The Tamron SP designation is reserved for lenses developed with special emphasis on extraordinary photographic performance. Engineers are free to innovate in an uncommon atmosphere where optical performance comes before price, resulting in lenses that satisfy the demands of discerning photographers. High resolution full-frame digital SLRs demand the optical quality for which the SP 28-75mm F/2.8 XR Di is famous, another in Tamron's selection of fast and constant F2.8 maximum aperture optics, its speed benefits photographers in several ways, including the ability to render cluttered backgrounds well out of focus, added low-light shooting freedom and a brighter viewfinder image. It is featuring XR (Extra Refractive Index) and LD (Low Dispersion) glass in an optical formula employing 16 elements and 14 groups - assuring sharpness, optimal contrast and color accuracy, rendering striking images. Sophisticated aspherical element design and internal focus contribute to barrel size that belies a typically large F2.8 optic. With both an ideal picture angle range, fast aperture and outstanding optical properties, it's no wonder that so many SP 28-75mm F/2.8 lenses can be found in the bags of noted wedding and corporate shooters. Tamron Di lenses are performance optimized for digital SLR cameras and usable with DSLRs featuring sensors commonly referred to as APS-C, measuring approximately 24 mm x 16 mm, as well as larger full frame sensors and 35 mm film SLRs.