The pentax da 60 250 f4 ed if sdm lens is designed to deliver fantastic optical quality with the inclusion of both super low dispersion and extra low dispersion optical elements ensuring crisp and clear images with minimal abberation throughout the full range special seals mean the lens is dust and moisture resistant while the sp coating on the lens repels dust water and grease to keep your images free from grime with its wide range equivalent to 92 383mm in 35mm terms the pentax da 60