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LCD refresh rate

L

latief75

Limp Gawd
Joined
Mar 30, 2005
Messages
459
i noticed that some LCDs could be run at 60, 70, or 75 hz refresh rates, i know how this effects a crt, but what about an LCD ? is it a good idea to run on the higher refresh rates ? or should you go with the lower refresh rate?

who has any input on this ..?
 
I would also like to know about this. Besides changing the FPS using Vsync, is there any other advantage to uping the refresh on LCDs?
 
On my first lcd (NEC LCD1765) I thought the image got a little sharper when I turned the refresh rate down to 60. My others don't really seem to behave like that, but it's something to consider I guess.
 
If I recall, it's the LCD's response time is the equivalent to the CRT's refresh rate. I don't think the LCD's refresh rate matters.
 
Yeah, they are 2 different things, since CRT and LCD function differently, CRT scans down the tube (refresh rate) while all the pixels change on an LCD (response time).
 
Yep to my eyes there is ZERO difference between 60hz and 75hz on my LCD. I run 75hz cause thats what it says is the highest.
 
this1tear said:
If I recall, it's the LCD's response time is the equivalent to the CRT's refresh rate. I don't think the LCD's refresh rate matters.
Click to expand...

You are correct - it doesn't matter. "60 Hz" on an LCD is NOT "60 Hz" on a CRT. A CRT scans a little beam (well, three of them) down a reactive piece of glass and draws the screen from top to bottom (it's more complex than that, but that the basic functionality). When set at 60 Hz, the screen is updated 60 times a second, pretty fast actually. When at something higher, like 75 Hz, the screen is updated 75 times a second, which is much easier on your eyes.

LCDs don't update the screen that way - each pixel is turned on / off depending on the color shade as it changes, not the entire screen. The LCD on my laptop and my system at home are both "60 Hz" and there is zero flicker.

The "important" spec on LCDs is response time - how long it takes that pixed to turn on / off (rise / fall) - the longer it takes, thus the term "ghosting" where the image is still on the screen because the pixels can't keep up with the changes.

So, In summary, the "refresh rate" on an LCD doesn't mean squat. Well, it does mean something, but isnt' the same as on a CRT.

Peace,
Tim
 
Actually, I heard somewhere that the backlight from an LCD is the one that runs at 60 Hz... but don't quote me on that. ;)
 
1c3d0g said:
Actually, I heard somewhere that the backlight from an LCD is the one that runs at 60 Hz... but don't quote me on that. ;)
Click to expand...

Edit. correction:
It runs on AC current but nowhere near 60 hz...here's why:
A very thin layer of light emitting phosphor is placed between two thin electrodes. One is opaque and the other is translucent to allow light to escape. When AC current (400 - 1600 Hz) is applied, the phosphor will then rapidly charge and discharge, resulting in the emission of light. The brightness and color of the light depends on the chemical composition and dye pigments of the phosphor.

Here is how it works: The AC adapter plugs into a standard 120Volt/60Hz outlet, the AC current is transformed to 12V DC current and goes into the inverter driver, in which the DC current is "inverted" back into AC at 120V (400 - 1600Hz). The voltage and frequency of the inverter will depend on the size of the EL lamp.

Source:
EL Lighting FAQ
 
Will a 75Hz refresh rate give you faster framerates on an LCD than 60Hz?

For instance, say you run your LCD with vsync on and 60Hz. The framerate will lock at 60FPS.

If you increase the refresh rate to 75Hz the framerate will lock at 75FPS. Will the LCD attempt to display the extra 15 frames, or does it revert back to 60FPS?
 
The short answer is no. LCD will display only what videocard will ask it to display. The framerate is dependent on the software and how well ur system can handle it, not on the qualities or refresh rate of teh LCD, so vsync at 60 ot 75 hz does not guarantee that ur framerate will be 60 or 75. What it does is to eliminate tearing which appears when videcard tries to feed more frames per sec to the screen than the latter handle :D In fact, with vsync on u might see ur framerates go down, if ur software (game) does not support triple buffering :D
 
TehQuick said:
The short answer is no. LCD will display only what videocard will ask it to display. The framerate is dependent on the software and how well ur system can handle it, not on the qualities or refresh rate of teh LCD, so vsync at 60 ot 75 hz does not guarantee that ur framerate will be 60 or 75. What it does is to eliminate tearing which appears when videcard tries to feed more frames per sec to the screen than the latter handle :D In fact, with vsync on u might see ur framerates go down, if ur software (game) does not support triple buffering :D
Click to expand...


Thats true, if you system can handle it and it caps off higher then 75 at the reso and setting you running the game at, it will cap at whatever you set your refresh to. Now this doesnt have the same effect on LCD as it does CRT. The reason why we use Ver Sync on a CRT is causing of tearing in the screen, reason being is that if the FPS is higher then the Refresh, it will tear edges as the CRT trys to keep up. This isnt the case with LCD, doesnt matter what the refresh is, it will not tear. So refresh is pretty much USELESS on lcds.
 
Highlife said:
Thats true, if you system can handle it and it caps off higher then 75 at the reso and setting you running the game at, it will cap at whatever you set your refresh to. Now this doesnt have the same effect on LCD as it does CRT. The reason why we use Ver Sync on a CRT is causing of tearing in the screen, reason being is that if the FPS is higher then the Refresh, it will tear edges as the CRT trys to keep up. This isnt the case with LCD, doesnt matter what the refresh is, it will not tear. So refresh is pretty much USELESS on lcds.
Click to expand...

