[andybak]

I've always been vaguely aware that JPEG gives better results at a constant quality setting as increase the size of the image.

Firstly - the 8x8 blocks become smaller relative to the image but in addition to this I think that the it's just in the nature of compression algorithms in general and lossy compression in particular to produce better results when there's more source material to work with.

However I didn't expect it to improve enough to enable one to but the Gordian knot that Retina displays have forced upon us by using 2x resolution images across the board.

I would imagine that not all source images respond quite as well as others.

Also - using 2x images for all devices will surely create a quadrupling of RAM requirements which might cause performance issues.

[Retric]

Honestly, I did not notice any JPEG artifacts on any of those images, so I don't think it's that obvious yet.