Lens review

Canon EF 70-300 mm f/4-5.6 IS USM

10. Autofocus

I remember that the Sigma 70-300 APO was strongly criticized in this category. In comparison with Sigma, Canon looks better because the sharpness adjustment works faster and quieter. In the absolute scale however these results are very weak since they are way behind what is presented by 70-200 f/4L. Here even the much less expensive Canon 100-300 mm seemed to work smoother and quieter.

The accuracy does not look great either although as opposed to the Sigma 70-300 APO, the Canon "goes crazy" in a bad light situation less often. As far as the accurate shots are concerned the Canon behaves more like Sigma than other USM Canon lenses. In the testing conditions the lens was mistaken as much as 16%. To compare, Sigma was mistaken 21%, Canon 100-300 mm 7.5% and Canon 70-200 f/4L only 4%. Additionally we have an impression that the tested lens has a slight tendency towards front focusing.

In summary, it's clear that the horrible autofocus performance could be the cause of such divergent opinions about the 70-300 mm IS. If somebody in a critical moment is lucky enough to have the sharpness set up correctly, the opinion goes on that it is a terrific lens. If someone is less fortunate to have the sharpness adjusted incorrectly, which nobody is expecting after purchasing a 550$ lens with a USM motor, the negative opinion spreads. Yes, you could say it makes mistakes but not because of its optics, which work perfectly well but because of the autofocus. Here is one piece of advice. When we take an important picture using the Canon 70-300 mm IS we need to take more than one shot. In that case we have more chances that one of them is perfect.