Just a warning, the 21 and 27" imacs have a much bigger problem with screen persistence than previous models.

I am just now finishing fixing up a 21" imac that got persistence while left over the weekend doing a wireless test. This happens when you disable screen sleep, screen dim, and have brightness set high, for a period of >12 hrs. Even rotating desktop pictures won't save you, it'll burn in the dock, menubar, desktop icons, and clock (on screensaver) too.

It's only visible when viewing a medium brightness image, such as a solid color or grey, or greyish desktop pattern/picture. The persistence is not visible on flat white or black.

None of the "fixing" programs I tried are effective, some of them can make it worse. Nor are the directions on apple's web site on the issue. The correct method is thus:

1. Get something on your screen that is some flat black and some flat white. Use regional screen capture (apple-shift-4 and select) to create two images, one solid black and one solid white. Image size is unimportant.

2. Make a folder "BW" on your desktop and move both images into that folder

3. Open energysaver and set display to not sleep and not dim

4. Open desktop/screensaver and set screensaver to start in 3 minutes (this is IMPORTANT) Select "Choose Folder" on the left and select the BW folder on your desktop

5. select the left of the three display styles. Click Options and select to Crop images, disable crop images, and disable clock. (all IMPORTANT)

6. close options and select Hot Corners and designate upper right to start screen saver

7. open displays sys prefs and turn brightness all the way up

close sys prefs and move mouse to upper right to start it.


I got bit by not setting the screensaver to turn on. Despite having unplugged the usb keyboard after starting it, sometime after I left for the weekend it popped out of screensaver for unknown reasons, and stayed there because timed screensaver was disabled. So come Monday the original image was cleared, only to be replaced with a persistent image of the screensaver prefs!

It takes about 48 hrs to clear heavy persistence. Be sure to set things back to normal after you are done. In particular step 3.


I work for the Department of Redundancy Department