I recently replaced my old Canon 75-300 EF 4-5.6 IS Lens with the new model, a Canon 70-300 EF 4-5.6 IS Lens. I have always liked my 75-300 and although it is a less than perfect lens, I've always considered it the best for money. However, not long after I bought it, the IS switch quit working and the IS could not be turned off. This didn't effect me greatly, except I couldn't use it on a tripod, but since with IS I seldom use a tripod any more, I just lived with the problem.

However, with the release and positive reivews of the 70-300mm lens I've been interested in getting one, which I just did now that the original bug in the lens has been fixed (unsharp image at full telephoto when shot in portrait aspect). While the 70-300 is very similar to the 75-300 and retains all the qualities of the earlier model that I like so well, all the shortcomings of that lens have either been completely removed or improved to the point they are no longer significant. The 75-300 was a very good lens for the money, the 70-300 is a great lens for the money.

I did some preliminary unscientific tests of the lens to makes sure everything was working, but the first test I've done under more or less controlled conditions was to see how the IS worked when the camera was on a tripod (I’ve been in the mood lately to do very low light shooting). I'd heard mixed opinions about whether the new and improved IS in this lens needed to be shut off or not during tripod usage. I repeated my test of this several times and got the same result each time. As can be seen even in the thumbnails below, having the IS on while the camera is mounted on a tripod significantly degrades the image.