Who cares about 120Hz TVs?

TV manufacturers are now marketing a new feature-higher refresh rates. Not sure what that means? Let’s break it down.

Until recently, all TVs in the U.S. had a refresh rate of 60Hz. This means that every one second, your TV turns all of it’s pixels off and on a total of 60 time-hence 60 Hz. The new fangled 120Hz TVs fire up all of their pixels 120 times every second. And the 240Hz TVs do this 240 times a second. “So what,” right? Does it really matter?

Let’s start at the beginning, American TV is broadcast at 30 frames per second. When broadcast TV was first created, engineers decided that 1 frame of video was too big to transport in just one trip.

The solution was to break each frame in half and broadcast each half-frame (a.k.a. “field”) twice as fast. This process is called interlacing.

You don’t need to know this, it helps to know that that are two different types of interlacing I can tell you that it comes in two flavors:
1. Progressive Segmented Frame (or PsF if you’re in the “biz”) An example of progressive segmented frame would be video that was converted from film. With film there is no interlacing, each frame has only one field. With PsF video,  one field is simply cut in half and then turned into two fileds. The viewer still only sees half of each frame at a time but because this happens so fast it looks very much like progressive video.
2. Standard Issue Interlacing (my name for it) Instead of starting with one full-sized image, this version, starts with two images at half resolution. It annoys me that this process is still called “30 frames per second” because the viewer sees 60 unique images every second. The effect is much less cinematic then progressive video.

Okay, back to refresh rates. Picture a train. Trains can’t fit all of their cargo into just one car, so cargo is divided up over several train cars.

Video does the same thing; one frame can’t be be broadcast within a 30th of a second so each frame is broken in half and then broadcast twice as fast.

American video plays at 60 fields per second, which means that TVs need to put a new picture on the screen 60 times every second otherwise known as having a 60Hz refresh rate.

So what’s the deal with the fancy new 120Hz TVs? Its my understanding that this is all because of 3DTVs. 3DTVs basically have to show two videos at the same time (RIGHT EYE and LEFT EYE) so that the screen will need to refresh twice as fast (60Hz RIGHT + 60Hz LEFT =120Hz 3D). My theory is that once engineers figured out how to do that they wanted to slip that technology into all TVs whether it was essential or not.

These 120HzTVs do a few neat things that standard 60Hz TVs do not, such as:
1. Reduced flicker and eye strain. This is not something that will necessarily impress your friends but it does make a more pleasant viewing experience. You may have noticed on some LCD TVs that when going from a bright scene to a dark scene it takes a second for the screen to fully adjust. It can make a hard edit look more like a dissolve. 120Hz TVs fix this problem.
2. Supports true 24 frames per second playback. Most blu-rays are encoded at 24 frames per second to preserve the motion quality of film and standard 60Hz TVs have to modify that frame rate in order to be able to play. 120 is divisible by 24 so 24 frames per second video can play without blending frames. If you’re not a real stickler for video then this feature might not blow you out of your seat but it makes me feel legit.
3. Simulated higher frame rates. Modern TVs are starting to act more like computers. Once this higher refresh rate was figured out, engineers decided to teach the TVs computer to simulate more frames per second. The TVs computer can look at two adjacent frames of video and guess what a frame between the two of them might look like. It isn’t perfect, but the idea is that it will happen so fast that less than 100% accuracy will do. This is the one feature of these TVs that is extremely noticeable. Personally, I hate this feature. It makes video look like fast motion. It’s especially annoying when watching movies. The movie industry has made such efforts to make HD look like film, and this effect completely undoes a lot of that. Personally I don’t care about hurting the movie industry’s feelings; I just don’t like how it looks. It might be cool for video games though. Try it out and see what you think.

So, in conclusion, 120Hz vs 240Hz? It’s the same thing, only 240Hz is an even higher refresh rate. Most people are perfectly happy with their 60Hz TVs so I imagine that there is little perceivable difference between 120Hz and 240Hz TVs.

This new TV feature is yet another example of how Americans are out of real problems, but go buy one anyway-we did!