5 Common Defects in Your New LCD TV or Monitor (Warning: Cannot Unsee!)

How To Spot 5 Common Defects in Your LCD (Warning: Cannot Unsee!)

Color banding, backlight bleed and the dreaded dead pixel — here's what to avoid when making your next purchase.

By Matt Braga

As the saying goes, what has been seen cannot be unseen. It's a rule that applies to solar eclipses, Spiderman 3 and, perhaps most frighteningly, LCD monitor defects. So while you might be enamored with your fancy new flatscreen, there could be a score of problems lying in wait that you've yet to even notice.

We're talking color banding, backlight bleed and the dreaded dead pixel — things you might not even notice if you don't know where to look. While living with these problems is more than possible, they mark the difference between high-end and lower-cost screens.

Thus, if you're looking for a new LCD — or perhaps you'd just like to see how your own model stacks up — here are some defects you might be able to recognize, and hopefully avoid when purchasing your next flat-panel display.

Color Banding

This defect is harder to notice during casual use, but its the bane of graphic designers and photographers alike. Instead of a smooth transition from one color to the next — as you might expect from a sunny blue sky — a viewer can make out individual strips, or bands of color, that compose an image. This is all due to a difference in color depth. Most decent monitors will use an 8-Bit color depth, capable of displaying 16.7 million possible colors. Less expensive, or older panels, however, may only display 16.2 million colors — an insignificant difference, perhaps, but enough to cause the bands you see on-screen.

To see how your display compares to the best, observe the simple gradient test above. All monitors display very slight, subtle banding, but the worst offenders will appear blocky, and immediately recognizable.

Dead Pixels

No one likes dead pixels, the sort that stare back at you with the unblinking blackness of the eye of Sauron. Dramatic, perhaps, but it could also be an indicator of more serious problems with your screen. Most manufacturers consider a few dead pixels to be acceptable during the manufacturing process, but finding ten or more on-screen — especially in clumps — could mean it's time to break out the warranty.

Luckily, checking for dead spots isn't that difficult, and you might even be able to spot some while reading this. With something like the LCD Dead Pixel Test, you can cycle through red, green, blue and white images that should help you identify any trouble spots that might not be apparent during regular use. It's normal for an older model to have a few dead pixels scattered about, but a new model should have almost none.

Clouding

This problem appears exactly as the name implies. Poor manufacturing processes or designs can place stress upon an LCD panel, just enough that it no longer sits perfectly flat on-top of the display's backlight. The result is that, in certain parts of the screen, light is shining off-center ever-so slightly — just enough to cause a cloudy, or less brightly-lit portion of the screen.

To test for the presence of clouding on your own display, turn off your lights, turn on your screen, but leave it unplugged from a video source. The blank screen should immediately show any hotspots, similar to the image above.

Color Gamut and Temperature Differences

Unless you're dealing with color-sensitive work, most users will be none the wiser to issues with temperature and color gamut. With some cheap TN-based panels, colors may appear with a blue or yellow tint when compared to more expensive IPS displays. This is the result of a poorly manufactured backlight, which can color the screen in unforeseen ways.

If you haven't already noticed a problem on your current screen, then you're probably fine. However, the easiest way to know for sure is to load the previous mentioned Dead Pixel Test. A white test screen should appear...well, white. If there's any yellow, blue or even a slight green tint, then hardware and software calibration may help offset the difference and produce a more usable looking screen.

Backlight Bleeding

Unfortunately, backlight bleeding is present on most LCDs produced today, but the extent to which it becomes visible largely depends on the type of screen you buy. Ideally, the LCD panel is supposed to block the backlight, allowing light to pass only through the pixels of the screen. However, blocking this light completely isn't always possible, the result being a certain degree of leakage, or bleeding, around the sides of the panel.

You can usually identify bleeding via bright spots of light on the edges of a display, which are most evident in dark or low-light situations. As you test for clouding, any bleeding of the backlight should also be obvious as well.

What sort of criteria do you keep in mind when buying a new LCD panel? Have you had any issues with past displays? Let us know in the comments.

Images via Flickr user tom.hensel, p_valdivieso, mufoxe, and avforums.com