Leica 28-35-50 F4 Tri Elmar Asph. The Zoom lens that is not a Zoom lens. Viewfinder Framelines snap into place when twisting the ring from 28 to 35 to 50mm.  Focal lengths in between cannot be used. Image Quality is the Same as or Better than single focal length Leica lenses.  One compact lens that is like carrying three lenses without ever having to change lenses! 8 Elements in 6 Groups Two Aspheric lens elements Filter Size is 49mm Built in Telescopic Hood Focuses from 1 Meter to Infinity Apertures from F4 to F22 Smaller and Lighter than you Think Leica recommends that you only use Slim Filters with this Lens (all Heliopan) Perfect Wide Open at F4 One of my Personal favorites and a Remarkable piece of Optical Engineering