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How do I check for dead, stuck pixels

A

ahurtt

Diamond Member
So I am going to go out and buy a new (my first) LCD monitor soon and I have heard you are supposed to ask them to take it out of the box so you can check it for dead or stuck pixels before you buy it and take it home. So what exactly is the best way to go about doing this? What exactly is the difference between a dead pixel and a stuck pixel? What does one look like as opposed to the other? What exactly am I looking for before I buy that monitor? What is the best methodology for checking these things in the store before buying? Thanks in advance for your input!
 
I use Dead Pixel Buddy to look for bad pixels. I think the difference between stuck and dead pixels are, a dead pixel will never change, it will always be bad. A stuck pixel you can sometimes rub the LCD screen and it will fade away(sometimes).

edit: You may not be able to run this software in the store, if they dont want you to. See if they will let you change the background on the computer to different solid colors, and look for a single dot that is different. For example, if you pull up a blue screen, and you see a green dot that will not go away, that is probably a dead pixel.
 
Yeah chances are they won't have dead pixel buddy in the store so I can't use that to check before I buy. So I am mainly interested in effective ways of spotting these bad pixels by eyeballing without missing something.

Incase anyone cares I am thinking of a 19" Samsung 930B. It will be primarily for 3D gaming.
 
I wish monitor makers would test for these beforehand and sell them for a cheaper price. Judging by these forums, half of LCDs are sent back to Dell.
 
If you want to make sure that they still do this, you could try calling 1-800-SAMSUNG and see what they say. I work for Acer America, and if we get in a customer LCD with 1 dead pixel, we replace it.
 
Dead pixel = black spot on the screen no matter what (pixel 'off' constantly)

Stuck pixel = red/blue/green spot on the screen (pixel 'on' constantly)
 
The best way is to power it on and have it warm up first. Ideally you'd warm it up for a couple of weeks (to make sure the components are fully warm and give some use to the panel), but as the store probably won't let you do that, a couple minutes or so is probably the best you'll get. Then use a red screen, then green screen, then blue screen, to see if you have any dark pixels in those respective colors. Lastly, use a black screen to check for any bright pixels.

Bright pixels for the black screen are somewhat easy to tell. Dark pixels in the colored screens are harder. You simply can't scan too fast, or your eyes will miss the black dot in all that green. So take small strips to scan (i usually divide the monitor into 10 rows to scan) and take your time, since you're the one paying for the monitor.

What is a dead pixel or a stuck pixel differs by person, there's no set definition. I personally consider any type of sub-pixel defect (a better term for these things) to be a dead pixel, since manufacturers will try to split those definitions in order to offer a good number for their policy (i.e. "we allow zero dead pixels" but define dead = dark, so you're still stuck with bright pixels). So to me dead and stuck are interchangeable -- or at least should be. There's no technical definition of either; I can point to manufacturers that use different definitions. Each manufacturer uses their own terms to define defects, and many don't even use the term "dead pixels" at all, but other things like "pixel defects". However, pay attention to how a manufacturer defines them, so that you know what you're in for beforehand.

Regarding the Forbes article, note the end of the first paragraph. That's right, South Korea only. For its U.S. policy, you can find it at:

http://erms.samsungusa.com/customer/sea...1&AT_ID=5608&PROD_SUB_ID=28&PROD_ID=-1

"The minimum number of defective pixels we allow before we will replace an in warranty monitor is as follows:

For a 15" Monitor - 7 or more bad pixels
For 17" and 19" Monitors -10 or more bad pixels
For 21" - 24" Monitors - 17 or more bad pixels.

For questions or the replacement procedure, please contact our Customer Care Center at 1-800-SAMSUNG (1-800-726-7864)."

I'm assuming that they'll replace a monitor for "customer service" before that limit of 10 bad pixels is reached.

Funny you should mention Acer. They have a very convoluted phrasing for their policy:

"The Limited Warranty does not extend to minor defects of LCD displays occurring in Products equipped with LCD display technology provided that there shall not be more than four (4) defective pixels per million pixels on a given LCD Display, and provided further that, if the display panel is divided into nine (9) equal rectangular areas, there shall be one defective pixel in the central area of the display."

I don't know why Acer can't simply say "we allow a maximum of 4 defective pixels per million pixels, and a maximum of 1 in the center of the screen, as defined in the picture below" or something along those lines (does the phrasing mean that you must have one and exactly one dead pixel in the center for it to count?). Actually the main sticking point I have with Acer's is how they defined things: if you go to that page, and look to the right of the monitor image, it says that for SXGA (17" and 19" monitors), they consider it to have 3932160 overall pixels. Putting that together with the 4 defective pixels per million pixels actually means 15 dead pixels allowed. Is this what Acer is really saying? I hope not but it's the only definition of "pixel" that I see on that page (yes, manufacturers define "pixel" differently too; beware if they define it as an RGB sub-pixel set, then say they only allow 2 or whatever, since dead pixels happen on a sub-pixel basis; the problem here is different though).

Anyway, are we allowed to quote you on the one dead pixel thing? Hehhehheh.

Edit: I forgot to give the link to Acer's policy. It is located at:

http://www.acerpanam.com/synapse/forms/...ral=1&words=All&keywords=pixel&pupv=pu
 
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