LCD – For the Novice and the Expert
by Kristopher Kubicki on September 4, 2003 12:13 AM EST- Posted in
- Displays
Fixing a dead (sub)pixel?
The largest fear an LCD consumer has is that a dead pixel will ruin the display. While older LCDs used to be plagued by dead pixels, manufacturers are getting pretty good at producing monitors with (almost) no defects.When analyzing LCDs for dead pixels, there are a couple of pretty easy rules to follow.
1.) In almost every case, the monitor is shipped with a dead pixel. Very rarely does a pixel actually “burn out”. Thus, when buying an LCD, especially from a retail store, ask to see the LCD on before actually carrying it out the door. If a sales rep gives you a hard time, be persistent. It doesn’t cost Best Buy anything to ship a monitor back to Samsung, and they would rather make money off your purchase than see you walk out the door.
2.) “Stuck” pixels have no easy fix. Sometimes you can get the store to take the monitor back, but if you order online, it can be difficult.
As an act of desperation, some people recommend “rubbing” the pixel to see if it will come back to life. We have seen dozens of monitors and dead pixels, but unfortunately, this has not worked once. From the experience of others, the majority of dead pixels that are stuck red seem to be totally broken and no amount of rubbing will fix them.
Click to enlarge.
Above, you can see an image of an LCD screen. We attempted to rub out a red pixel (seen in the lower-center of the image). However, not only were we unsuccessful, we ended up scuffing the monitor, which is also visible.
Other pixels stuck off or on seem to have much greater chances of success. Personally, it seems that rubbing the pixels does more harm than good so continue at your own risk. Take a piece of lint free cloth and wrap it around your index finger. Push about 1/4 of an inch above the broken pixel with about as much force as would take to depress a doorbell. Pull your finger down past the pixel to about 1/4 of an inch below the broken pixel. Repeat in a left to right manner as well. If you’ve tried it about 10 times and are still without success, then you most likely are not going to be able to bring that pixel back to life (and you will probably have a light scuff mark on your anti-glare coating as well).
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KristopherKubicki - Friday, September 5, 2003 - link
#42 - this will be addressed in Part II =)Kristopher
Anonymous User - Friday, September 5, 2003 - link
Very nice article. Easy to read, fun and very informative.However, as someone here stated earlier, the reference to how some companies manage to get more than the 262000 colours with the 16ms AUO substrate is missing. It seems that they do this by alternating two colours, which would in effect mean the actual total rise and fall time for that one colour is more than 16 ms. But perhaps this is to be discussed in the follow-up to the article? I'm really interested in reading about the grey-grey times for the panels, so I'll be looking forward to part II.
AbRASiON - Friday, September 5, 2003 - link
Wouldn't touch one until it beats a CRT in every single way - periodFor work yes, sure right now, one res all day, no games, no worries.
For home, multiple resolutions, more dos boxes - linux sessions (ok I don't have any but if I did) - games which I don't have a strong enough video card for native resolution etc etc.
also the stupid ghosting / shading effect of the high refresh (16ms is too high)
Until it beats a CRT in every single way - I'm not going over - EVEN IF CRT's end up costing more.
Plus CRT's are getting better, my 22" Philips (100hz 1600x1200) is only like 45cm deep - quite short really considering.
virtualgames0 - Thursday, September 4, 2003 - link
I think you missed a big issue with LCD image problems that I have commonly observed. Most LCDs are very dim, and almost all of them I've seen are nowhere close to comparable to a CRT, the only ones I've seen that were comparable was the NEC.Another problem I have commonly observed is that the majority of LCDs have very visable "gate lines(as you called it in the artlce), so then you can see that every pixel is seperated, and it makes everything look pixelated, and it feels like you're trying to look through that mesh...
spikemike - Thursday, September 4, 2003 - link
I'm not 100% sure but i believe a 1280x1024 LCD monitor is actually built in a 5:4 ratio. So the pixels are still square.n0d3 - Thursday, September 4, 2003 - link
What I missed, and I'm sure it will be coverd in an update, was something more about resolutions. Here's why.Today, people seem to be using 'weird' or 'odd' resolutions a lot, basically because it seems better to have bigger numbers. For instance, 1280x960 is not acceptable (The drivers for my old Connect3d radeon 9000 did NOT support this resolution) however 1280x1024 is just fine. This strikes me as odd because monitors still use a 4:3 ratio. A lot of resolutions conform to this 'standard' 640x480 800x600 etc etc. But in the higher range they seem to 'cheat' a lot more. From what I can understand, this would cause a distorted display. This is very true for CRT's but LCD's seem to be heading that way asweel, wich is something I Don't get. I say this because it is always recommended to use an LCD at it's own resolution, wich is the amount of pixels on the substrate. I can hardly imagine that they would produce non 4:3 screens, allthough ofcourse it is possible.
Some more info on this would be greatly appreciated since I could be wrong about this and tell people wrong things : )
P.S. and yes, I know that if your monitor is capable of going up really high in resolution the distortion on lower resolutions should be minimal, nevertheless, it is deffinatly there.
Anonymous User - Thursday, September 4, 2003 - link
Thanks for a very informative article.I have a Samsung 172T and I have to say the image quality is outstanding. I don't play a lot of FPS games, but for varied use including games and video,using DVI, there are no significant motion blur problems. This monitor is head and shoulders above comparable units I've seen, at least for general use. The price of this unit has dropped significantly since I bought mine almost a year ago. (It may be discontinued).
Been an Anandtech reader since 1996. Keep up the great work!
spikemike - Thursday, September 4, 2003 - link
I'm still not sure if you have it quite right, each subpixel can be independently controlled, you can get 16 shades of blue 16 shades of green and 16 shades of red, giving you 12bit color or 4096 total colors, the red blue and green do not depend on each other, red can be full on, blue can be "1/2" on and green can be off. The main problem was the lack of color, slow response times, and the fact that the information would "bleed" into the column, having one off pixel in a whole column of on pixels would decrease the over all brightness of that columnKristopherKubicki - Thursday, September 4, 2003 - link
#33, I clarified the article a little to apply to both the EE folks and just the casual reader ;)Kristopher
spikemike - Thursday, September 4, 2003 - link
oops i meant posts 29 and 30 were mine