I stand by those examples, but I agree there is an issue with sub-pixel sampling artifacts that make the technique not quite as ideal as I'd like it to be, and also because it does pick up the difference in sharpness as well as resolution which exaggerates the difference. It's not a perfect method, but what you see is, for all practical purposes, a confirmation of existing observations. You need to know what you are looking for, and what is an artifact - as you rightly pointed out.
Life of Pi, iTunes 1080p has more detail than 720p. Here's a good old fashioned mega-blow-up with forensic levels of sharpening applied. There's simply more to the 1080p image, you can see the soft edges from the 720p version that show up in the difference graphics. Case closed.
Edited by imagic - 3/4/13 at 11:53am