Last week at the Space Coast Birding and Wildlife festival I had the opportunity to briefly try out a pre-production unit.  The lens was one of the first pre-production units and a lot has changed since it's manufacture.  The final units will be way better in image quality, performance and handling.  With that said, I will say I was truly impressed with the way the lens performed.The Leica 100-400mm is an f/4-6.3 telephoto zoom lens that gives the equivalent of 200-800mm in 35mm equivalence.The lens has a lockable zoom pull feature, so you can pull the end of the zoom to set the zoom position, or when it is locked, you need to rotate the zoom ring to vary the focal length. The lens has Power Optical Image Stabilization, and high-speed 240fps AF drive, which makes it incredibly fast in focusing performance. It is also, splash and dust proof.A feature I found most useful was the lens collar and foot that also rotates all the lens function switches. This allows you to easily access these in any orientation, landscape or portrait.In thumbnail view, hover over the thumbnail to see the focal length and exposure details.  To see a larger rendition of this slide show please click here