correct for frame-rate because there is no delay in how quickly it can change its picture between frames.

DLP TVs have a similar function, although in their case the 120Hz refers to a color processing mode that helps do spot corrections on the projected image. Again, frame-rate isn’t an issue because of the lack of delay in how the picture is displayed.

How your picture works

The standard image capture rate for TV and video is 30 frames per second. And in order to create fluid movement from these 30 frames, each image is doubled and “laced” together, creating 60 images for the 30 frames. It is the amount of laced images that are created that are measured in Hertrz. So your standard 30 fps with 60 laced images is 60 Hertz.

So when a TV states that it operates at 60 Hertz, it is a picture processing system, rather than a motion processor. As the refresh rate goes up, there has to be more images for the processor to process. So the 120Hz refresh rate necessitates the creation of additional images from the source to be uploaded to the processor. No longer are there 60 laced images, now there are 120 laced images, and they have been created by the processor to add depth and detail to the picture.

What about movies?

Ask any film buff, the small screen just can’t compete with the big screen. But as TV’s get bigger, will that ever happen?

Well, probably not, due to the fundamental difference between film and video. Film has been, since time immemorial, recorded at 24 frames per second. So how do you rectify 24 frames per second from film with 30 fps for video?

In order to create the necessary amount of images needed to convert film to video, the a process called 3:2 pulldown creates and adds a third video image to each second video frame, in order to “bulk up” the frame speed to a matching 30fps.

While this process has been around for years, if you ask a lot of people who love film you’ll hear about how the integrity of the movie experience is de-based by the additional images needed to move to the little screen. Which is why there is such intensity being caused by Peter Jackson’s new film, The Hobbit, which is being filmed in 48fps, and is raising it’s own controversy.

Every manufacturer has one

The manufacturers all have their proprietary methods of creating a faster refresh rate, with more natural color and movement. Sony has MotionFlow, Toshiba pushes ClearFrame, Samsung sports Auto Motion Plus. The list goes on, but they all are mostly similar.

All of these are based on the 60-120-240 HZ measurement that has defined the way we deliver images, and are combined with other processes as well, such as color correction, de-judder, and upscaling. This is similar to what Plasma flat screen TVs measure, but because there is no one standard for this particular spec between TV types, it’s still impossible to compare them on numbers alone.

Personally, I can’t say that I truly enjoy the higher refresh rates. When you line up a bunch of TV’s, (say, like on a sales floor at an electronics store- right down the hall) and start watching the different TV’s, I can say that sometimes the faster refresh rates look a little forced.

It’s not all bad, though. On some things (mainly sports) it looks a little more intense, which can be good.

What do you think about flat screen TV refresh rates? Do you love them? Hate them? Let us know in the comments.

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