OK, weather was overcast but I had to get out to test my new lens. Sigma 500mm F4.5 EX APO HSM, and the Bogen 3421 gimbal head. Thoughts about the lens. 1 Heavy. 2 Focus speed seems as good as my 70-200 VR, even in low light. 3 CA seems fine. 4 For some reason, the Sigma rear lens cap does not fit on my Nikon lenses. Either wont go all the way on or will not rotate to lock. 5 Did I mention heavy. 6 Cropability, See the shots below. Most of these are a 50% to 70% crop. 7 Works just fine with the Bogen head. I had to attach the plate at the most forward holes in order to balance with my D2X. QUESTION For those having one of these lenses, does yours have a small amount of play just ahead of the drop in filter area? Mine does. Most of these shots are ISO 800 in order to get the shutter speed up. Most are around F6.3 to F8, and cropped a lot, some around 70%. The EXIF info is in the file if you are using something like Opanda iExif. I did make a pass through NeatImage to clean up the noise a little. These below are only cropped vertically I believe I like this lens! Although did I mention it is heavy? And takes up 1/2 of my big Lowepro hiking pack.