i, ii, iii

Canon Lens Class and Technology Abbreviations - Roman numerals in the lens name describe the lens’ generation. For example, there are two Canon 24-70mm f/2.8L lenses: the first one is the Canon EF 24-70mm f/2.8L USM, and the other one is Canon EF 24-70mm f/2.8L II USM. The only difference in the name of the lenses is the “II” designation of the second lens, which means it is the newer, updated version. Both are professional, tough L-grade lenses, but with different optics and price. Generally, if a lens gains IS which is Image Stabilization it drops the previous numeral and should be considered a newer release.