What is refresh rate?

Question

what is the refresh rate on an LCD newer tv's are getting 120Hz refresh rate, but what does that exactly mean? What does it have to do with frame rate?

Answer 1

Refresh rate on a TV represents the number of times that a complete top-to-bottom scan is made on the screen. On U.S. TVs, this is 60 times per second (60 Hz). In Europe it is 50 Hz.. The rational for this has to do with human vision. If image display frames are flashed too slowly, the eye will sense a flickering  effect. The frequency at which this occurs depends on the average scene brightness, but is around 50 to 60 Hz..

Our current analog TV uses an interlaced scan system. One complete FRAMEof video is displayed 30 times per second, composed of two FIELDS. The odd lines (1,3,5,etc) are displayed in 1/60 second, then the even lines (2,4, etc) are displayed in the next 1/60 second. The eye has enough persistence of vision to blend the two fields and perceive them as a single integrated frame. Because most frames have very little difference in content between the odd lines and even lines, this achieves the required 60 Hz rate to eliminate flicker.

HDTV systems use either 1080 line interlaced (1080i) or 720 line non-interlaced (also called progressive or 720p).

As far as 120 Hz is concerned, its tough to see how this accomplishes enough to be worth the extra cost. It's claimed that this allows 24 Hz movie content to be displayed better (120/24 is a whole number). It may also be possible to produce interpolated frames from 1080i content by smoothing out fast motion, such as in some sporting events. It would take a carefully controlled side-by-side comparison to tell if it's worth it.

Answer 2

It's the rate at which an image on the TV screen is updated.  Think of it like a frame of film, each frame "refreshes" the image.  The images refresh at a rate faster than the eye can see so the result is the appearance of motion.

Film refreshes as 24 frames per second.  Traditional TVs refresh at a little less than 60Hz (60 times a second).  120Hz refresh is the newest thing.

Supposedly 120Hz creates smoother motion.  Theoretically, this makes sense, but honestly, I can't see it.  C-net (http://www.cnet.com/) also did a review and said the people in their tests can't see it either.  Many of the newer sets with 120Hz refresh rates also have "smoothing" for films and that seems to make a difference, though.

I hope this helps

Answer 3

A screen with a refresh rate of 120Hz updates the image on its screen 120 times every second.  Frame rate tells how many images per second a video displays or a camera records.  That's why in some movies where there is a TV in the movie, you can see lines moving down the recorded screen because the refresh rate on the recorded screen does not match the frame rate of the camera recording it.  In other words, it records a snapshot of the screen different parts of the way through its refresh.