I have been seeing posts about people using lenses made for the Sony APS-C cameras on the A7/A7R and people talking about possibly using the FE glass on the APS-C sensor cameras. Would someone be kind enough to provide a simple explanation of how this works? For example, if using an APS-C lens on the A7, do you have to do anything to get it to work on the camera or do you just put it on and it works but with fewer megapixels? Similarly, how would the lenses for the A7 work on an APS-C? What happens to the relative focal length of the lenses in each case. Sorry for what may be a dumb question. I would just like to get a better sense of it as I see people recommending APS-C lenses be used on full frame and FE lenses for the APS-C cameras and I don't completely understand the process. Thanks.