What brightness settings do you use? I've been getting eye strain on my 21.5" iMac (256GB SSD) even with brightness down to 3 or 4 "white blocks". I researched it and apparently the LED panel uses pulse modulation which is likely causing my eye strain. Yet my edge-lit LED LCD HDTV does not cause eye strain at all on lower settings I tried using the Shades app and turning the LED to max brightness to avoid the pulse modulation but it doesn't look as good, the max backlight is evident in dark screens. I even tried the SuperCal app and that didn't do much. EDIT: I've also tried adjusting the gamma, white balance, and other contrast settings also. I'm past the 14 day return period. Any way Apple would let me refund or exchange for an older iMac with CCFL lighting? Or is selling it privately my only option?