Description: Pentax makes two Leaf Shutter lenses for their 645 camera system, the 75mm f/2.8 and 135mm f/4 LS lenses. They incorporate a leaf-shutter unit with faster flash sync speeds (1/500, 1/250, 1/125 and 1/60 sec). In the leaf-shutter mode, the cameras focal plane shutter is set at 1/8 second, and the programmed auto and manual flash operation is possible through the X-sync (PC) terminal located on the camera body. TTL/OTF flash metering is NOT possible with the leaf-shutter lenses. The 75mm f/2.8 and 135mm f/4 LS lenses can be used as standard lenses in the Aperture-Priority AE and Manual modes.