Just like every year, this years CES too brought along many innovations in smartphones, laptops, graphics cards and televisions. But one little feature that trickled down to laptops and caused a hoopla is the 240Hz refresh rate display demoed by HP and Asus.

So that got us thinking about why refresh rates matter and what's the difference they bring and while we were at it we even wanted to see what a display response time is and what effect it has on usability.

With 240Hz Display

HP's Omen 15, the first gaming laptop with a 240Hz display

Refresh Rate

The refresh rate is the number of times your display updates your screen with new information. The refresh rate is measured in hertz and needs constant feed from the video source to be able to display something at the specified refresh rate. Eg: A 60Hz display needs 60fps of the video that's being played back to match the fps and refresh rate. If the video source is limited to just 30fps on a 60Hz monitor, the display will just display a single frame twice to get around the lack of frames.  

If you look around you, your computer monitor, your phones display or your television all have a refresh rate of 60Hz but rarely do we use content that's 60fps. Movies projectors run at 24Hz with the movie itself being coded at 24fps. Videos on Youtube are 30fps (or 60fps) while some content maybe 48fps (The Hobbit movie) or 120fps (Slow-motion videos).

So why do we have so many different frame rates and refresh rates? It depends on the creator. A movie benefits from a slower frame rate like 24fps while some content like games need high frame rates like 120fps to allow you to savour the game.

Higher frame rates and refresh rate allows for a smoother motion to be seen in most content. Remember those old Nokia phones that could record video at 15fps and when you played back the film it would be jerky? Well, that is what higher frames rates and refresh rates aim to solve.  Modern smartphones like the One Plus 6T or the iPhone XS Max can record 4K at 60 fps which looks buttery smooth on their 60hz displays.
 

Screen TearingScreen Tearing

So now you may ask why then, do we need 120Hz displays and beyond that. The answer is an application. A higher refresh rate depends on what you are going to use the display for. Take gaming as an example, unlike videos and movies where the frame rate is set during the recording, games can output frame rates depending on your graphics cards abilities.

While an entry-level graphics solution may struggle to touch 30fps, a high-end one can cross 120 or even 200fps in some games. So what happens when you game on a 60Hz monitor with a graphics card that feeds it more than 60fps? the monitor ends up displaying more than 1 frame which causes a phenomenon called “Screen Tearing”.

screen tearing

An example of Screen tearing (Source)

Screen Tearing is when you see an image that is made up of more than one image as shown above. To prevent screen tearing on a fixed refresh rate monitor there is a technology called Vertical Sync (VSync) that caps the output of the graphics card to 60fps so that it complements the 60Hz refresh rate of the monitor.

That's all fine and dandy then right? Well, no. Putting a 60fps cap puts a load on your graphics card especially when it has to render high-end games which can cause frame drops when it's not able to render at the capped 60fps limit.

 FreeSync and GSync

To get over this we have two competing technologies that popular graphics card makers AMD and NVIDIA have released called FreeSync and GSync respectively. These two technologies work with dynamic refresh rate monitors which allows the monitor to vary its refresh rate based on the output frame rate from the graphics card.

How they work is, if your graphics card is outputting 30fps, the monitor refresh rate drops to that 30Hz and so on. The issue with this? You need compatible monitors and graphics cards which can add to your costs.
 

Fake Refresh Rates

So we now have monitors that go beyond the native 60Hz rating and the most common refresh rates for gaming monitors are 120Hz, 144Hz and 240Hz. The higher refresh rates allow a much smoother gaming experience especially in FPS games and while the benefits may not be always felt in they do make sense for gamers.

smoother gaming experience

Even smartphones today are trying to go beyond the 60Hz marks with the Razer phone pioneering the 120Hz SHARP IGZO display on the Razer Phone and Razer Phone 2. Asus too tried it with an AMOLED panel on their ROG Phone which could go up to 90Hz.

Android TV with WiFi connection

With High Refresh Rate being quite the rage in computer gaming monitors, manufacturers trip to replicate the same in television too but with a rather cunning approach. While games can be made to run at higher frame rates like 120fps and 240fps, the content that is streamed to television from satellite tv or movies is rarely above 24/30fps or 60fps.

Still, manufacturers promise refresh rates of 960Hz or 480Hz with snazzy names like TruMotion and Motionflow XR or UltraMotion and what not. The bottom line is these are faked and are really just simulated frame rates to make you feel the content is smooth but in reality that's not always the case.

To achieve that manufacturers the technological equivalent of a magic trick. One such trick is to insert black frames between the frames (Black frame insertion) to simulate the high frame rate or shutting down the backlight multiple times to achieve the same effect (Backlight Strobing).

Motion Interpolation

Motion Interpolation (Source)

The other more taxing solution involves using the onboard processor to work out intermediate frames to insert between the original 24 or 60 frames in order to simulate the high frame rate (Motion Interpolation) as shown with the bird above. While this does make the motion smoother it is often perceived as looking fake or soap opera like.

Extremely high rates like 960Hz or more as claimed by manufacturers are rarely achieved and are instead limited to 60Hz or 120Hz as found by Rtings who did an in-depth test to unmask these dubious Refresh Rate claims.
 

Response time

Response time

Response time is another factor that helps in monitors and televisions. Response time is defined as the time taken for a pixel to switch from one colour to another, usually black to white and is measured in milliseconds.

Why it is important is if you have a gaming monitor and you are displaying high frame rates at high refresh rates then you need your individual pixels to respond quickly to the data. Example: For a 60Hz monitor that is displaying 60fps, the maximum response time can be a maximum of 16ms (1 second/60 frames = 16ms to display one frame).

But you need the response times to be even faster as the pixel must be able to quickly display the next images or else you get to see “Ghosting”, a phenomenon where a part of the previous frame can be seen along with the next frame

That is why gaming monitors have a maximum of 8ms of response time (allows them to display 120 frames at 120Hz with a response time of 1/120 frames = 8ms per frame) which prevents ghosting and allows the pixels enough time to change the frame.  

Talking about response times OLED panels have a very low response time of about 0.01ms, while TN panels can go as low as 1ms and IPS can drop to 4ms although they are usually around 8ms. Wait for our next article to know the difference between OLED, IPS and TN panels.

Now the confusion caused by manufacturers is that they tend to report insanely low response times like 1ms on most monitors, despite there not being a standard way to measure response times. What they do is measure the time taken for a pixel to go from grey to grey which can be done quickly but going from black to white is what takes longer.

How do you get around this issue? Well, look online for reviews by experts who actually verify such claims to make sure you get what you paid for.


Verdict and Summary

To sum up, refresh rates and response times, remember that these are numbers and the first thing that you as a buyer must do is not to be swayed by numbers. Understand the applications of the technology. Are you going to use a monitor to just watch movies and browse Facebook then you probably don’t need anything more than 60Hz.

But on the other hand, if you want a smooth gaming experience at 120Hz with a gaming monitor makes sure your graphics card can handle the game at the graphics settings you wan and can actually provide the display with 120fps. Else you will have a 120Hz monitor that's being provided with only 60-80fps basically making it underperform.

Coming to response times for the average bloke it doesn’t really matter especially for televisions which are mostly 60Hz. Again where response time comes into the picture is for fast moving scenes mostly in games and that's where you need a monitor with a maximum of 8ms to allow for a ghosting free image.

Finally, do not forget that having a high refresh rate and low response time will not magically transform your gaming experience. There are many other factors from display resolution, quality of the panel itself and processing power of your computer and many other factors.

This sums up our third series on display standards and technologies do keep watching this space for more such insights on standards.  Also, don’t forget to checkout BlurBusters to see the visual differences between the different refresh rates.