LCD Response Time - Technical Question Explained

[jg1234]

Hi Folks,

I have always found this site helpful for the real technical questions. Maybe someone could help me understand these tech specs a little better?

Listed : Response Time - Ta=25(degree sign)C Tr+Tf=8ms

1. - What does Ta listed as a degree have to do with response time?
2. - Does Typical rise + Typical fall mean black to white to black?
3. - Is black to white response more accurate/faster then gray to gray ?
4. - Is there a standard that all manufacturers can follow.

Thanks in advance - jg1234

 

[schwinn]

Ta = Ambient temperature, in degrees Celcius, in this case. Remember than LCDs are Liquid Crystal displays... liquid will behave differently at different temperatures, hence Ta can significantly affect response. After all, the crystals in the liquid need to physically move to block or allow light to pass... this movement is a function of the viscosity of the liquid, which can be affected by temperature.

Yes, Typical Rise + Typical Fall means black to "set point" to black. The time to rise and fall is the response time.

White to black (0-255) is typically faster, as the LCD pixel can be overdriven to get there "faster". Manufacturers often quote this lowest number to make their panel look better than others, but the reality is that gray-to-gray is slower, since it can't be overdriven, and this is where you normally work anyway.

The timing is pretty standard, though, as mentioned above, it's still kinda lying. The ideal measure would be a graph, showing the latency across a wide band of levels, but they don't want to confuse Joe Sixpack, nor do they really want you to see this information, as it shows the truth behind the monitor's speed.

I suggest you read up the test procedure here: http://www.tomshardware.com/2004/09/23/_thg_unveils_new_lcd__benchmarking_method/page9.html and see what is tested, and how its tested, to get an idea of what's what. Note that I provided a link to the middle of the article, because it shows a typical latency curve for a "16ms" screen - note how it's latency is 27ms for some gray values...

 

[jg1234]

Thanks schwinn,

Those answers are helpful and I think that link sums it up pretty good. There is obviously a wide variety between what actual response times will look like - I will keep that article handy.

I think between user reviews and the ones from Tom's site I should be better informed.

-Cheers - jg1234