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Philips Working on LCD TV Ghosting
agentfive writes "Philips is working on a new lamp technology to eliminate ghosting. Ghosting is a problem in LCD TVs when tiny pixels creating the image take time to switch on and off and can't do it fast enough. The problem, widely recognized as the main drawback of LCD TVs, is apparent in fast moving objects such as tennis balls, but even slower moving images get fuzzy. Philips will do something similiar to a Cathode Ray Tube (CRT) by switching the fluorescent backlight on and off at a rapid pace."
Here's some real number for you. If the pixels can respond to any signal within 5 ms, that means the highest framerate that can be displayed without ghosting is 200 fps (1 / 5ms = 200 Hz). Which is more than you should ever need, and a big improvement on current LCD displays (a good consumer display has a ~20ms response time; 1 / 20ms = 50 Hz, not even 60 fps, but good enough for TV's 30 fps.).
Yep. So they're turning off the backlight during the time the crystals are re-orienting. Replacing ghosting with flicker. Might be less noticable because of the limitations of the human eye response.
Come on people, get the terminology right. Ghosting and motion blur are not the same thing!
Ghosting is when you get a faint duplicate of the entire on-screen image, slightly offset from what it should be. I don't think this can even occur on LCDs, I think it is a CRT-only problem, but if you use crappy analogue VGA cables, then who knows?
Motion blur is what you thing ghosting is. It is caused by poor refresh times, more specifically it is caused the amount of time it takes for a pixel to become unlit, or "switch off". So LCD screens that have a poor response time often show a trail after a moving object that looks like a ghost of the object.
Understandable that you could get the two confused, but still wrong.
I was just about to say the same thing.
I'd rather have slight ghosting (which on any modern LCD is not noticeable, at least for me) rather than 60-75 Hz flicker.
And unlike one of my best friends, I'm not photosensitive (i.e. gets sick in the presence of flickering lights such as fluorescents and low refresh rate CRTs). I have a friend that is photosensitive and does video editing work, and basically HAS to have one of the following:
Extremely high refresh rate (100 Hz+) CRT
or LCD
Even the extremely high refresh rate CRTs bother him a lot. I've had to reassure him when he goes monitor shopping that the fluorescents used in LCDs (almost always CCFLs) switch at rates a few magnitudes of order higher than normal fluorescent lights. (50-150 kHz instead of 60 Hz).
retrorocket.o not found, launch anyway?
RTFA Philips, Europe's biggest consumer electronics maker and among the three biggest TV makers worldwide, will not keep the technology to itself but has instead chosen to sell the new technology to any of its competitors.
Does God treat us as servants or friends? Check my homepage.
that is the annoying sound you're hearing.
Unitl you get a 3 chip DLP projector, there are moving parts (fan aside)
I think LCD has better color (personally) but the longevitiy isn't there.
As you know, the response times usually handed out are the time it takes for a pixel to go from black (0) to white (255) or white to black. LCD pixels can do this much faster then they can go from black to grey (128.) Another interesting attribute of LCD pixels is that they can go from white to grey faster then black to grey.
Some new LCD panels take advantage of this knowledge. To turn grey, it will push the pixel to full on, from black (0) to white (255), and then back down to grey (128)- and the whole process takes less time then going from black to grey. Unfortunately, in some circumstances you can see it and it might produce a "sparkle" effect on the video. But it's not distracting.
Anyways, to my original point, manufacturers are recording the response time from black to white, which isn't generally representative of the real performance of the LCD, which may be dismal when going from white/black to grey, or even grey to grey.
However, there's been advances in the manufacturing process and many new LCD screens reduce the ghosting to "can't even notice it" levels even without using tricks.
Friend of mine has a Samsung 19" LCD screen that claims 12ms response. I have a 24" HP 2335 widescreen that claims 12ms. My screen is a gem - it's an underrated screen for the price (You can get them new for $800) and it's in the "can't even notice it" category. Meanwhile, the Samsung is difficult to use for fast paced FPS type games.
I guess my point is that even though the manufacturer might claim 8ms or 10ms or 12 - they might not be bullshitting =) It could be a really awesome screen. But the only way to tell is by actually using the screen, because the current system of measurement doesn't take into account the TTG - time to grey.
- It's not the Macs I hate. It's Digg users. -
My friend who is an optometrist has told me the major reason why CRT monitors give you eyestrain and eventually damage your eyes is because of the thickness of the glass.
The image is projected onto the inside of the glass tube, which is nearly 1cm thick.
Your eyes are continually shifting focus between the front of the glass, and the back (where the image is).
Keeping your monitor clean helps a lot, as it stops the eye focusing on the front of the glass so much (less grime to focus on).
LCDs have glass that is very thin, so you don't get eyestrain
The movie camera along with the movie projector work on the principle of freeze-framing a segment of film, strobing that segment with a shutter, and then advancing the film to the next frame segment. That has the effect of flashing a still image, blanking the image, and then flashing a still image of the next frame. This famously flickers -- movies are not called "flicks" in slang for no reason -- but it is a particularly good way of representing scenes with motion in them that must work on some aspect of the physiology and neural pathways of vision.
The video camera and the CRT video monitor work on an entirely different principle. There is no shutter and no freezing of the image -- the image is continuosly scanned in a progression of horizontal lines. The CRT video monitor is also a good rendering of motion -- the combination of a video camera and CRT monitor, however is not. A lot of the "higher production values" TV shows are shot on film, scanned on to video tape, and then broadcast to get the motion sampling effect of the movie camera for better motion rendering among other effects.
The LCD may be far better tech for being parked in front of a computer monitor viewing source listings for 8-10 hours a day. When the LCD gets into people's living rooms when the HDTV deadline is approached (was it pushed back?), there is going to be a different group of people viewing entirely different content, and I am telling you there are going to be dissatisfied consumers viewing motion-blurred HDTV mush who will want their old TVs back.
My scrolling voice print application isn't even 1% of the population, but it has given me a perspective on viewing motion on LCD monitors. Very few movies or TV shows have steady pans -- the motion is usually confined to small portions of a scene. But there is something "not quite right" about TV viewed on LCD screens, and if you study the scene carefully, you will notice the motion blur.
As to flicker, I consider myself flicker sensitive -- I can see 75 Hz refresh as blinking away -- but 100 Hz or higher refresh is clearly available technology and looks rock solid as far as I am concerned. As far as motion blur, everytime I scroll text in an editor window, it is a mush of unsynched motion blur, but it does not have to be. We have enough computing power to smooth scroll editor windows if we want to -- DEC used to have a glass terminal that smoothed scrolled -- this would require vertical-retrace synched mouse events to pull off. Why don't we have that -- is the geek community so very happy with blurred text scrolls?
Anyway, some dudes at Philips are experimenting with an LCD version of the movie projector as a good way to represent blur-free motion. If they market it, you will be able to go down to Sears and view the Philips LCD side by side with the conventional LCD and as a consumer decide for yourself whether the crisper motion is balanced against flicker and whether you like the conventional LCD better. No one is pulling your conventional LCD computer monitor from the market.
Fluorescent lights with magnetic ballasts flicker at 120Hz. It turns off 2 times per cycle when the voltage crosses 0.
Most newer fixtures use electronic ballasts though, which operate at a much higher frequency (5kHz+)