EDIT: My code for this is actually open source, if anyone would be able to look and comment.
Things I can think of that might be an issue: using a custom font, using bright green, updating the label too fast?
The repo is: https://github.com/andrewljohnson/StopWatch-of-Gaia
The class for the time label: https://github.com/andrewljohnson/StopWatch-of-Gaia/blob/master/src/SWPTimeLabel.m
The class that runs the timer to update the label: https://github.com/andrewljohnson/StopWatch-of-Gaia/blob/master/src/SWPViewController.m
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My StopWatch app reportedly screen burns a number of iPads, for temporary periods. Does anyone have a suggestion about how I might prevent this screen persistence? Some known workaround to blank the pixels occasionally?
I get emails all the time about it, and you can see numerous reviews here: http://itunes.apple.com/us/app/stopwatch+-timer-for-gym-kitchen/id518178439?mt=8
Apple can not advise me. I sent an email to appreview, and I was told to file a technical support request (DTS). When I filled the DTS, they told me it was not a code issue, and when I further asked for help from DTS, a “senior manager” told me that this was not an issue Apple knew about. He further advised me to file a bug with the Apple Radar bug tracker if I considered it to be a real issue.
I filed the Radar bug a few weeks ago, but it has not been acknowledged. Updated radar link for Apple employees, per commenter’s notes rdar://12173447
It’s not really a “burn in” on a non-CRT display, but there can be an image persistance/retention issue on some LCD display panel types.
One way to avoid both is to very slowly drift your image around, much more slowly than a screen saver. If you move your clock face around a small amount and very slowly (say several minutes to make a full circuit of only a few dozen pixels), the user may not even notice this happening. But this motion will blur all fine lines and sharp edges over time, so even if there is a persistance, the lack of sharp edges will make it harder to see.
Added:
There is also one (unconfirmed) report that flashing pixels at the full frame rate may increase the possibility of this problem. So any in-place text/numeric updates should happen at a more humanly readable pace (say 5 to 10 fps instead of 30 to 60 fps), if repeated for very long periods of time. The app can always update the ending number to a more accurate count if necessary.