The Sony NEX-7 (and now the A7r) has turned out to be a perfect platform. While I haven't yet converted a A7r (since beginning to write this I have sent a A7r to Life Pixel for conversion) I have experimented at great length with using various lens; much the same as I'm now doing with the NEX-7 IR camera. Both of these systems offer a platform where one can have either a 25 or 36 megapixel camera and use a huge assortment of lens from Sony to Canon, Nikon, Leica and so forth. My personal experience has been using Sony, Rokinon, and Mamiya/Phase One medium format lens; and in each case getting excellent results. I'm of the opinion now that you can put just about any lens on either the NEX-7 or A7r and get great image files.
First you need to understand that a camera (any camera) "sees" better than the human eye. In low light our eyes are less sensitive to color than normal; in brighter light the opposite occurs. In short, the human eye is constantly adjusting to the environment. Not so with a camera sensor. A camera sensor always has the same sensitivity. All this before we go into focal length, f/stops, and ISO. A long exposure photograph will bring out objects that are normally faint to the eye while short exposure will freeze action that the eye simply can't. This is before we even begin a discussion to infrared photography.
My history of capturing IR began in the late 60's early 70's using film. I found IR film expensive and very difficult to use. You needed complete darkness to both load and unload the film and finding a proper place to develop was a huge hassle. Eastman-Kodak changed the world of photography as we know it when they introduced a digital camera in the mid 1970's. While the first successful photograph was made by Nicéphore Niépce in 1816, it took another 159 years for the first digital camera to be offered. The first digital camera weighted 8 pounds (3.6 kg), recorded black and white images to a compact disk tape with a resolution of 0.01 megapixels and took 23 seconds to capture the image.