LCD TV

[Sigurd]

I am currently helping my wife in getting my in laws a new LCD TV. They aren't the richest people so the budget aren't that big.

The thing is: He (my father in law) read in some magazine that you at least need a 100 Hz TV. Anything below is crap.
As far as I understand the concept, the difference between the old TVs with CRT interlaced technology and the new progressive LCD technology, is that Hz doesn't matter as much in LCD technology as it does in the CRT technology.

However there are 100 Hz LCD TVs out there and I have to explain why progressive signals don't really depend that much on high refresh rates. When thinking about it - I realize that my current knowledge about this is not that great.
I know there is this thing called refresh rates which figures in milliseconds. But how this combines with the 100 Hz progressive screen line refresh rate is unclear.

We are currently looking at two TV screens : a 40 inch Samsung at Full HD (LE40B530) and a Sony 37 inch 100 Hz Full HD (KDL-37W5500). Both just under budget.

Any tech heads out there who could enlighten me about this 100 Hz vs 50Hz/60Hz issue on LCD screens? I have heard it is a Hype to want 100 Hz LCD TVs. You don't really need it.

[Beskar]

I love how you say "They aren't the richest people" then say about wanting 40inch 100 hz LCD screen.

Anyway, the human eye can only see 60hz/60fps. The average movie only runs at 24hz but to prevent flickering, they usually show each frame twice, sort of deal.

[Sigurd]

I love how you say "They aren't the richest people" then say about wanting 40inch 100 hz LCD screen.

Well.. they still have an old cathode ray tube TV which really works bad with the cable TV technology they have (included in their house rent).
You can get LCD and Plasma TVs from $2500 up to $5500, but their budget is max $1000. The TVs I mentioned are just under that.



Anyway, the human eye can only see 60hz/60fps. The average movie only runs at 24hz but to prevent flickering, they usually show each frame twice, sort of deal.Yes, and that is especially important when talking about CRT screens which updates the whole picture at a particular Hz rate. (100 Hz = 4x update)
But on LCD screens this is progressive - which according to my memory, updates each pixel line at a certain Hz rate - not the whole picture. Which translates to: each of the 1080 lines on a Full HD screen is updated individually at a given Hz rate. Hence why I personally don't see the necessity of buying into the hype of 100 Hz LCD screens.

There is something in the 5 ms response time vs. 100 Hz update rate though, that I would like to learn more about.

You have the Plasma screens with incredible fast respons time; 1 ms if I am correct, which have no flicker - (the pixels emits constant light??). Why would you need a 100 Hz Plasma?

[Xiahou]

Yes, and that is especially important when talking about CRT screens which updates the whole picture at a particular Hz rate. (100 Hz = 4x update)
But on LCD screens this is progressive - which according to my memory, updates each pixel line at a certain Hz rate - not the whole picture. Which translates to: each of the 1080 lines on a Full HD screen is updated individually at a given Hz rate. Hence why I personally don't see the necessity of buying into the hype of 100 Hz LCD screens.

There is something in the 5 ms response time vs. 100 Hz update rate though, that I would like to learn more about.
This may help clear things up for you- from Wikipedia (http://en.wikipedia.org/wiki/Refresh_rate):
Much of the discussion of refresh rate does not apply to the liquid crystal portion of an LCD monitor. This is because while a CRT monitor uses the same mechanism for both illumination and imaging, LCDs employ a separate backlight to illuminate the image being portrayed by the LCD's liquid crystal shutters. The shutters themselves do not have a "refresh rate" as such due to the fact that they always stay at whatever opacity they were last instructed to continuously, and do not become more or less transparent until instructed to produce a different opacity. Most of the TFT LCDs used in portable devices and computer monitors need a continuous refresh. The driving voltage determines the transmittance of the liquid crystal.

The closest thing liquid crystal shutters have to a refresh rate is their response time, while nearly all LCD backlights (most notably fluorescent cathodes, which commonly operate at ~200 Hz) have a separate figure known as flicker, which describes how many times a second the backlight pulses on and off. However they also have a refresh rate that governs how often a new image is received from the video card (often at 60 Hz).Also this:

Many high-end LCD televisions now have a 120 or 240 Hz (current and former NTSC countries) or 100 or 200 Hz (PAL/SECAM countries) refresh rate. The rate of 120 was chosen as the least common multiple of 24 frame/s (cinema) and 30 frame/s (NTSC TV), and allows for less distortion when movies are viewed due to the elimination of telecine (3:2 pulldown). For PAL at 25 frame/s, 100 or 200 Hz is used as a fractional compromise of the least common multiple of 600 (24 x 25). Until a 600 Hz refresh rate becomes available, PAL video will speed up cinema by a small percentage (currently 1 to 4 percent). These higher refresh rates are most effective from a 24p-source video output (e.g. Blu-ray Disc), and/or scenes of fast motion.

As far as LCD response times go, I've been told that once you're below 10ms the human eye can't detect the difference. Personally, I bought a 42 inch LCD HDTV last year for about $800 and I've been perfectly happy with it. Based on what I've seen since, they've only gotten cheaper.

[Husar]

The problem is with displaying movies and especially Blu-Rays with 24 frames per second, as they explain in Xiahou's quotes. I watch Blu-rays on my 60Hz Computer LCd and when the view pans slowly across a landscape for example, I often notice a rather visible stuttering because 60 is not a multiple of 24 so the screen has to show a few pictures twice and others three times, causing the problem. It's not THAT bad in my opinion but that may be subjective, I don't really notice any big problems in most movies and then I saved a lot of money as well. Matter of taste and preference I guess, 120Hz sounds like a good option to me if they value quality.