Why doesn't my TV say 120Hz/240Hz?

A reader asks why his TV won't display 240 Hz. Geoff Morrison helps him out.

CNET reader Steven U. asks:

I bought a 240 Hz LED LCD, and if I press the "Info" button, all I ever see is 1080p/60. Does this mean I'm only getting 60 Hz? Is there something wrong with my TV? Do I need a special HDMI cable?
Your question is a pretty common one, actually.

So we're all on the same page, 1080p/60 stands for 1,920x1,080 resolution, at a frame rate of 60. 1,920 pixels across, by 1,080 vertically, all changing 60 times a second.

Other common resolution/frame rate combos are:

1080p24--24 frames per second, common with movies;
1080i--interlaced, as in 1,920 horizontal by 540 vertical, every 60th of a second. Nearly all cable/satellite boxes output this. Your TV combines the "half" frames (called "fields") into complete 1080p frames. Done correctly, you'll never know it was happening.

Check out What is 1080p24 and 1080i and 1080p are the same resolution for more on this.

The maximum resolution source you can get with pre-recorded material is Blu-ray. Most are movies (1080p/24), but some concert videos are 1080i/30. Also, some games on the PS3/Xbox 360 are output at 1080p/60, and you can do that resolution with a PC of course. To be clear, there is no such thing as a 120 or 240 Hz source. The TV industry is moving towards  higher resolution , not higher source framerates (for the foreseeable future).

With Blu-ray/gaming maxing out at 1080p/60, all you need is any high-speed HDMI cable to transmit that to your TV. Check out my article on Why all HDMI cables are the same for why you don't need an expensive HDMI cable.

Once that 1080p/60 gets to your TV, the TV converts that signal to 120 or 240 Hz. When you press the info button, you're getting the resolution of the incoming signal (i.e., 1080i or 1080p). The TV always displays, however, its native resolution and frame rate. In your case, this is 1080p/240. So no matter what you put into the TV, it converts it to 1080p refreshed 240 times per second. If you're curious about how refresh rate works, check out What is Refresh Rate and What is 600 Hz .

It's probably also worth it to check out my article on upconverting for more about native resolution.


Got a question for Geoff? First, check out all the other articles he's written on topics like why all HDMI cables are the same , LED LCD vs. plasma , active versus passive 3D , and more. Still have a question? Send him an e-mail! He won't tell you what TV to buy, but he might use your letter in a future article. You can also send him a message on Twitter @TechWriterGeoff or Google+.

About the author

Geoffrey Morrison is a freelance writer/photographer for CNET, Forbes, and TheWirecutter. He also writes for Sound&Vision magazine, HDGuru.com, and several others. He was Editor in Chief of Home Entertainment magazine and before that, Technical Editor of Home Theater magazine. He is NIST and ISF trained, and has a degree in Television/Radio from Ithaca College. His bestselling first novel, Undersea, is available in paperback and as an ebook on Amazon, B&N, and elsewhere.

 

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