The Sigma 28mm EX-DG-Asp-Macro-f/1.8 AF Lens has been designed keeping the high demands of the industry in mind.The maximum aperture of the lens is equal to f1.8The lens construction includes 10 elements in 9 different groupsThe f stop range is from f1.8-f22  and the angle of view is 75.4°The filter size of the lens is 77mmThe lens’ reproduction ratio is 1:2.9Some of the features of this Sigma wide angle lens include fixing extra light, control aberrations, and automate focusingThe closest focusing distance of this Sigma 28mm F/1.8 Lens is 7.9 inches and the full extended length is 3.5 inches