Leica 135mm F3.4 Apo-Telyt M A Best 135mm Lens ever produced Originally designed for Military Applications Apochromatic Correction and Highly Corrected for Infinity Very Sharp & Contrasty   5 Elements in 4 Groups Apochromatic Correction Filter Size is 49mm Apertures from F3.4 to F22 with Half clickstops Focuses from 1.5 Meters to Infinity Built In Lens Hood Superb Image Quality throughout the Aperture Range Great for Scenics/Landscapes and Portraiture