The FE 100-400MM F4.5-5.6 is an E mount lens so it will work full frame with an A7. F - full frame, E - E mount, G Master so the highest optical quality. I use mine on both A7RII and A9. For wildlife photography, especially birds, think about investing in the 1.4 teleconverter. In a pinch one can switch from full frame to APS-C but then one drops the resolution to ~24 megapixels. Check the Sony web site for more information: www.sony.com/electronics/lenses/t/camera-lenses www.sony.com/electronics/camera-lenses/sel100400gm then "Go to Support page"