Having owned his lens for about three months I was almost set to sell it on after obtaining consistently soft and very poor quality images. I had installed a quality Hoya pro 1 digital uv filter on the day I had purchased the lens to protect my investment. It turns out this was destroying image quality!!!! Having removed it the quality is superb and I am so pleased with this lens. Wide open at 400mm it's perfectly acceptable but with good light stopped down to f8 it's razor sharp!! I am beginning to wander if some of the negative comments on this lens, in particular the softness of its images are due to it not favouring the use of filters? With the filter removed my lens is literally transformed. If you are looking for a quality versatile lens with image stabilisation (which in my opinion is very effective) do not hesitate to buy this lens. I had a 400mm 5.6 l and I find the 100-400 far more suited to my needs. Due to the IS I find it excellent to use as a walk about lens and easy to handhold and a perfect companion for my canon 7d.