Sigma's DG lenses are optimized for digital SLR cameras, who typically have a CMOS sensor smaller than a film camera's 35mm frame. The optical construction of the 105mm macro lens is made of 11 elements in 10 groups without any special elements, and features 8 aperture blades. The lens provides a maximum magnification of a 1:1 ratio with a minimum focus distance of 0.313 meters (A 1:1 ratio means that the image on 35mm film is the exact same size at real-life, which translates to huge magnification when viewed on your computer screen at 75dpi). The lens is rather compact compared to other macro lenses with a size of 74x97mm and weighing 460 grams (although the length grows substantially when focusing towards closer subjects). The lens also features an infinity focus, so it can be used for taking portraits or other fixed-length shots.



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