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

By Matthew Braga

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

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. 



Color Banding


 
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


 
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


 
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


 
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