What is the Refresh Rate?
The refresh rate is the number of frames per second the television can display. Its unit is a Hertz, which is equal to 1/second. 120Hz means it can draw 120 images per second. The refresh rate of televisions is a bit misleading and is mixed with a few marketing gimmicks. The increased refresh rate (120Hz and higher) was introduced by manufacturers as an indirect way to find a solution to the motion blur problem of LCDs and LEDs. You will see a motion blur if the image moves faster than what the screen can draw. LCD panels in the last few years have become really good at reducing the motion blur. The best measure of motion blur is to calculate the time a pixel takes to transition from one color to another, also known as the response time. If that time is less than the time between the images, no motion blur will be seen because there is no overlap. There is no simple and consistent way of measuring that time; it depends on a lot of factors like the preceding colors.
Manufacturers came up with a great marketing idea: instead of drawing only 60 frames per seconds, lets draw 120 frames. This will give the customer the impression that television can draw images twice as fast, thus reducing the motion blur and making the television more fluid. However, this does not guarantee the absence of overlaps between those images. In fact, the real transition time of the pixels mostly stayed the same. Additionally, manufacturers are inflating the advertised refresh rate number by adding, for example, the backlight scan rate like in Samsung's Clear Motion Rate.
A real advantage of a 120Hz and higher refresh rate is to properly display 24p movies.
What is a good refresh rate?
As said above, the Refresh Rate is mostly a marketing gimmick. While the 120Hz alone is not worth it, it usually come with a better panel, which could have a better response time and produce a better image.
|Panel refresh rate||60 Hz||120Hz||240Hz +|
|Normal TV or Passive 3D||Ok||Good||Good|
|With Active Shutter 3D||Invalid||Ok||Good|
We recommend the upgrade from 60Hz to 120Hz, but not more. If possible, you should go see it in person if you can notice the difference. However, if you are watching 3D with the Active Shutter technology, you will need 240Hz to achieve the same result because each eye receives only half the frames. You will also see less flickering if you are using Active Shutter at that speed. You cannot have a refresh rate of 60Hz with Active Shutter 3D, because that will mean a per eye refresh rate of 30Hz, which is really bad.
What is Samsung Clear Motion Rate?
The Clear Motion Rate (CMR) is a made-up number invented by Samsung to qualify how a TV can reduce the appearance of motion blur. The refresh rate alone is not a perfect representation of the motion blur, so they added on top of it the backlight and processor speed.
While it is true that the refresh rate is not the best representation of the motion blur, Samsung is misleading the customers because it usually only displays the CMR in its specifications instead of the real panel refresh rate. This inflated number makes the comparison across brands harder to do.
Clear Motion Rate
Clear Motion Rate, TruMotion and MotionFlow to Refresh Rate conversion
The table above converts Samsung's Clear Motion Rate (CMR) into the real panel refresh rate, so you can better compare it to televisions of other brands. The upgrade from a 240 CMR to 480 is not worth it, because it is still the same actual panel refresh rate of 120 Hz. Conjointly, televisions with a Clear Motion Rate of 720, 840 and 960 all have the same real refresh rate of 240 Hz.
Does the refresh rate mean the same thing for a LCD, LED and Plasma?
A Plasma screen has a higher refresh rate because of how it works, so the refresh rate comparison is more important in a LCD/LED screen. You will see a lot less motion blur on a Plasma TV than on a LCD or LED, where you can see some on the lower end models.
What is motion interpolation?
Motion interpolation is a common feature on most 120Hz and higher televisions. Most media are recorded either at 24 frames per second or 30 fps. Originally, a 120Hz television would display the same frame multiple times before switching it to the next frame to have the end result of displaying only 24 or 30 frames a second. The television refresh rate is a lot overkill in that situation, so the manufacturers added a technology that creates new frames in between the original frames. Samsung calls this interpolation technology Auto Motion Plus, for Sony it is Motion Flow and LG, TruMotion. These new fake frames are an interpolation of the movement of the picture, making the television footage looks a lot more fluid.
Most people will appreciate the increased fluidity. However, the motion interpolation has 3 main downsides.
- Cinematographic purist complains that it kills the film experience and it is against the movie look, creating a video that looks so real it becomes unrealistic. This is called the Soap Opera Effect.
- The interpolated frames could contain errors or distortion because they were generated by a computer which is not the same as if the camera was really capturing those frames.
- The processing takes some times to execute, which could increase the input lag, making it not suitable for gaming.
What is the Soap Opera Effect?
When watching a movie (who are traditionally filmed at 24 frames per second) with the motion interpolation feature on, it will look a lot more smooth to the eye. This is called the Soap Opera Effect, because it looks similar to how the soap opera shows looked, having been shot with a 30fps camera instead of the standard 24fps one. Some people do like the increased fluidity, but it is not for everyone. The motion interpolation feature can be turned off in the settings menu on all televisions, if you are annoyed by the Soap Opera Effect.
What is 24p Playback?
24p playback means the television can produce exactly the full 24 frames per second, a feature only found on higher refresh rate TVs. Movies are usually filmed in 24 frames per second as shown in the theaters. The blu-ray format supports 24p natively. However, it is impossible to show exactly 24 frames per second on a 60Hz television. 60 is not a multiple of 24, so there is no perfect way to fit them.
To display a 24p movie on a 60Hz television, the TV uses a trick called a 3:2 pulldown (also called Telecine). Each frame is split in two interlaced frames of alternating lines (depending on the media, it could be already stored this way). To display the video, it first shows the first 2 interlaced frames, followed by the next 2 plus repeating the last one (making it 3). This creates a 2-3-2-3 pattern, where one frame out of 2 is displayed longer on the TV. The picture to the right shows that effect. A television supporting 24p playback does not have this issue. For a LCD/LED display, this means a refresh rate of either 120Hz or 240Hz. 24 frames fits exactly in 120 frames per second. 120/24=5, so each frame is displayed 5 times. There is no need for the 3:2 pulldown technique, each frame has exactly the same time on the screen.
Is 24p playback worth it?
24p playback is only worth it if you are watching a lot of movies, not normal TV shows (who are filmed at 30 frames per second so they do not have that problem). The difference is small and you can normally only see the 3:2 pulldown artifacts if you are really looking for it. Consider it a nice bonus for 120Hz televisions, but not a primary buying factor.
The refresh rate is getting abused by manufacturers, especially with their own inflated numbers. A high refresh rate does not guarantee to be motion blur free, but we do recommend the upgrade to a 120Hz refresh rate (not more though). A real 24p playback is also a nice feature to have on a 120Hz television when watching movies.