Samsung PL64E8000GFXZP - Manual (Page 217)

Use this function when there are after
images or symbols on the screen,
especially when you displayed a still
image on the screen for a long time.
N The after-image removal function
has to be executed for a long time
(approximately 1 hour) to effectively
remove after-images on the screen.
If the after-image is not removed
after you apply the function, repeat
the function again.