Color shift could occur in ultrawide lenses. I frequently use a Tokina 12-24/4 on snow, and at the shortest focal lenght the corners could turn to light cyan in cloudy and diffused light. Tokina aren't the only to be affected by that, anyway.
regards
Vitantonio Dell'Orto
www.exuviaphoto.com
www.sarnavandrarhem.com
Vitantonio Dell'Orto
www.exuviaphoto.com
www.sarnavandrarhem.com