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Screens without blemish

CTX promises LCD monitor with no dead pixels

LCD manufacturer CTX is guaranteeing that its new LCD S530 screen contains no dead pixels. The catch? The promise only lasts 101 days.

LCD screens are made up of rows and columns of pixels that combine to create text and images onscreen. Each pixel has three separate subpixels (red, green and blue) that allow an image to be viewed in full colour. The subpixels' transistors turn them on or off depending on whether they are needed to create the image.

There are millions of subpixels within each display. In most LCD screens an odd transistor will not work correctly and will appear to be off when it should be on. These are known as dead pixels and, until now, almost all LCD screens sold have contained one or two. Producing a screen in which every single pixel functioned would be prohibitively expensive.

In spring last year, the ISO 13406-2 standard was set to address this issue. LCD screens are now described as belonging to one of three classes: class 1, class 2 or class 3. Only class 1 allows for no imperfections.

Most LCD monitors conform to class 2 or 3. CTX's newly announced S530 monitor is the only product on the market that appears to conform to the class 1 standard and to be priced as if it were a less costly class 2 model.

"Many screens are perfect when first purchased. It’s guaranteeing the product won't develop dead pixels that's the hard part," said Iiyama senior support engineer Ian Thompson.

The problem with LCD screens is that their pixel quality can only be checked once the panel has been assembled, meaning each screen that doesn't comply to the no dead pixel promise would have to be scrapped, costing the manufacturer and therefore the consumer more money.

"There is a price premium on the product. However, we have kept this to a minimum," said CTX's marketing manager Ben Levinson.

"Most companies already manufacture 'perfect' screens and then sell on those that aren't, so it shouldn't really be any more costly to the manufacturer," added Thompson.

Despite CTX's claims that dead pixels "have caused serious consternation among consumers", Iiyama, which complies with the class 2 standard, claims it has received no such complaints.

"Generally, if there were a few dead pixels users wouldn't even notice," said Thompson. "We never receive complaints about dead pixels, but then we do not comply to the class 1 standard."

However, visitors to PC Advisor's discussion forum are concerned about buying LCD screens for that very reason.
"I am almost at the point of buying a TFT but the one thing that held me back is the dead pixel issue," said reader Djohn.

Other forum contributors have experienced the dead pixel issue first hand.

"My own monitor arrived pixel-perfect on arrival but later developed one dead pixel and then, six or so months later, a dead sub-pixel," said forum member Spook Tooth.

"I can live with one or two dead pixels provided they are out of sight, so to speak. What would please me more than just having no dead pixels on arrival is a reasonable guarantee that none were expected to develop during its lifetime," he added.


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