One of the many confusing aspects of buying a new TV is trying to understand the technical specifications that the TV manufacturers tell us.
One of the most common ones is the TV refresh rate. We get told this TV has a refresh rate of 120 Hz. 240 Hz. 480 Hz. More!
So, which is the best refresh rate for a TV? The bigger number is better right? Well, not as much as you might think. And, in many cases, not at all.
So, let us try to understand the refresh rates of LED and OLED TVs, and answer some of the most common questions. It is a complex subject, and I’m not a scientist. But, I’ll try to explain the most important points in words I can understand. Hopefully, you will too.
The refresh rate of a TV is the number of times per second the picture is 'redrawn'. Or, to put it another way, how many images it can show in one second.
The quicker a picture is refreshed, then it should help any motion to appear smoother to the human eye - and to have less flicker. This is a good thing.
First up, it’s a good idea to understand the difference between the frame rate of a video recording and the refresh rate of your TV. They are two different things but influence each other.
As you probably know, video recordings capture live action by taking a series of still images – or frames. If these frames are close enough together in time, then we will see this as smooth motion when played back.
Historically, the frame rate of analog video was based on the frequency of the local power supply. This means that it was different around the world:
Incidentally, content recorded on film is traditionally recorded at 24 fps.
To save bandwidth during transmission, analog video was always interlaced. This means that a single frame was divided into two fields containing the odd numbered lines and the even numbered lines of the image. The TV screen would then display these fields in the correct order to play the video.
Therefore, in PAL regions, the frequency of interlaced video was 50 Hertz (Hz):
In NTSC regions, the frequency of interlaced video was 60 Hertz:
By the way, Hertz is a standard for describing the frequency of something i.e. the number of cycles per second. It can be used to describe the frequency of anything, not just video frame rates.
Due to these standard frame rates, TVs used a refresh rate to match the frequency of the transmissions. So, TVs in PAL regions had a 50 Hz refresh rate, and TVs in NTSC regions had a 60 Hz refresh rate.
Now, these frame rates were developed for analog TV systems. Even so, they've remained the standard even with the new digital broadcasting systems - ATSC in the US and DVB in Europe.
Modern broadcast video standards support a few different frame rates. The most common are:
The frame rate is sometimes added to the end of the picture resolution to describe the frame rate used:
The higher frame rate will display smoother motion as there are more frames to capture it. This is what determines how smooth the motion will appear on your TV – not the TV refresh rate.
So, now we understand that the standard refresh rate of TVs is either 50 Hz or 60 Hz, why do we see different TV refresh rates quoted when we go to buy a new TV?
You can see quoted refresh rates of 120 Hz, 240 Hz, 480 Hz and more.
To begin with, you should understand that the maximum native refresh rate of a modern flat screen TV today is 120 Hz. This means it can display 120 images every second. So, if you are looking for the TV with the highest refresh rate, the answer is that most of them are the same as each other.
Anything higher than this is marketing hype designed to make you buy a ‘better’ TV. The bigger number must be better, right? I’ll discuss these higher refresh rates later.
So, is a 120 Hz TV better than a 60 Hz TV? The obvious conclusion is that a TV with a 120 Hz refresh rate will display a smoother image. However, it's not as simple as that.
We also need to consider the frequency of the content that is going to be displayed on the TV. And, we now know that the frame rate of the content, and the refresh rate of the TV, are two different things.
If we take a video recorded at 60p, then to display this image on a 120 Hz TV, each frame is repeated twice – 60 fps x 2 = 120 fps.
For a 30p video, we just repeat the same frames 4 times – 30 fps x 4 = 120 fps.
However, this makes no difference to how smooth the image looks. There is no increase in detail of the movement. Your 120 Hz TV is just showing you the same frames that you would see on a 60 Hz TV.
Also, when you input a 60 Hz video, some 120 Hz TVs will just switch to a 60 Hz refresh rate. So, again, no difference to a standard 60 Hz TV.
So, does this mean that there is no point in buying a 120 Hz TV? No, I wouldn’t go that far, but it does mean that the benefits are not going to be as great as you might think.
The main benefits of a 120 Hz TV are:
So, while there are some benefits of a 120 Hz TV, you may not find many of them that useful in your day-to-day viewing.
Now, if you are buying a new TV, you may not have a choice what you get anyway. The refresh rate on a 4K TV will often be 120 Hz. Even though some will claim to have more! Cheaper models may only be 60 Hz.
In the guide to the best OLED and LED flat screen TVs in 2018, I include the refresh rates of the featured models.
So, how do we explain the higher refresh rates of 240 Hz and above?
You might see a TV advertised with a refresh rate of 240 Hz. Good, huh? No, because it isn’t.
A refresh rate of 480 Hz? Wow, that sounds great! Except, it isn’t really.
