What is the Refresh Rate for TVs

What is the Refresh Rate for TVs?

With values such as 12Hz, 240Hz and 600Hz, there is no wonder why refresh rate has recently attracted the attention in the marketing world of HDTVs. What is a refresh rate and how does it work?

Aside from knowing these basic things, understanding its existence is far more interesting. Why? Simply because its very existence can have an amazing impact on the picture quality of any HDTV.

Starting with the Basics

In the USA, electricity runs at a rate of 60Hz. With this basic information, it is just natural that televisions used here run at a similar rate. In other countries, 50Hz is somewhat common.

This basically means that newer models of HDTVs can show 60 images per second, or 60Hz. Just some few years ago, the introduction of LCD had taken the market by storm by using higher refresh rates.

The refresh rates started at 120Hz and now you can definitely see 240Hz and more. In this scenario, higher is better. However, in order to understand why it is better, it is important to discuss why it even exists.

For one, all LCDs often present a problem when it comes to motion resolution. This means that if there is an object in motion on the screen, the image can blur, as compared with an object that is just stationary.

During the earlier days of LCDs, this became predominant because of the so-called ‘response time’, or the speed in which the pixels can change from light to dark. The usual response on modern LCDs is considered to be quite good, and as such, this is no longer a big issue.

The real issue here is how our brain interprets actual motion. Since we are talking about individual brains, everybody is expected to see motion resolution quite differently.

This means that there are some people who may not even notice motion blur and are not even bothered with it.

On the other hand, there are some who can notice it right away and are deeply bothered by it. Others, still, know that motion blur exists, but do not consider it a major issue when it comes to picture quality.

How The Brain Interprets Motion and Blur

There are two general ways in which the brain can be fooled into seeing better quality in detail with the LCDS. One is backlight flashing, otherwise known as backlight scanning, and the other is frame insertion.

The first method, backlight flashing, goes dark in between video frames. That particular period of darkness works very similarly as to how a film projector also works.

First, an image, then comes darkness, repeating the process again. When this is slowly done, it may result in a flicker.

Another way is by performing a black-frame insertion – one which shows a black image between real frames.

However, this does not manipulate the backlight. However, with both 120 and 240Hz displays, another possible option is possible – frame insertion.

This is oftentimes called frame interpolation, creating completely new video frames that can be inserted between real video frames.

Modern Actual Refresh Rates

In the world of marketing, things can get more confusing. This is because different companies are focused towards promoting the actual refresh rate of their TVs.

However, some companies no longer state their refresh rates completely, providing alternative motion resolution ratings such as TruMotion, Clear Motion Rate and Motionflow XR.

In any case, companies use backlight scanning, and at times, couple it with extra processing in order to offer an implication that their TVs are equipped with higher and supposedly better refresh rates compared to what they can actually do.

For instance, a HDTV with a 120Hz Clear Motion Rate can actually be a 60Hz TV that comes with a scanning backlight, or it may simply be an LCD 120Hz but without a scanning backlight.

If you are searching for motion blur on your TV, it is very important to consider that in certain cases, the blur may come from the source. This is quite obvious with movies that are shot on film. Quick motion is expected to blur on film since it has a low frame rate.

Bottom Line

The refresh rate refers to the rate in which the TV screen displays a new image. Anything that is over 60Hz is a bonus, i.e. 120Hz or 240Hz.

All available modern video can either come in 24 frames per second (for most TV shows and movies, 60 fields per second, which is common among 1080i video), as well as 60 frames per second (7200 video).

If you are not too comfortable with the motion blur on your television screen, it would be better if you get the highest refresh rate LCD possible, or stick with OLED (or plasma).

Still, it may be worth mentioning that sometimes the processing which enables a high refresh rate may cause input lag on the system.

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