The refresh rate of a screen is the number of times per second that the picture is "drawn" on it. In theory, a higher refresh rate should equal a better quality picture because it cuts down on blurriness. A 120Hz display decreases the appearance of "film judder" or blurring that might be noticeable to some on a 60Hz screen. Improvements beyond a 120Hz refresh rate are unnoticeable.
|Picture Quality||Smoother than 60Hz. Works well with TV and film. Quality may decrease if wrong settings are used (e.g., deinterlacing effects on non-interlaced, digital TV).||Less smooth than 120Hz, prone to "film judder" and blurriness. TV footage more likely to appear smooth than film due to frame rate differences.|
|Price||Varies by TV size. Slightly more expensive than 60Hz, but likely worth it.||Varies by TV size. Slightly less expensive than 120Hz.|
Frame Rate and Refresh Rate
What Is Frame Rate?
Frame rate is how often a video source can deliver a frame of visual data to a screen for display. The frame rate is a property of the video source, not the display screen. Videos are often recorded at 24fps (frames per second) or 30 fps. In the U.S., the standard frame rate for broadcasts (NTSC) is set to 30fps, but if you were to view a video at this speed, it would seem jerky and slow. This is where refresh rate becomes important.
What Is Refresh Rate?
To make sluggish, if standard, frame rates seem smoother, screens "refresh" a frame more frequently by creating a duplicate of some images or creating a pseudo-transition with motion blur effects. This gives the appearance of a higher frame rate when there actually isn't one. For example, if you have a 30fps video source, a 60Hz TV will display each frame two times a second. Thirty frames per second work nicely with 60Hz because 60 is divisible by 30.
Frame Rate Difficulties
Film can complicate matters, as it is typically shot at 24fps. This means that a TV with a 60Hz refresh rate cannot evenly distribute frames, and that film which goes to video broadcast at 30 frames per second will not look the same as it did in the cinema. TVs can use an interlacing process known as 3:2 pulldown to improve smoothness; however, this is an imperfect process, and more perceptive viewers may notice film judder, flickering, or "tearing" effects.
In contrast, a TV with a refresh rate of 120Hz does not have to do anything special to display video or film, as 120 is divisible by both 24 and 30. This means that, in general, 120Hz will result in a smoother viewing experience.
The following video further discusses the main differences between 60Hz and 120Hz TVs.
Higher Frame Rates
Sporting events are often filmed at a higher frame rate per second than film or regular video, and some films, like Hobbit, are now filmed at higher frame rates, too. Filming at a higher frame rate removes some of the need for motion blurring, which means that smoothness of the video should look better on all modern TVs. However, some viewers will find the realness ironically fake looking after years of viewing video at lower frame rates per second.
To see how how a higher frame rate changes a viewing experience watch the video below.
Interlacing and Deinterlacing
Modern high-definition TVs, like LCDs and plasmas, use something called progressive scanning, which makes for inherently smoother imagery than older TVs were capable of producing. However, not all video footage is made for progressive scanning; many videos or films are broadcasted in interlaced form. To accommodate this, modern TVs employ a technique known as deinterlacing, which converts old interlaced footage to a non-interlaced (progressive) form. (See also 1080i and 1080p.)
Visual defects, such as combing, can occur when deinterlacing is used on footage that is not interlaced in the first place. If you're picky, you may often need to change your TV's settings to accommodate the range of footage it may come into contact with.
All modern TVs offer refresh rates of 120Hz or higher, but 60Hz TVs are still around and may be two to three hundred dollars cheaper, depending on TV size.
Some manufacturers now say they offer refresh rates of 240Hz or higher—usually for a much higher price—but in late 2013, CNET reported that this is often just clever marketing, and that a number of 240Hz TVs actually have a refresh rate of 120Hz (or lower), only with added smoothing effects. In any case, refresh rates higher than 120Hz probably do not add any obvious value outside of some decrease in motion blurring.
- 48 FPS and Beyond: How High Frame Rate Film Affects Perception - Tested
- Compare frames per second: which looks better? - Frames Per Second App
- Fake refresh rates: Is your TV really 120Hz? - CNET
- Unnecessary deinterlacing, when is deinterlacing not needed, with examples - 100fps
- What does refresh rate on my HDTV mean? - HowStuffWorks
- Why 24p? Is it intrinsically better than other frame rates? - Ask MetaFilter
- Wikipedia: Hertz
- Wikipedia: Refresh rate