Quaz51 has figured out that Gran Turismo 5 isn't truly 1080p (runs in 1280x1080) as it uses some clever upscale trickery by repeating pixels in an anamophic picture to 1920x1080. So in theory it is 50% upscaled which is supposedly even less than GT HD. To quote:

GT5 prologue demo is 1280x1080p (yamauchi know than in car game the vertical resolution is the most important for the visibility) but with MSAA 2x now ! it's a very good Compromise.

They also very Improved the display of grills and electric wires and aliasing problems (compare electric wires in GT-HD and in this demo, it's big big gap), the texture filtering is very clean and the HDR ligthing is awesome! all this in 60fps with 16 photorealistics cars, it's Impressive!

The show room and the pit/garage is full 1920x1080 no AA.

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