As mentioned previously, there are currently only two actual refresh rates for TVs in the US. 60 Hz and 120 Hz. These are native refresh rates i.e. the rate at which the TV can actually refresh the screen.
Anything else you see is marketing smoke and mirrors released by the manufacturer to make their TV more appealing.
These ‘increased’ refresh rates are just inflated numbers that can only be realized by the TV processing the picture. Each manufacturer has their own name for this processing:
Each of these is used to claim a refresh rate higher than the actual figure for the TV. Which makes it very difficult to compare like-with-like.
For example, with Samsung, a motion rate of 120 for a 4K TV will have a native refresh rate of 60 Hz. A 4K Samsung TV with a motion rate of 240 will have a native refresh rate of 120 Hz. As you can see, unless you are aware of this, it can be difficult to understand the motion rate vs the refresh rate.
There are a few different ways that TV manufacturers try and achieve smoother motion. The most common are motion interpolation and black frame insertion/backlight scanning. It is these processing techniques which are used to justify claims of higher refresh rates.
The idea behind motion interpolation is that we can increase the frame rate of a video source by adding extra frames. Frames that don’t exist in the actual recording.
Therefore, to make a 60 Hz video playback at 120 Hz (or more), we can enable motion interpolation in the display menu of the TV.
Each manufacturer will call this something different, but the idea is the same. Motion interpolation creates extra frames by making an educated guess where the movement between two frames will go. Effectively taking two consecutive frames and creating an extra one in the middle.
So, if the frames of a 60 Hz video go from this to this:
Then the motion interpolation will add an extra frame in the middle. The result is the motion will look smoother because there is less of a jump from one frame to the next:
The trick to making this work effectively is how well the interpolation algorithm performs the task. While this can work well for some fast-moving images like sports, many people don’t like it. It can create an image which looks very unnatural -especially if used with movies. This look is often called the ‘soap opera effect’.
It is also not recommended for use with gaming as the required processing can introduce lag. This is fine for watching TV, but it makes gaming difficult.
If you are unsure, just switch it on in the menu of your TV and see what it looks like. You can always turn it off again!
These techniques are used on some TVs to improve motion. They are not directly connected to the refresh rate of a TV, but they can be more effective on a TV with a higher 120 Hz refresh rate.
Backlight scanning and black-frame insertion are essentially the same processes. They are called different things by some manufacturers. The idea is that by turning the screen black in between each frame of a video, we can fool the eye into seeing smoother motion.
This works because motion blur is caused in part by the pixels of the TV screen not switching color quickly enough. With TVs, they use a process called sample and hold which results in the pixels holding on to their color for a fixed period. The human eye can see this as a blurring of the image in fast-moving pictures.
One solution to this problem is to make the screen black in-between frames. This makes the color transition of the pixels much sharper and cleaner.
Anyway, the details on how it works are less important. You just need to know that some people think it can be quite effective. And others can’t stand it.
These features are usually enabled and disabled in the menu settings for the TV. Try it out and see what you think.
I have mentioned motion blur a couple of times already, so I think it’s a good idea to explain what this is.
I think it’s important to mention this in an article on refresh rates. Many people get confused between television refresh rates and the motion blur that they see on screen. They assume that a high refresh rate will remove motion blur. It can help, but it’s not the solution.
Don’t forget, the frame rate of the source material is a major factor in seeing smooth motion. Progressive video recorded at 60 fps will look smoother than that recorded at 30 fps because it captures more detail in movement. Motion blur is something different.
Motion blur on a TV occurs where the image appears to go blurry when there is quick movement on the screen. This is especially noticeable with sports content.
It is a misunderstood issue because the motion blur that you see is caused by several different factors:
All of these contribute to what people see as motion blur. As you can see, none of these are directly caused by a low refresh rate.
In a modern TV panel, there are a couple of ways to try and fix the effect of motion blur. They are our old friends - motion interpolation and backlight scanning. We have discussed these already further up the page. While higher refresh rates can help to make these techniques more effective, they are just a small part of the whole problem of TV motion blur reduction.
Motion blur on a TV can be very annoying. However, some people are more sensitive to it than others.
So, what have we learned from all this technical mumbo jumbo?
Unfortunately, I’ve written a lot of words just to tell you that the refresh rate of your TV isn’t that important. Maybe I should have just said that in the first place and saved us all a lot of time!
The main take away is that the quoted refresh rate of a TV should be taken with a pinch of salt. If it says anything higher than 120 Hz, then that isn’t the real native refresh rate.
Even when you have the right numbers, there aren’t too many instances where the increased refresh rate will make a huge difference to your daily use.
If you like delving into the menu and changing a few settings, then you may get an improved performance in some circumstances. However, many people don’t like the look of the processing modes that you can enable, and so don’t use them.
In many cases, you will buy a TV based on your budget. The more expensive models will likely be 120 Hz, and the cheaper ones 60 Hz. Simple. Just don’t get too hung up on the higher numbers.