Pentax KX KX Manual - Page 32

OPEN-APERTURE OR STOP-DOWN METERING Open-aperture SMC Pentax lenses have a diaphragm coupling lever e on the back of the lens which locks into the camera body to permit open-aperture metering. The super telephotos do not have a diaphragm coupler, so they must be used with the stop-down metering system. Use of the Auto-Extension Tube Set K permits open-aperture metering. It can also be set to stop down the diaphragm automatically. Use of other K Series accessories - standard Extension Tube Set K, Helicoid Extension Tube K, AutoBellows K and Bellows Unit K - requires stopdown metering. Whenever any one of these is used between the camera body and an SMC Pentax lens, the stop-down metering system must be used. OPEN-APERTURE METERING LENSES SMC Pentax Fish-eye 17mm SMC Pentax 15mm SMC Pentax 20mm SMC Pentax 24mm SMC Pentax 28mm SMC Pentax 35mm SMC Pentax 35mm SMC Pentax 50mm SMC Pentax 50mm SMC Pentax 55mm SMC Pentax 85mm SMC Pentax 105mm SMC Pentax 120mm SMC Pentax 135mm SMC Pentax 135mm SMC Pentax 150mm SMC Pentax 200mm SMC Pentax 300mm SMC Pentax Zoom 45 - 125mm SMC Pentax Zoom 85 - 210mm SMC Pentax Macro 50mm SMC Pentax Macro 100mm f/4 f/3.5 f/4 f/3.5 f/3.5 f/2 f/3.5 f/1.2 f/1.4 f/1.8 f/1.8 f/2.8 f/2.8 f/2.5 f/3.5 f/4 f/4 f/4 f/4 f/4.5 f/4 f/4 STOP-DOWN METERING LENSES SMC Pentax SMC Pentax SMC Pentax SMC Pentax Zoom 400mm 500mm 1000mm 135 - 600mm f/5.6 f/4.5 f/8 f/6.7 30.