This lens is the Leaf Shutter (LS) 165mm lens for Pentax. Without the LS lens, the shutter sync on the Pentax 67 is around 1/15th or 1/30th of a second.
The LS mode allows using high-speed flash sync with a shutter speed ranging between 1/30 ~ 1/500 sec. When shooting in this mode, “U/S” lever on the lens should be set to the “U” position for “Usual” mode and the camera’s shutter speed dial to 1/8 sec or less while the leaf shutter dial – to the desired speed. Next, the leaf shutter needs to be cocked and an X-sync cable connected to the flash terminal of the lens for high-speed sync. It is crucial to cock the leaf shutter before each shot. Otherwise, only the camera shutter will be fired, probably at 1/8 sec or slower, depending on your camera’s settings, and the lens will function as an ordinary lens.
The Pentax 67 is a SLR medium format system film camera for 120 and 220 film, producing images on the film nominally 6 cm by 7 cm in size, made by Pentax.
The Pentax 6×7 has a dual bayonet lens mount, and a wide range of interchangeable Takumar and later SMC Pentax 67-designated lenses exist. More than forty years after the original camera introduction a wide selection of lenses is still available, together with the latest Pentax 67II variant.