You can also extract depth information from each cameras lens array. In theory, if you combine that capability on a per camera basis with photogrametric and/or stereo imaging techniques, you should be able to get a fairly refined depth map of a scene passively if the scene is static or you have well synchronized shots. Something I also wanted to explore but never had time to do.

At the time, I always considered passive ranging to be a potentially more valuable feature of lightfield cameras more so than refocusing images.