I have the Canon 17mm f4 that is great. No noticeable vignetting, sharp with good color contrast. I have not noticed flare or chromatic aberration in any of the pics I have shot with this lens so the coating must be excellent. As a point of comparison, I used the 16-35 f2.8 L for my EOS extensively for over 8 years and this FD lens has not left me wanting.