For those frustrated with Preview as a default viewer for images, check out LilyView. I had missed it initially when I got my riMac, but if you use "actual size" in LilyView, or command-0, you get the image in 1:1 pixels on your retina screen. it is kinda like quicklook in that you get just the image, but it does much more. You can shoot through tons of photos via the arrow key, it's hyper fast. And mouse over and you get photo info. And it has an "edit in..." menu feature so you can fire up your favorite image editing applicaton right from within LilyView. It is a great bit of software that does one thing really well.