The Leica 135mm f/3.4 APO Telyt M Manual Focus Lens the two previous M lenses of the same focal length (f/2.8 and f/4, respectively). The sharpness, contrast and resolving power of this unique lens are impressive, even at full aperture. Other plus points are its modest weight, its handiness, and its ease of operation. And it comes with a built-in sliding lens hood.