I’ve posted an entry about this in the past but now it seems that David Pogue has done a full-fledged “Pepsi-Challenge” on the topic….
Anyway, we ran the test for about 45 minutes. Dozens of people stopped to take the test; a little crowd gathered. About 95 percent of the volunteers gave up, announcing that there was no possible way to tell the difference, even when mashing their faces right up against the prints. A handful of them attempted guesses—but were wrong. Only one person correctly ranked the prints in megapixel order, although (a) she was a photography professor, and (b) I believe she just got lucky.
I’m telling you, there was NO DIFFERENCE.