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Television Media

Philips Working on LCD TV Ghosting 211

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."
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Philips Working on LCD TV Ghosting

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  • by Anonymous Coward on Wednesday July 27, 2005 @09:11PM (#13181990)
    They're ghostbusting.
  • Great. (Score:4, Insightful)

    by Anonymous Coward on Wednesday July 27, 2005 @09:11PM (#13181993)
    Remove one of the advantages of LCD screens, why don't you?
    • Re:Great. (Score:5, Informative)

      by Andy Dodd ( 701 ) <{atd7} {at} {}> on Wednesday July 27, 2005 @09:30PM (#13182105) Homepage
      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).
      • Re:Great. (Score:2, Informative)

        by mogwai7 ( 704419 )
        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+)
    • Personally, I have never noticed ghosting on ordinary video files -- even action movies, which I've watched on many a dell 19" screen.

      The only thing that I have noticed ghosting on is while gaming -- but, since I only use good LCD's (do your homework!) the ghosting is barely noticeable.

      What I'm left with, then, is a subtle, clean-looking form of motion blur in my games. Shit, some games steal my megahurts to create that effect! With an LCD, I get it for free!

      Trails? Set them to OFF, MOFO! For I -- I have an
    • Forget LCD, bring on the OLED [] ;)
  • by Osty ( 16825 ) on Wednesday July 27, 2005 @09:13PM (#13182005)

    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.

    • Looks like it's going to be even worse, FTFA:

      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.

      • Never had a flicker-related seizure, but I will say that CRTs below 85Hz are very annoying, and CRTs at 60Hz are downright painful.

        Unfortunately, every gaddamned monitor seems to default to 60Hz upon first use. As the majority of people can't even tell at 60Hz, I'm frequently "fixing" the refresh rates on friends' computers. They're always really confused and defensive about it too, as if I'm telling them there's something wrong with their monitor. A few people have flat out refused to let me change the ref
        • by melikamp ( 631205 )
          Hey funny you mentioned that. I cannot stand anything less than 75Hz, and strongly prefer 85Hz or higher. I can actually see the difference as I switch from 60 to 75 to 85, 60 being outright painful. And yet when I get to fix or use some friend's computer, I often see that they are running it at 60Hz. After several attempts of trying to explain what is wrong with that picture, I just adapted a rule of surreptitiously changing the refresh rate while the owner is looking away. After all, if they are able to n
    • by Rothron the Wise ( 171030 ) on Wednesday July 27, 2005 @09:38PM (#13182142)
      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.
      • by Johnno74 ( 252399 ) on Wednesday July 27, 2005 @11:24PM (#13182707)
        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 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).

          No they're not. If your monitor is even vaguely clean then it's pretty much impossible to focus on the glass (try it yourself. It's 99% transparent after all). You shouldn't be able to see it unless there's a massive refection on it (eg a window right behind you) - in which case, adjust the position of
        • Actually, the glass on a monitor is not 1cm thick; its only 5mm or less.

          I know this because I use a monitor faceplate as a serving dish (and no, it was never attached to a monitor, it came off an assembly line before being attached to the tube back and being coated with phosphor or aquadag, so its never been in contact with anything more toxic than anchovies).
    • Philips found the answer... now all they need is a problem!

      It's really sounding like something made to the marketing dept. One more little word to push when they're selling their products.
  • by William Robinson ( 875390 ) on Wednesday July 27, 2005 @09:14PM (#13182009)
    Isn't ghosting problem related to the speed at which crystals can reorient?
  • by xythis ( 882089 ) on Wednesday July 27, 2005 @09:15PM (#13182015)
    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.).
    • OK, but a CRT's phoshor still loses its glow quicker. Response doesn't mean complete change. Hitting the brakes cuz the light is red doesn't necessarily mean you stop before the intersection.
    • Actually, they're not. The response times that are quoted are rise/fall numbers, and those tend to be somewhat faster than grey-to-grey numbers. Try a FPS game on a 16ms display, and you'll see this -- despite the fact the display is limited to 60Hz refresh, and 16ms should be fast enough for 62fps, there's still ghosting in textures. There is an article on this here []. For example, Viewsonic's VX724 only needs 6ms to transition from white to black to white (two transitions), it takes 4ms to transition fr
    • Yes, but the problem is that, unfortunately, there aren't any 5ms LCDs yet. In fact, there aren't any 8ms ones, regardless of what the brochures tell you. Those figures are extremely optimistic (ie fake) figures for perfect conditions. In reality even an 8ms (or a new 4ms G-G screen) is often >20ms for many transitions. THG (yeah, yeah, spare me the THG bashing) did a good demonstration of this by showing the actual transition times for the monitors they reviewed. Quite simply, nobody comes close to
      • actually the viewsonic vx924 does in fact eliminate ghosting by responding in about 4-5ms. The tom's article pointed out that it still takes an avg of 16ms for the pixel to be within 10% of the requested color.

