LCD has zero flicker, no? so it has no refresh rate? for CRT, i have sensitive eyes, and can't stand anything below 75hz.
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With LCD, the picture does not go on and off line by line like CRT. Every pixel is always colored and the pixels just change colors (hence "ghosting" effect). But that doesn't mean that refresh rate means nothing for LCD. Refresh rate refers to how fast the data is transferred from the graphics card to the monitor. Response time is what's really important with LCD. My monitor has a 2ms response time.
Here, I stole this off another forum. Enjoy.
Link: http://www.tomshardware.com/forum/52152-3-refresh-rate
Refresh rate - video card
Refresh rate refers to how often the picture on the screen is updated. This is independant of whatever monitor you are using (CRT, LCD, DLP, Plasma, OLED, SED, etc...).
Assume you have a 60Hz refresh rate. That means that your video card is sending a new picture 60 times per second. It is sending the entire screen 60 times per second no matter what monitor you have or whether anything has changed on your screen. The monitor then updates the entire screen every refresh rate cycle (in this case 60 times per second). Again, it does not matter what monitor type it is; they all receive an entirely new picture 60 times per second (assuming it has a refresh rate of 60Hz).
Refresh rate - games/updating
Ignoring the specific issues of flickering on CRT monitors, refresh rate does have an effect on other things -- such as games and fast moving objects. As described earlier, refresh rate is simply how often a new (up-to-date) picture is sent to your monitor. If the refresh rate was too slow, then there would be a noticeable difference between what you did on your computer and what you see on your monitor. 60Hz (or 60 frames per second) is usually enough for most tasks. However, some very demanding users may be able to notice (and use) higher refresh rates like 75Hz for things like having that split second extra faster update in a game.
CRT flicker - the connection to refresh rate
It seems that many people perceive refresh rate as controlling the flicker on CRT monitors and assume that refresh rate has no affect on other monitor types like LCD; however this is not the case. Although there isa strong link between refresh rate and flicker, flicker on CRT monitors is a totally different issue from refresh rate. The concept of refresh rate has already been explained... so now on to the topic of CRT flicker.
Flicker on a CRT monitor is the result of how CRT monitors produce a picture. On a CRT, the electron gun fires electrons at the screen that causes the pixels to light up for a split second, after which, the screen immediately starts to fade back to black (no light). On a CRT, the picture goes in a cycle: the screen updates, the picture starts to fade back to black, the screen updates again (restoring the color), it fades back to black, and so on, and so on. A CRT simply cannot hold a constant picture; it must continually update to keep going. The slower this update, the more noticeable the period between updates (where the monitor starts to fade back to black). When the update is too slow, many people can notice the fading of the picture back to black between cycles (whether subjectively by getting a headache or objectively by knowing what they are looking at).
How does this relate to refresh rate? Since, as explained earlier, refresh rate is simply how fast a new picture is sent to the monitor, then that means if you have a lower refresh rate being sent to the CRT monitor, then the flicker (color, black, color transition) will be more noticeable; but if you raise the refresh rate, the CRT monitor will update more often and reduce how much you notice the flicker. So, as you can see, refresh rate is important to using a CRT monitor, but it is not something unique to CRT monitors.
Refresh rate and LCD monitors
On an LCD, things are completely different. The light comes from a constantly lit "white" bulb in the back of the monitor. In front of the bulb is a "screen" with millions of little LCD pixels on it. This is the part you see; it is the part that shows the picture.
Again, refresh rate comes into play. Whatever the refresh rate is, that is how often the LCD screen will change to show whatever the computer looks like now. Between refreshes, nothing happens. The LCD pixels stay the same... the backlight remains turned on... etc.... It is a constant picture that does not fade back to black like on a CRT. Thus, you should not see any flicker effect from this.
However, as described earlier, refresh rate is still how often a new picture is sent to your monitor, and it may have some impact in some rare cases.
Response time
While refresh rate has to do with the computer and how often a picture is sent to the monitor, response time is entirely a monitor issue. All monitors have a response time. Response time is the measure of how long it takes your monitor to change the picture (each time it is told to during each refresh cycle). Unfortunatly, LCD monitors have slow reponse times, causing them to change the picture slowly. For fast motion, this produces a blurring effect instead of sharp, distinct moving objects.
Now... assuming that you used a refresh rate of 60Hz, that means that you need to change the picture every 16.6 milliseconds. Thus, an LCD that is slower than 16.6ms is gonna have blurring in it. On the other hand, if you need the faster frame rate of something like 75Hz/FPS, then that would require updating the picture every 13.3 milliseconds. (Note: it is my guess that monitors actually need much more than these bare minimum numbers being mentioned.) So..., if the monitor's response time is not fast enough, then it doesn't really matter how high you set the refresh rate.
[code:1:4a78c69816]If you are interested, a refresh rate of 60Hz = 60 frames sent to the monitor per second. As you may have noticed, LCD monitors are often rated with a response time of so many milliseconds, or ms for short. One millisecond is 1/1,000th of a second. Doing a little math, we find that to achieve 60 frames per second refresh rate, would require updating the monitor around every 16.6msComment
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