Retina MacBook Pro = Burry images on websites?

It's not a matter of perception… there is no way to make an image 1 pixel : 1 pixel on the iPad 3 in Safari. It is always being up-sampled. Even if you put in the progressive jpg hack Safari will still make it whatever size it likes. Maybe I'm wrong but can anyone show me how to get pixels mapped 1:1 in Safari on the iPad 3? If you can't then how can images posted on this site and others that are meant to show the sharpness of a lens for example ever going going to be useful?

That's the rub though… if you could get them mapped 1:1 they wound be tiny on the iPad 3 and Retina MacBook Pro screens. I bring this up because I spend a lot of my time on photography related sites and have found the experience less than great on the iPad 3 because of Apple's automatic image interpolation.

I'm not saying they're wrong to do it… for most people it's the best option but for photographers I think it might be a step backwards.