I have owned a 100-400mm lens for a few years now. I used it mainly for bird shots both static and flight along with the Canon 20D. The main problem that I found with it was that it would give a faint outline that was slightly offset from the main subject. Zoomed out this manifested itself as the image always being soft. I beat myself up thinking that it was just inexperience on my part. I tried all different combinations of shutter speed and F-stops but I could never seem to get the sharpness in the photos that I wanted. I ended up going to a 500 F/4 and never looked back as my photos improved drastically.
To make a long story short, I bought a 50D recently and tried the lens out on it hoping that maybe it was my 20D that had the problem. I still get the same results. I can see results from people here on BPN that own the 100-400 and some of them are amazing compared to what I got. Just wondering if any of the folks out there have had similar problems and were able to cure them?
Thanks in advance for your help,