A recent question by one of our HDTV Magazine readers regarding LCD was: What does 4ms really mean? And how would that reconcile with the fact that a typical 60Hz frame rate would display each frame every 16ms? (8ms on a 120Hz display).

To accurately respond to these questions would take more than just a few sentences. The answers are not black and white, as I explain in the following article.

There seems to be a contradiction in the way these specs are expressed or interpreted for LCDs, and they are actually two different subjects that interact for the objective of display quality...

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Thanks Rodolpho for an extremely insightful and thorough article. I was the person that posted the question about the difference and it really helped me to understand some of the issues.

I originally thought of this question because I deal with stereo video. In the early years we wanted to have a stereo capable LCD panel and could never get one. When I saw LCDs advertised at 4ms and 8ms refresh rate I thought stereo capable LCD panels had finally arrived. Alas, it was not true.

However, with 120HZ LCD panels with 4ms refresh rate it now appears that one can easily buy a stereo capable LCD panel. But, maybe I am dreaming again?

There was one part of your article that was not completely clear to me. How is MPRT measured?

David

Great article. It also helps to illustrate a weakness (by my evaluation) of the entire marketplace. Specifically, that manufacturers are left to establish their own guidelines for their claims. It permeates this industry, just as it does the computer industry.

When everyone else (or the vast majority of the professionals) can clearly define what something means -- such as refresh rate or pixel recovery times -- why can't the manufacturers be held accountable to follow those accepted definitions instead of using subterfuge? Lately, I've been discussing with my brother why Samsung really does not produce a 500,000:1 Contrast Ratio. More than twenty years ago he was very angry over discovering that stated CRT diagonal dimensions on his monitor did not follow the guidelines mandated by Congress concerning TV screens (because they are not considered TV screens). To him, that was a complete lie. To me, the 500,000:1 Contrast Ratio claim is a complete lie -- but he accepts it willingly because it is convincing him that buying that backlit LED set is justified on that one "major difference" from every other set he's seen.

Similar buying decisions have been made concerning Response Time claims on LCDs, I'm sure. This was a great article to read -- if you're interested in the technical side of things.

Thanks for a great - simply said explanition. Does this also apply to DPL - rear projection HDTV's? I'd really be interested in a simular explanition about these sets.

DLP is a totally different animal. You have a chip with mirrors (one for each pixel) that reflect light from a lamp source. It either has a clear lamp with a color wheel (single chip) or separate red, green and blue lamps (LEDS in the newer ones) with separate chips (3 chip) to get the various colors. Each mirror is tilted to be either on or off.

The wierd part is that the 1080 chips use "wobulation" - the mirror array is actually 960x1080 so it displays half of the horizontal pixels, then moves slightly and displays the other half. It does this in 1/120th of a second so you get a full picture every 1/60th of a second.

David,

My article intended to clarify and simplify as much as possible the complex subject of LCD bluriness to help you with your questions, and I am glad it was useful to you.

If you want to know more about the MPRT measurement subject (as you requested), you might want to consult the following sources:

http://www.nanosoftware.co.jp/MotionArtifact/literature/SID04/43_04.pdf


http://www.photal.co.jp/english/product/mprt20_me_0.html

I will be doing a quiz at the end of the week.


Best Regards,


Rodolfo La Maestra

Rodolfo wrote:David,
I will be doing a quiz at the end of the week.


Best Regards,


Rodolfo La Maestra

Thanks! Hopefully, you won't be grading the quiz!!