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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."
They're ghostbusting.
Remove one of the advantages of LCD screens, why don't you?
In other words, to fix a barely-annoying problem with LCD displays they're willing to get rid of one of the greatest benefits. I'd rather deal with ghosting than have to go back to the days of CRT eyestrain.
Isn't ghosting problem related to the speed at which crystals can reorient?
hilarious
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.).
I recently bought a 17" LCD monitor. It has excellent colour reproduction and I can't notice any ghosting even when playing FPS games. Is there any reason this same technology can't be used on LCD TVs without the need to make everything flicker? I can only guess that the cost is prohibative once you go beyond a certain screen size, but surely the larger pixel size of TV (as opposed to a high resolution monitor) would make fabrication easier.
Early LCD displays were bad, sure, but these days I use a CRT at work and a low-end 17" Advueu LCD display at home (on which I watch both TV and DVDs as well, in addition to gaming), and I can honestly say that the LCD's display quality--contrast, brightness, sharpness, lack of distortion--is far better than my Optiquest at work, and I haven't experienced anything even suggestive of a ghosting problem, whether while watching action films or playing FPS games.
STOP . AMERICA . NOW
FINALLY. Boy will I be glad when CRT technology becomes cheap enough to replace those dinky, thin, horridly outdated panel displays. Then we can fully realize the classic sci-fi television wet dream of dozens of small egg-shaped monitors placed mere fractions of feet apart to simulate a single, moderate-sized screen!
Well but when will wew see TVs using OLED technology. For sure they will be alot better than LCD counterparts.
Ghosting also comes from reflections of incoming radio waves though I'm not sure people watch 'wireless' TV any more.
Doesn't it make you feel good to know that our freedoms are protected by politicans, lawyers and journalists.
While the pixels adjust their color, the backlight is off, and it will only switch on when the image is ready -- three times brighter than in a normal LCD TV to compensate for the dark period -- before going dark again.
Won't this make the flicker, oh, I don't know, about three times worse? I realize it's three times an LCD, not CRT, but still that seems like it could cause Pokemon-style seizures or something. Like you said, thanks, but no thanks.
I must admit that I've never even noticed this problem with LCD screens. Maybe I'm just incredibly unobservant, but you'd think that something that's known as "the main drawback of LCD TVs" would be noticable to even the casual watcher.
:)
When I saw the title of this article, though, the first thing that came to mind was this old TV that belonged to a club at my highschool. It was hooked up to a little camera on a remote-control robotic camera mount that a former club member had created, so the idea was that people sitting in another room could swivel it about with a joystick. Unfortunately, the mount broke, so the camera (which then became known as buttcam, due to its lowered position) ended up stuck looking in the same direction for some long period of time. This background image eventually got burned in somehow, and it got to the point where people could walk in front of the camera and appear transluscent on the TV.... and the end result was something that deserved the name "ghosting" far more than anything an LCD TV can do
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.
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I'd rather deal with ghosting than have to go back to the days of CRT eyestrain.
There are many reasons why CRTs cause eyestrain, and I'm not convinced flickering is one of them, especially today when most screens can refresh at 85Hz at 1600x1200, and even higher at lower resolutions.
Another problem is the cathode ray tube which by design creates a static electric field on the screen. This field will first attract dust particles in the air, which are then charged with the same polarity as the screen and as a result, they are shot from it, directly at the viewer, something which causes dry eyes. LCDs do not suffer from this problem.
Another problem of the CRT are the analog pixels, which are not perfectly sharp. They are smeared, because the graphics card cannot make abrupt enough changes between colours, and the neighbouring pixels are further smeared as they travel along the VGA cable. (Becomes really noticable at high resolutions and high refresh rates. The signal is pushing the bandwidth limit of the cable). They are also smeared because the electron beam used to paint the pixels is slightly fuzzy. As CRT-screens age, they may increasingly loose focus. Depending on your type of CRT age/price), the image may be blurred further by coatings put on to reduce reflections.
Our vision really dislikes not being able to focus on things perfectly. It puts a strain on the small muscles used to contract the lense inside our eyes.
LCD-pixels are perfect rectangles and does not suffer from these problems as long as a digital interface is used.
Today CRT-screens are superior when it comes to color reproduction, dynamic range. They are also superior when displaying moving images, because of their strobing nature. These new strobing LCDs may change this, something I'm excited about.
A witty
Secondly, the image loses color definition due to the backlight's frequency not necessarily producing the same amount of light pure color. Some times red may be better, some times green. If it gets really bad the a color can be completely skiped. Depends on the addressing method of course.
Thirdly if the addressing method prevents the color definition from being an issue as multiple colors are being addressed at once lines may appear over time, or the screen may noticeably flash.
Lastly there is some attempt to increase the power of white while flashing. This can effect the chromaticity of the white (read colors making it up) and make it biased toward yellow (usually). The brightness can also bleed through the black and make the over all contrast ratio suffer.
Now if they got it to work properly, good for them. I'd just rather not get the first model with this tech if I were you.
I'd say more, but my guild is raiding.
The last time I saw this technology was at the 2004 SID (Society for Information Display) show, in Seattle. LG/Phillips had one in their booth. I believe they were using LEDs for the backlights and were cycling rows of them in time with the LCD update. Being 60 Hz, the flickering was noticable, but the ghosting was completely absent.
Here's the problem: With a TV or movie screen, the image is flashed very briefly (on a TV, different parts of the screen are flashed at different times, but that's not important), and your brain stitches the scene together. The hold time on the image is VERY brief, so while it looks like a steady picture, it's really a succession of flashes with relatively long periods of darkness in between then.
With an LCD, on the other hand, you could say that the hold time is as long as the frame period (16 milliseconds or whatever). The LCD has no periods of darkness. With the CRT and movie screen, your brain is what stitches the images together, inferring the motion. With the LCD, you actually see the image change, and your brain perceives that as a smear. IIRC, what's happening is that persistence of vision is working against you and you end up seeing two frames at once.
Besides, raster-scanning the backlight, there are two other things that can reduce the smearing effect. One is to increase the frame rate. The higher the frame rate, the smaller the motion steps. It essentially reduces the hold time on each frame.
At the show, I went to a seminar by a guy named Kompenhouwer. For any device, you can mathematically model how it converts its input to output. This is referred to as a "transfer function". This guy developed transfer functions for the LCD and for a CRT and inserted a filter (It was really precomputed in software, but you could do it in real-time) between the video signal and the LCD that applied the CRT transfer function and inverse LCD transfer function. Those together cancel out the smearing effects of the LCD and make it look more like a CRT. For static images, the filter does nothing, but as I recall, the effect of the filter on motion is to amplify the high-frequency components of the image in the direction of motion. I think that as long as you are tracking the motion of the moving image with your eye, it looks right, but if you don't, it looks weird (but I may be remembering that last bit incorrectly).
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.
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That's a case of solving a problem that affects less than 1% of the population (Your specific application where ghosting/motion blur is actually a problem, as opposed to 99% of the population for whom it's been solved adequately on any decent LCD made in the past 5+ years.) in return for bringing back a problem that affects 25-50%+ of the population (flicker-induced eyestrain and headaches are extremely common) and produces SEVERE health risks for a non-insignificant number of people.
retrorocket.o not found, launch anyway?
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.