Manufacturer TFT Trickery.

[Kumagoro]

Reading posts it is pretty clear that many people assume that TFT response times are an absolute. What i mean is that people have been lead to believe that the response times are constant but from what i have seen they only ever list the fastest response time i.e black - white. shades of grey etc for example can take a lot longer than this sometimes more then three times as long. Ive heard of some being as low as 10 to 15 fps.

I know of 3 types of TFT process, S-IPS, MVA, TN+Film there might be one other starting with P but i cant remember.

TN+film which i think has the best response times but it has a poor viewing angle so mostly used on 15 inchers only.
MVA is slowest, by how much i dont know but it has really good viewing angle.

I know some of you probably already know this but it needs to be said again for others that dont.

Im currently looking for a new TFT and im having trouble finding specs which quote anything but the fastest time.

Anyone have links which give better specs?

[malfunction]

News to me. I was under the impression that response times had to be the amount of time from black to white and then back again. Also - I don't understand how it can take longer to change to a closer colour (i.e. to grey) than from fully on to fully off...

(EDIT: I'm not saying you're telling porkies - just suprised by the idea)

[SilentDeath]

Responce times quoted are usually the combination of rise and fall, iirc. So where you see 25ms, that means 15ms rise, 10ms fall, or something like that.

[Kumagoro]

It takes longer as the liquid crystal, to create a shade of grey (brightness may also play a part) as it has to rotate to a certain angle. for black and white it just has to be horizontal or vertical. So for grey the rise time,, im guessing the time it take to get into position, is longer.

http://graphics.tomshardware.com/dis...0/tft2-01.html

I havent read that guide yet but it seems to have some nice info in it.

[malfunction]

It takes longer as the liquid crystal, to create a shade of grey (brightness may also play a part) as it has to rotate to a certain angle. for black and white it just has to be horizontal or vertical. So for grey the rise time,, im guessing the time it take to get into position, is longer.

http://graphics.tomshardware.com/dis...0/tft2-01.html

I havent read that guide yet but it seems to have some nice info in it.

Have read the guide but am still a little confused by the idea. Surely if we have two ends of the spectrum (black and white I mean, or rather more correctly fully on and fully off cuz there's 3 sub pixels - RGB - each that need switching), one being horizontal (e.g. 0 degrees) and the other being vertical (i.e. 90 degrees) then it would take less time to change from 0 to 45 (or 90 to 45) than 0 to 90 (or 90 to 0)? That's why I thought you only usually noticed ghosting / blurring on fast moving objects that have a high contrast from the background image? (because it takes longer to switch from the two extremes which leaves a trail?)

[Kumagoro]

Im no expert on TFTs (only did a little at uni on it back in the day) so I cant really give a definate answer.

Im guessing that for some reason it is harder to control the crystals to make them align at an angle inbetween their max and min positions..

Reading something else it refers to Twisted Nematics (TN as in TN +film?) From what i can gather the liquid crystals are twised and applying a voltage makes them unravel. Varying the voltage makes them vary in the amount they unravel. So when they are twisted it lets light through and when unravelled it blocks it.

So it seems that to creates shades you need very precise control on the voltage.
The reason why it take longer to move just a little compared to the whole way I cant find out. Perhaps it has something to do with damping and angles inbetween need to be critically damped.

I imagine it this way, 0 V and 5V, on and off are like a wall (it cant unwind any further and it cant be twisted any futher. You cant go past that wall so you can get to it as fast as you like and slam into it. If you want to get a certain point near to it you have to be more careful and take your time otherwise you will overshoot. How true this is i have no idea as i cant find anything about it in that much detail.

[SHISH]

To get a more mechanical idea, try it with a spring loaded flip switch.
On to off to on is a simple flick...done.
On to somewhere in between needs a greater control of effort applied so takes longer.
Not strictly correct but you may get the idea.
Ther are several monitor test progs out there with free trial periods.
Just do a search and you may find some of the results a bit surprising when you use them.
Try http://techmind.org/lcd/ for info and http://www.monitortest.net/monitortest.asp.
Quite a few progs around just google for them.

[KDH]

I know of 3 types of TFT process, S-IPS, MVA, TN+Film there might be one other starting with P but i cant remember.

The other one is PVA(MVA is several manufactures name, PVA the others)

TN+film which i think has the best response times but it has a poor viewing angle so mostly used on 15 inchers only.
MVA is slowest, by how much i dont know but it has really good viewing angle.

TN is used for all low MS 19" monitors(L90D+, vx912b, samsungs new 8ms)

Im currently looking for a new TFT and im having trouble finding specs which quote anything but the fastest time.

Anyone have links which give better specs?

Some manufactures quote average, some fastest.

[davidstone28]

There's a thread about it here:-

http://forums.hexus.net/showthread.php?t=28409

[Kumagoro]

Thanks for the replies, Ill take a look at the test progs and the graphs in the other hexus post give you some idea of whats actually going on huh.

Its about time that the mags when they do reviews of TFTs use some progs like this to give a better idea which is actually good. They only ever seem to do grey scale checks and thats about it, never anything on the response. I want to see more of those graphs.

[davidstone28]

Have a look here as well:-
http://graphics.tomshardware.com/dis...17_lcd-05.html


Nowhere near 16ms is it?


Nowhere near 12ms is it?

Here's the "16ms" Sony:-


Xbit labs also have alot of response time graphs.

Classic example of people being taken advantage of by the marketing departments. I wonder how people are going to react when they're told that they're "16ms" monitor is actually closer to 25ms? Pretty shabby way of treating consumers, the majority of whom, simply don't know better.

[Kumagoro]

Nice find dave,

how are the graphs formed? is that the response time from white to that level? im guessing that 255 is black

[davidstone28]

Methodology is here

It's all written in EE lingo speak though.