Actually, I see tearing on LCDs too, it's really bad in Doom3 :D Vsync tho is bad since I couldn't enable triple buffering :(
 
@ Highlife: You are WRONG on that. I've seen tearing myself on my 15" LCD (turn off V-Syn, load up Unreal Tournament on a fast PC and play with a lot of bots on a map). I guarantee you will see tearing. :(
 
1c3d0g said:
@ Highlife: You are WRONG on that. I've seen tearing myself on my 15" LCD (turn off V-Syn, load up Unreal Tournament on a fast PC and play with a lot of bots on a map). I guarantee you will see tearing. :(
Click to expand...


Wow, i dont see any tearing at all....maybe it has to do with the screens itself....im using a Sceptre Naga II which is a TN screen, 12ms.....even when running FPS waaaay higher then refresh rate (VS off always), there is ZERO tearing anywhere. Which screens are you using?
 
Yeah, part of the reason I ask this is because I'm trying to figure out how to get the highest FPS without tearing on my 2405FPW.

The tearing is quite noticeable at 60Hz, so it sounds like 75Hz will help that issue. It's too bad I can't run at 1920x1200 at anything higher than 60Hz :(

Anyone know what the highest widescreen resolution that supports 75Hz is on a DVI connection? Or, if I were to use powerstrip would I be able to force it up to 75Hz? Any risk involved in doing that?
 
PKFGimpy said:
Yeah, part of the reason I ask this is because I'm trying to figure out how to get the highest FPS without tearing on my 2405FPW.

The tearing is quite noticeable at 60Hz, so it sounds like 75Hz will help that issue. It's too bad I can't run at 1920x1200 at anything higher than 60Hz :(

Anyone know what the highest widescreen resolution that supports 75Hz is on a DVI connection? Or, if I were to use powerstrip would I be able to force it up to 75Hz? Any risk involved in doing that?
Click to expand...

If you have a Nvidia card, you can use NV Refreshtool....just search it on MSN or Google and it should pop right up. Works great...

im going to log UT2k4 and take a picture of it, you guys tell me if you notice any tearing.
 
My thought on the refresh rate of a LCD is that the LCD has a fixed clock, probably at 60 hz, so no matter how much info you send it ie 75 hz instead of 60hz it will still only show at 60hz due to the LCD display's clock.
 
Highlife said:
Wow, i dont see any tearing at all....maybe it has to do with the screens itself....im using a Sceptre Naga II which is a TN screen, 12ms.....even when running FPS waaaay higher then refresh rate (VS off always), there is ZERO tearing anywhere. Which screens are you using?
Click to expand...
@ Highlife: I'm using a Dell 1504FP 15"LCD rated 25ms :( ...maybe that's why. If I turn on V-Sync, the tearing will go away completely. In any case my replacement will arrive in a few days in the form of a Dell 2405FP 24" LCD... ;)

PKFGimpy, are you still getting tearing when V-Sync is on? Then perhaps your card does not have enough horsepower to power the display...
 
Sorry for the angle of the photo, the person is standing behind me on the right so i can still play there are a few bots behind me and you can see someone is shooting me from behind....I also put up fraps so you can see the FPS, its in the left upper corner in yellow.

PicUT2k4.JPG
 
Disco_Stu_04 said:
My thought on the refresh rate of a LCD is that the LCD has a fixed clock, probably at 60 hz, so no matter how much info you send it ie 75 hz instead of 60hz it will still only show at 60hz due to the LCD display's clock.
Click to expand...

No not exactly. While its true that LCD's dont refresh like CRT's do the refresh rate does determine the rate at which updates are sent from the video card to the LCD. The DVI port on current video cards has a limiting bandwidth issue and this is why you can select higher refresh rates at lower resolutions but at higher resolutions like 1680x1050 you can't choose anything higher then 60Hz.

I've noticed on the 19" Hyundai L90D+ (native res 1280x1024) that if i would set the refresh rate from 60Hz to 75Hz the mouse pointer seemed to move much more quickly across the screen. This will also help when you to achieve higher fps when you enable v-sync in games.
 
Highlife, I'm not sure what you want us to see in your screenshot. Tearing is only evident when you objects move across the screen.... and your screenshot doesn't really show any movement.

I'm still wondering if increasing the refresh rate in powerstrip will be risky in any way. Like, is it possible to run a DVI connection at 65 hz or something? 70Hz?


EDIT: I've experimented a bit and it seems that my refresh rates aren't sticking when I play games. For instance, I set my windows resolution to 800x600 and it defaults to 75Hz. I can verify that its running at 75Hz by opening up the menu on the LCD display. It will say "Resolution: 800x600 75Hz". Then when I load a game up at 800x600, the LCD display will switch to 60Hz. How can I get the refresh rate to stick when I go into a game?
 
I am moving, this was when i was jumping from the shock rifle behind me, my friend took the pic behind me to my right.
 
Back when I was using Windows XP, the tool I used to lock the refresh rate was called RefreshForce. A word of warning though: this tool will absolutely set the refresh rate to whatever you set it to, so don't go crazy and put an insane number like 200 Hz or something like that... hell, some LCD's can't even take 75 Hz... so be VERY careful in what you do... I'm not responsible if you blow up your brand new 24" LCD... :eek:
 
Hrmmm.... so you're saying it IS possible to damage an LCD by messing with the refresh rate. If that's the case, maybe I won't touch them at all.

What exactly would get damaged if I did increase it? Doesn't it just increase the data throughput? What would get physically damaged if I messed with it?
 
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