I just looked up the photozone test report. This is one paragraph from their "VERDICT" of the lens. http://www.photozone...-tokina162828ff
"Unfortunately there may be a hair spoiling the (optical) soup here - quality control. As mentioned we purchased three lens samples for testing, two in Nikon and on in Canon mount, and all three showed some centering issues. The initial Nikon variant was so poor that we had to cancel the testing procedure. The second sample, used for this review, was better, but still suffered from slight decentering at the long end."