More info from the same source: "Panasonic Leica 100-400mm f/4.0-6.3 Power OIS and weather sealed zoom lens." So it will likely be at least as fast as the panny 100-300 at 300mm plus, of course, the option to go to 400mm. Weather sealing also suggests it will be a higher end lens, which I think is good--need a higher quality option than the 100-300 for bird photography.
If Olympus ever comes out with their 300mm f4 (plus 1.4 teleconverter), will be a very interesting decision between the two. I'd probably stick with the zoom, inter alia, because I find zooming in and out often helps a lot in finding the bird in the viewfinder, and because I find the lower zoom range useful for insects, et al. But I'd wait to see reviews and see how they compare in weight.
Last edited by Jim M. : Wednesday 15th July 2015 at 22:45.