        I have 3 of these things and I can assure you they are nothing short of amazing. Set the refresh rate to 85hz and compare side by side with a CRT and there is absolutely no ghosting what-so-ever.

        Even the tom's article gives some credit here [] IMO they were way to calm about this monitor! people dont RT
    • "If the pixels can respond to any signal within 5 ms"

      I took the liberty of adding the emphasis to the keyword there, because that's the whole problem with the current generation of LCDs.

      Yes, the day a TFT can completely switch between any two colours in 5ms or less, will be the day we'll stop complaining about ghosting anyway. Heck, even 12ms will do just nicely, _if_ it can actually switch between any two colours in that time.

      But the problem with current monitors is that the numbers claimed by the manufact
  • by fake_name ( 245088 ) on Wednesday July 27, 2005 @09:16PM (#13182018)
    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.
    • Actually, iirc from a previous discusion about LCDs on AVSforum, the larger a crystal, the longer it takes to reorient. The little pixels in a 17" display (or, even better, the 15.4" WUXGA on my laptop) can be switched pretty fast, but you put up a 1024x768 array over 40 or 50 inches and you're talking big pixels.

  • by aussersterne ( 212916 ) on Wednesday July 27, 2005 @09:17PM (#13182025) Homepage
    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.
  • by systemic chaos ( 892935 ) on Wednesday July 27, 2005 @09:18PM (#13182029)
    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!
  • OLED (Score:4, Interesting)

    by camcorder ( 759720 ) on Wednesday July 27, 2005 @09:19PM (#13182044)
    Well but when will wew see TVs using OLED technology. For sure they will be alot better than LCD counterparts.
    • Maybe we will someday see them, if the color quality improves, and they can make large enough OLEDs for a viable price.

      To get new technology, regardless of manufacturing costs, you have to pay the 'new technology' price... so it's going to be a LONG time before we see them at Walmart, Circuit City, or BJs.
  • by Hannah E. Davis ( 870669 ) on Wednesday July 27, 2005 @09:35PM (#13182124) Journal
    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 :)
    • 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.

      It's not easily noticable with normal action. It just looks slightly blury around motion, which can match with the colors well-enough.

      Where it looks REALLY bad is in animation, since you have the sharp contrasts between neighboring pixels. And also, if you watch most news p

  • by jcr ( 53032 )
    So, they're going to re-introduce flicker to deal with ghosting?

    Doesn't sound like a win, IMHO.


    • As a person succeptible to flicker induced seizures, I find this move outright evil.

      As you say, they're going to reintroduce a major annoyance for many (and a very real health concern for me), to appear like they've solved the ghosting problem? It doesn't really even sound like they're solving the ghosting issues but just relying on the average person's afterimages to give that perception. I'm sure we'll see a huge return of strange, unquantified headaches that were a common ergonomics complaint back duri

      • by jcr ( 53032 )
        As a person succeptible to flicker induced seizures, I find this move outright evil.

        Would a 60 Hz flicker trigger your seizures? That's the same flicker rate that you'd get from broadcast TV.

    • Agreed. I am a big fan of LCDs, and on modern displays ghosting doesn't even seem to be an issue. It seems ridiculous to bring back flicker to eliminate something that doesn't even seem to be a problem anymore.
  • by feyhunde ( 700477 ) on Wednesday July 27, 2005 @09:47PM (#13182177)
    I've some experience in the AMCLD business and gotta say this ideas been around for a while and has several issues. Depending on the display it's more likely to increase aging effects of the back light, making your monitor die that much faster.

    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.

  • Offtopic: LCD vs DLP (Score:2, Interesting)

    by maxrate ( 886773 )
    Could we get a poll on slashdot of fav matrix technology?

    LCD / DLP / CRT / PLASMA / ??? / ???? / ?????

    I prefer LCD over everything else at the moment, including DLP. I don't like the effect of the pixel being switched on/off the produce a shade, where LCD can be varible (control wise) to produce variable shades.

    I have owned several projects since 1997. I've never owned a CRT projector, however I like the color on the LCD ones by far. I notice the LCD's don't last as long as DLP. I am using them for ente

  • As it is, the cold cathode fluorescent lamp in LCDs doesn't last all that long. 50k-100k hours before it loses 50% of its brightness. Turning it on and off a lot does not lengthen its life. As with all electronic or electromechanical devices, the most amount of thermal stress you can put on them under standard conditions is to turn them on and off.

