The hunt for dead pixels

A friend got a new plasma HDTV and asked me to help him spot dead pixels. Without a video diagnostics disc, the easiest way is to hook up a notebook to the TV and set the desktop wallpaper to a solid color.

In the past, I only checked black and white screens. Black is to spot stuck pixels, and white is to spot dead pixels.

Stuck pixels are very annoying, so there should not be any at all. Luckily, they are easy to spot. I've never seen stuck pixels on a new display, though.

In theory, checking the white screen for dead pixels is sufficient because as long as any of the RGB sub-pixels are not working, it won't show up as white. While this is true, it turns out that white is the hardest to check. I have never caught a dead pixel without knowing where it was.

Online wisdom is to check the R, G and B components separately. For completeness, I also check Cyan (G-B), Magenta (R-B) and Yellow (R-G).

Checking individual components is easier than white. It is either the color or black. Even so, it is not easy to spot a dead pixel. You have to scan the screen at a nose's length away. (But once you spotted one, you can see it from 1-2 metres away.) A plasma screen makes it harder due to its inherent noise.

After 45 minutes — 1920 x 1080 is a lot of pixels — I spotted one fully dead red pixel and two partially dead blue and red pixels. I thought the dead red pixel was a dead RGB pixel, but the macro photo showed that it was just the red pixel.

There are three levels of severity:

• Fully dead RGB pixel: obvious (relatively speaking), but also very rare.
• Single dead sub-pixel: not obvious, but once you found it, you can spot it again easily (within 2 metres).
• Partially dead sub-pixel: hard to find even though you know where it is

The dead pixels are all at the peripheral, so I recommend to my friend to keep his unit. I also decided to do him a favour by not telling him the location of the dead pixels.

(My own LCD TV has one fully dead pixel and several partially dead pixels. The dead pixel is an eye sore — if I look at it. The other dead pixels are not noticeable. I missed all of them until I saw the dead pixel by chance a few months after I got the TV. )

The hunt for dead pixels