the lens is at any other setting the pin is retracted and does not make contact. The other five contacts are used to encode the lens's aperture range. Each contact on the lens is either conducting or non-conducting, providing a binary 1 or 0, respectively. Two contacts encode the lens's minimum aperture—, , or ; although no Pentax K-mount lens has ever had an minimum aperture, OEM lenses often have. The other three contacts encode the lens's maximum aperture; their meaning is dependent on the minimum aperture indicated by the lens. (There are at least 2 newer lenses that have a minimum aperture of only f/16: HD D FA 85mm F1.4 and HD D FA* 50mm F1.4. https://www.pentaxforums.com/lensreviews/hd-pentax-d-fa-85mm-f14-sdm-aw.html and https://www.pentaxforums.com/lensreviews/hd-pentax-d-fa-50mm-f14-sdm-aw.html) KAF-mount The KAF-mount was Pentax's second and much improved attempt at adding auto-focus to lenses. It adds a small drive shaft to the KA-mount, allowing the body to adjust the focus of the lens. This makes the lenses less bulky than the earlier KF-mount, which had both a motor and batteries inside the lens. It also adds a seventh electrical contact, this one carrying digital information from the lens to the camera. It carries the following information: focal length, distance to the subject, exact absolute f-stop value, and lens size. This information is used to make better exposure decisions, along with the multi-segmented metering that was introduced in cameras using the KAF-mount. The MZ-30/ZX-30, MZ-50/ZX-50, MZ-60/ZX-60, the *ist series and the K100D/K110D lack the mechanical stop-down coupler/indicator. In these cameras – in aperture priority mode – the aperture is set by a dial on the camera body, and no longer on the lens. Pre-A lenses can only be used in manual stop down metering mode and manual flash mode. KAF2-mount The KAF2-mount is the same as the KAF-mount except that it adds two extra power contacts to the inside of the mounting ring and transmits modulation transfer function (MTF) data through the digital seventh contact. The power contacts were originally used for power zooming. Since the introduction of the K10D digital SLR model, they are mainly used for powering Silent Drive Motor and DC motor lenses. The K10D/K100D Super and later cameras do not have a mechanical stop-down coupler/indicator and thus can only use stop-down metering on pre-A lenses. KA2-mount The KA2 is identical to KAF, but lacks the autofocus drive shaft. Another way of looking at it is that