Burn In

dwskau's picture

I am working on a data display that is up 24/7. The display goes in the lobby of a building and shows weather data collected from a station on the roof. Because the exact same thing is displayed constantly (with the exception of some changing values) there is a burn-in risk. I have put the entire composition in a 3D Transformation patch that moves very very slowly in the X and Y axis to help prevent this. The problem is that it still stays in a small area of the screen and if I move it too far it doesn't look centered. Does anyone have any experience with preventing burn-in? Are there recommended methods for preventing it? Anyone have any fancy ideas for better ways?

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cwright's picture
burn-in prevention

Moving the image a bit is one way to handle it.

Make sure the contrast is as low as possible on the display, and if it's a plasma display make sure it has at least 150 hours of display time before being deployed (plasma screens burn-in more during their first 150-200 hours of use, since the phosphor is new).

On the software-side, you can try passing the image through some CoreImage filters that perform subtle changes on the image. Adding a bit of low-key noise could help a bit. You can also add periodic animations to the more static portions of the screen, to keep each pixel changing a bit.

You could also do some gamma hacks -- instead of solid 50% gray, use two pixels, one 100% and the other 0% -- then have them switch places. The ratios will be different depending on the display's gamma curve, but it should look ok from a distance. Ideally, this should be done in large blocks (which may not be practical, since large blocks make this more apparent), since burn-in affects regions at a time, not just individual pixels. perhaps scanlines would help here (simple to code in CI)

Or, just use an LCD and do some minor pixel shifting/varying. [note: if you're using an LCD and low-key noise, make sure the noise is a few values higher, since LCD's will usually round off the lowest bit or two.]

dwskau's picture
LCD

The screen is a LCD. That would have been important info to include in the original post I guess. There is also the possibility that this would become the default screensaver for all the machines in the building (all of them have LCDs). Ironically right now the screensaver has a burn-in problem.

Right now the text is mostly white on black. Would something other than the two extremes be better? I can't find a good resource addressing issues of whether some colors are best on LCDs or not and I don't want to be responsible for causing any damage.

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cwright's picture
lcd burn-in

lcd burn-in happens when the LCD liquid gets biased from constant charge. So essentially any non-changing value will slowly bias it over time. I think for LCDs it slowly returns to normal if you stop displaying the burning material, but I'm not certain for modern LCDs. I've heard that even fluctuating a value will help prevent burn-in (so, instead of 100% white, varying from 95% to 100% will keep it from burning in), but I'm not sure I believe that.

You want to avoid full extremes if possible. There aren't any places that tell you that, but there are a bunch that note how having higher contrast accelerates burn-in.

psonice's picture
Simple transition

Instead of worrying about colours, why not just add a simple transition of some sort say every 10 minutes?

The whole screen could flip round in 3d (like a dashboard widget does) or something like that, so the everything on screen gets transitioned to black for half a second or so. That should prevent burn in, won't be too distracting, and avoids the annoyance of things like flickering pixels or slowly shifting screen.

cwright's picture
definitely the way to go

If it's possible, this is definitely the way to go. more pixel variance etc. However, be careful: just as keeping pixels white can burn them in, some LCDs can get black-burn-in too (depending on how their default polarization). The transitions should ideally change every pixels' color.

With the noise solution, the pixels don't need to flicker -- it can be low frequency noise (i.e. slowly changing over time, not necessarily each frame). Or the noise can be shifted around differently from the shift of the background. shrugs

I was also thinking about having periodic black/white bars sweep across from time to time, horizontally or vertically. They could leave a gently fading transparent trail. This would look tasteful, and would keep things changing.

dwskau's picture
Transitions

I like the transitions idea and the idea of something sweeping across the screen. I'll try to find a way to make whatever sweeps relevant to the data. Maybe the color could be tied to the temperature or something similar. The problem with both of these is they would obscure the data temporarily and seem arbitrary(very minor problem because it updates every 30 min and they would be obscured for a split second).

I have also thought about a drop shadow effect that would move through the course of the day like a real shadow. There are several problems with this though. First, the displays aren't always in the same orientation so the shadows would not be lined up with real world shadows. Second, it still wouldn't stop displaying white at the center although it might help some when it is used in addition to the slowly moving solution.

psonice's picture
Quick + easy: cube

If you're after something quick + easy that gets rid of the issue, how about rendering the display onto the surface of a cube. You could render on the front and back faces, and make one side black, the other white. Then just rotate it 180 degrees every 10 minutes, so it alternates between white and black and the pixels are guaranteed to change colour every 20.

dwskau's picture
Thanks!

Thanks for all the input! I implemented a few of the suggestions and as the project evolves a few more might get pulled in.

tobyspark's picture
blast the screen with white overnight

to my understanding, to stop burn-in on an LCD you blast it with white overnight. of course, if its visible 24/7 you can't do that.

toby