    So what are we looking at with these new screens? Maybe half the already limited brightness half-life? CCFL tubes are not generally replaceable, even by technicia
    • Some of the early Apple Powerbooks (PB100 for example) had service replaceable backlights. They were about 5 mm in diameter (from memory) and extremely fragile. I don't even want to think about end users replacing these on a regular basis.

    • Re:CCFL tube (Score:3, Insightful)

      by lxs ( 131946 )
      As it is, the cold cathode fluorescent lamp in LCDs doesn't last all that long. 50k-100k hours before it loses 50% of its brightness.

      Our definitions of 'not long' seem to differ slightly. 50k-100k hours is about six to twelve years running contiuously, or about 15-30 years if you get off the couch once in a while and have your TV on for ten hours a day. I can't remember a CRT that was still crisp and bright after 20 years in service.
  • What about images that are composed of unusually large pixels?
  • by Theovon ( 109752 ) on Wednesday July 27, 2005 @10:23PM (#13182342)
    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).
  • switching the fluorescent backlight on and off at a rapid pace.

      I'm no expert but aren't fluorescent lights already off 99% of the time? It's just the way it has to be because of its design and the gas in them.
  • I hope these new displays fail horribly. This is the LAST thing we need...

    Modern LCDs have response times so low that the problem is nearly eliminated. Further developments such as overdrive (Increasing response times by going past the desired setting and then back again) have further improved it.

    So, WHY are they going to go and introduce flickering LCDs?

    This is like hitting someone on the head with a hammer in order to kill a fly. The "solution" is way worse than the problem.
  • Finally, an LCD monitor that can give me a headache like my old CRT

    I miss my headaches, yay technological advancement!
  • Adding a flash to the screen will make watching them tiresome. LCD's advantage in readability is the eye does not have to adjust to flickers that TV/Cathode Ray Tube use for persistence of vision. Over time the eye catches the blank spots, the variations in brightness and the pupil contracts and expands to match. LCD has a steady light. I recently started using an LCD screen at work, and I have no intention of going back to a CRT again. My eye strain issues are gone, I walk out of work not feeling tired. I
  • It's not called ghosting. It's called "motion blur". Scroll about halfway down and look at what some Anandtech writer just wrote about the whole subject: =40&threadid=1648775&enterthread=y []

  • I got me a big ass DLP projector and a helluva bright screen that covers half the wall.

    It sucks great steaming tourdes during the day, but at night- it's a fuckin' MOVIE THEATRE.

    Take your dinky LCD home with you, please.


    • It sucks great steaming tourdes during the day...

      That explains why I went the LCD route. Also, I love the kick ass wall mount [] that lets me move my 46 inch LCD [] about two feet from the wall and swivel it so I can watch it from my kitchen while making dinner.

      Not to say projectors don't kick ass, but hey, like OSes... different strokes for different folks... :-) And this isn't to say my TV has been flawless.. I have a Samsung LTP-468W (which took three tries for Samsung to get "right" with no dead pixels)

  • Ummm no bad bad (Score:2, Interesting)

    by Felinoid ( 16872 )
    I can see the ghosting and I can see the flicker.
    (CRT flicker and LCD ghosting) and I don't care.

    This could be a problem for Philips for a lot of reasons.
    People have a problem lumping an entire class of product together and "Once you've seen one duck you've seen all ducks".

    I've seen it in Linux and SUVs.
    Every Linux distro is diffrent and SUV is a class of vehical refering to many diffrent types of vehicals, Vans, MiniVans, Trucks, Jeeps etc.
    But people think all SUVs are alike, all Linux distros are alike.
    • Sitting in front of a Trinatron screen myself right now. I remember having numerous debates with customers in the early '90s trying to explain that the horizontal line(s) was not a flaw in the screen but was intended to be there. It was generally easier to point it out to them BEFORE they bought the screen that argue it with them later.

  • I always thought the problem was the crappy plasma tech. TFT should adress this problem but its probably not cheap enough thus the ugly hack they try to pull. I watch both movies and tv on my 17" LCD (TFT) and i cant say i have ever even noticed any ghosts in the picture. On cheap laptops with plasma screens on the other hand its all a crappy blur.

  • "Philips will do something similiar to a Cathode Ray Tube (CRT) by switching the fluorescent backlight on and off at a rapid pace." ...thus eliminating the only real advantage of LCD over CRT.
  • by evilviper ( 135110 ) on Thursday July 28, 2005 @05:45AM (#13183876) Journal
    Clearly, they are doing this simply to spit those of us who use XMAME. We just got rid of refresh-rate mismatches by switching to LCDs, and now the LCDs are going to be getting a 60Hz refresh-rate...

  • I moved from CRT as soon as LCD's came out because I'm migraine-sensitive to the refresh rates on CRTs. Even 100Hz.
    Please god I hope they don't put the flicker back in.

Machines that have broken down will work perfectly when the repairman arrives.