Well, 850mm actually as these are with the 1.4x TC on. Went down to my local nature reserve and spent a couple of hours in the only hide thats big enough to photograph from. Unfortunately its quite high up as all hides tend to be so reflections were the name of the game! It was a pretty quite afternoon but as I was walking along the hide from the furthest of the 3 windows back towards the first, this Cormorant came up from under the water right in front of me! He was far too close for 850mm and he cuaght me off gaurd so I had to pretty much hand hold this to get a couple of shots off before he dived again looking for fish. It was all over in seconds and he never came close again! And this Duck was having a rest, fairly ordinary shot but I really liked the colours of the water around him as the far off tree's and blue sky gave a nice split tone to the image.