Telephoto lens series pentax da lens mount pentax k lens speed 24 focal length 70 mm construction prime lens area of use portrait photography night photography action photography focus manual focus auto focus af motor no internal af motor circular aperture closest focusing distance 70 cm focal length equivalent to 35mm camera 107 mm lens construction groupselements 56 number of aperture blades 9 minimum aperture 22 max aperture 24 lens swit