I don't know. I wish the Tokina would have performed well. It's built like a tank, and I liked the constant f/2.8 aperture. However, if it won't focus correctly, it's useless to me. There's a possibility that the lens doesn't play well with the 50D (practically the newest camera at the time). They might have even corrected the issue by now. All I Know is that two separate copies performed terribly in my hands. After returning the second Tokina, I purchased the Canon 10-22 f/3.5-4.5. It's worked flawlessly and given me images I absolutely love.