I'm using a customized Pro Photo theme, and I'm trying to use your plugin to build retina versions of all my photos. It seems to be working great (creating retina versions of the smaller sizes of photos, and letting me know when an original isn't big enough to create a large size retina version).
I read through some of the other posts, and got some ideas (even if they don't solve my original problem). I went into settings>media and changed my "large" size to constrain to 850/850; I (pre-retina) always upload images that are sized 850px in one direction.
SO, my question/problem is: I want my large size to be 850px, for the retina version I would need to upload an image that is 1700px in one direction, correct?
At 72dpi, a 1700px image is larger than 2M... wordpress wont let me upload. How is everybody uploading larger images in order to create retina versions?