The Megapixel Myth
kenrockwell.com
kenrockwell.com
But he's right that megapixels aren't the whole story, and beyond a certain level they are irrelevant to typical users.
A nice page on this subject: http://www.wyofoto.com/Digital_Image_Quality/Image_Quality.h... details a plausible way to calculate perceived image quality.
There might have to be some adjustments made because the human eye isn't equally sensitive to all color differences, but this is getting closer to the mark.
I think people should be aware of this.
720p is still less than 1 megapixel, and has more than twice as many pixels as 480p. At such a small megapixel rating, the increase is certainly going to be much more profound than a 4mp to 8mp camera. But, perhaps doubling is a better metric than quadrupling.