Shallow Thoughts

Akkana's Musings on Open Source, Science, and Nature.

Sat, 28 Mar 2009

LCD Burn-In, er, "Image Persistence"

Mostly, I love my Dell 2005FPW S_IPS monitor. Nice colors, sharp image, incredibly w ide viewing angles. But one thing made me uneasy: while working on a smooth gradient in GIMP, I noticed some funky pixels in the bottom right of the screen, where I could see horizontal bars where the image clearly didn't have them. And if I moved the image, the bars stayed put. Oh no! My lovely monitor maybe wasn't so lovely!

Since then I've been pretending not to notice (I bought the monitor used, so warranty return isn't an option). But yesterday, I maximized Firefox on a page with a medium cyan background -- and that barred area was a lot worse.

In fact, it was so much worse that I could see detail in it: it was my xchat window. I could even read some of the menubar items.

It's an LCD! They don't get burn-in ... do they?

Well, yes, it turns out, they do. Only it's not called "burn-in", it's called "image persistence". And for some people, it happens very quickly, while other people never see it. Anecdotally S-IPS monitors seem to show image persistence a lot more easily than TN monitors, but nobody seems to know why.

The good news is that it's temporary -- it's not permanent burn-in like old CRTs sometimes showed. The solutions most people suggest:

On my monitor, about an hour and a half of all-white made it better, and after turning it off overnight, the next morning I could no longer see any trace of the persistent image.
Update two days later: Strangely enough, although the pattern seemed completely gone the next morning, that evening it returned, even though I hadn't had any window at all in that space all day. I gave it another hour or two of all-white over that area, then its usual evening of rest, and the next day it was gone again and stayed gone this time. At least, it's evening now and it hasn't returned yet.

So I guess I need to change my habits. I already use power saving mode so the screen sleeps when I'm not there (no screensaver); but on the other hand I'm at the machine day and night, and I like to keep windows in the same place.

How do you invert the screen? You'd think there would be a gazillion programs to do that on X, but there aren't. You can compile a C program called sgamma then run sgamma -b -1 to invert, and sgamma -b 1 to restore. It restores to full brightness, though, so if you've changed your brightness using a program like xbrightness you'll have to adjust it again afterward. Alternately, Guillermo showed me a nice little C program called invgamma, by Ben Winslow, that just inverts whatever gamma curve you already have (run it again to undo the effects). Ben doesn't seem to have a page for it and it doesn't have any license info in it so I can't put it on my site either, but if you google for it you'll probably find a copy.

I'm a trifle bummed that the whizzy S-IPS monitor turned out to be so delicate. But I suppose it's good to change habits now and then anyway and not get too stuck on particular window positions. Maybe it'll help keep my brain from burn-in too.



I wrote an update, 6 months later, with more details: LCD monitor burn-in, revisited.

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[ 11:21 Mar 28, 2009    More tech | permalink to this entry ]