Macbook Pro retina 13: why 1280x800 (no HiDPI) looks blurry? I have a macbook pro 2.5Ghz i5 retina 13 inches. I'm running Mountain Lion. When I change the resolution to 1280x800 (no HiDPI) it looks blurry, more blurry than a non-retina 13 inch macbook pro. Why is this? I don't understand this since its 1/2 of the native resolution.

Thanks
Every monitor does better in its native resolution (yours is 2560x1600).
That's because the monitor always "adjusts" (scales the pixels) from the resolution you set to its "native".

For the best clarity you must set the resolution of your system to 2560x1600.