it adds the seventh contact for digital information to the KA-mount. KAF3-mount The KAF3-mount is used on Pentax lenses that solely rely on SDM or DC autofocus motors. It is identical to the KAF2, but lacks the screw-drive autofocus drive shaft. Another way of looking at it is that it adds the power zoom/in-lens autofocus motor contacts to the KA2 mount. KAF4-mount The KAF4-mount was introduced in June 2016 with the HD Pentax-DA 55-300mm F4.5-6.3 ED PLM WR RE lens. It is identical with KAF3, apart from the missing aperture control lever. Instead, aperture control information is transmitted digitally through the data pin and the aperture is stopped down through a motor built into the lens. It also introduced a new type of autofocus motor, designated PLM or Pulse Motor. At the time of its introduction, the following Pentax DSLR bodies were compatible with the new mount: K-70, K-50, K-S2, K-S1, K-1, K-3 II, with all but the K-70 requiring a firmware update. Also after a recent firmware update the original K3 can use the new mount. “Partially fully-enabled” K-mount All digital K-mount Pentax SLR bodies as well as some lower-end film cameras lack the ability to read the position of the aperture simulator. This means that lenses that lack the lens information contacts introduced with the KA-mount (Pentax K- and M-series lenses as well as some third-party products) do not support open-aperture metering on these bodies. Instead, stop-down metering must be carried out by pushing the “green button” on the camera before taking a shot. This variation of the mount is commonly referred to as the “Partially fully-enabled“ K-mount. R-K-mount The R-K-mount is a variation on the original K-mount by Ricoh. It supports Ricoh's own implementation of shutter priority and auto exposure modes, similar to the KA-mount but much simpler. The only addition to the original K-mount is a small pin, commonly dubbed Ricoh pin, at the bottom which tells the body when the aperture ring has been set to the "P" setting (similar to the "A" setting on Pentax KA lenses). The 'P' setting is not compatible with the 'A' setting as the 'P' pin is in a different location than the 'A' contact on Pentax 'A' lenses and the flange on Pentax bodies. The R-K-mount is used on Rikenon P lenses, Ricoh bodies that include the letter 'P' in their model number, and some non-Ricoh lenses. It