Nano Crystal coating system ns for increased light transmission and reduced internal Reflections Maximum diameter 3 43 inches 87mm fast F28 maximum aperture closefocusing to 95 inches maximum versatility in all shooting conditions Optimized for excellent optical quality and true ultrawide 106 Degree edge to edge coverage with Canon APSC sensor digital cameras Utilizes 3 high precision 2 aspherical 1 ED Lens elements for superior image quality Inner focusing system if length doesnt change and front element does not rotate keeps integrated petaltype lens hood properly oriented