I read a lot but how can a lcd advertise both? or whats the difference between 4ms and 4ms/120hz? Am I missing something. I work retail at BB and would like to fully educated my customers as best as I can. Thank you.

I read a lot but how can a lcd advertise both? or whats the difference between 4ms and 4ms/120hz? Am I missing something. I work retail at BB and would like to fully educated my customers as best as I can. Thank you.


I would google the topic for some information, but it is fairly complex. 120hz can either be something like black frame insertion or scanning backlights, which modulate between on and off states for each of the CCFL's (or insert a frame of black for every 2 frames of light), thereby "scanning" up and down the display. What it does is cut down the hold time of a frame, by something like 2ms. So if you have a 6ms response time, it makes it effectively look like a "4ms" display. In reality those are just marketing numbers, but there are some quantified tests floating around that show the impact. I believe 120hz should help more than reducing response time by 2ms, because of the way our eyes work. Our eyes take in information sequentially, so without something to introduce breaks in light between frames, our eyes average the information between subsequent frames and we get a "smear". Obviously as the response rate of the crystal (how long it takes it to filter light from one value to another, say 0-255 on the greyscale aka from black to white) increases, the time between subsequent frames decreases (though this is limited by refresh rate) and your eye holds the light value for less time.

Of course if you really wanted to get the full scoop, you would have to look at how long our eyes sample light info, what the "on" and "off" duty cycles are (how long the BLU is in an off state", and how that translates into hold times. On top of that, you have refresh rates to deal with.

But, I really commend you for trying to understand this stuff. Many retail employees are very bad at their jobs. I'm sure you'll be great if you're taking steps like these.

edit: Forgot to add something. 120hz displays like XB4 and LX177 use motion interpolation, which basically doubles the framerate to 120fps, and does something similar to black frame insertion, except it adds a frame that is the average between 2 subsequent frames and inserts it between them. It can create some pretty bad artifacts, though users of those displays haven't reported anything bad so far on these forums. Some high contrast tests with non-standard shapes like traingles can show pretty nasty artifacts. The reason that it improves motion handling is because now your eye is holding the average of the 1st 2 frames, meanwhile the 3rd (really the 2nd before interpolation) is shown distinctly. In theory.

I read a lot but how can a lcd advertise both? or whats the difference between 4ms and 4ms/120hz? Am I missing something. I work retail at BB and would like to fully educated my customers as best as I can. Thank you. 4ms is a response time - the time it takes to place a complete image (frame) on the screen. 120Hz is a refresh rate - the amount of time an image is displayed on the screen. At 60fps, a 60Hz display would display a frame for 16.7ms, a 120Hz display would display a frame for 8.33ms. Related, but two different measures.

It can create some pretty bad artifacts, though users of those displays haven't reported anything bad so far on these forums. I believe the fear of these sets producing "some pretty bad artifacts" is overstated. Second generation sets are due to be released this fall (JVC). Since the first generation sets were well received (reviewers) I believe the second gen will be even that much better.

"Where the 120hz Clear Motion Drive makes a difference is with moving images, like rolling text across the screen. This is where many LCD TVs fall short, so the fact that text is crisp with defined edges (as opposed to blurred edges) when moving is hugely critical. This is something I can't overstate. This is great when watching a moving person, like with sports or in an action movie." http://tv.about.com/od/lcdproductreviews/fr/JVC_LT37X987.htm

"For those of you, like me, who have an aversion to motion blur, this is a big step in the right direction." http://hometheatermag.com/lcds/1106jvclt37x987/

When they get down to 1.5ms with no interpolation like CRT, then they'll have something. Unfortunately no one wants to sell or buy CRT-RPTVs anymore. But then again, when has the general public really cared about great picture quality. I think the main criteria for a set today is its weight! :eek: