to adapt old M42 lenses without any optical correction or loss of infinity focus/changed close focus distance. Other SLRs with a short flange-focal distance can accept M42 lenses as well: Canon EF-mount (44.00 mm), Sony and (Konica) Minolta A-mount (44.50 mm), Sigma (44 mm), Olympus 4/3rd (38.67 mm), and many more, but notably not Nikon F-mount (46.5 mm). Nikon AI/AIS Optically corrected adapter to use Nikon AIS AI lenses on K-mount. Voigtländer Bessamatic / Kodak Retina Adapter for Voigtländer Bessamatic and Voigtländer Ultramatic lenses, Kodak Retina Reflex, or Kodak Retina IIIs lenses. Petri There are some Petri adapters to K-mount but they do not allow to infinity focus due to the different flange distance. Medium format Pentax made adapters for its medium-format lenses to use on the K-mount, both the 645 and 6×7, and for the Hasselblad Bayonet type. Also there is a Pentacon-Six (Kiev88 CM) adapter still in production and a shift adapter to use Pentacon lenses as shift lens. Pentax 645 Pentax 6×7 Hasselblad Bayonet type Pentacon Six Mamiya 645 T-mount Mounts used for Telescopes, microscopes and generic optics. The T-mount was initially developed by Tamron (1957) to allow the easy adaption of generic 35 mm SLR optics into multiple mounts. The T-mount is a 42 mm diameter 0.75 mm pitch screw mount with a 55 mm flange focal distance. Later versions (T2, T4, TX) were more advanced and complex. Several other manufacturers besides Tamron have used these mounts. Because the T-mount is still used for many telescopes and microscopes, they are still available new. Note that while both T-mount and M42-mount are 42mm screw mount systems, and will mount if they are forced, they are not compatible. The difference in pitch can cause damage to the lens, adapter or camera mount if they are confused. Adaptall These are adaptors designed by Tamron to allow the transfer of aperture setting from lens to camera or vice verse, including the Adapt-A-matic (1969), Adaptall (1973) and Adaptall-2 (1979). When Pentax introduced the KA-mount in 1983 Tamron upgraded their Adaptall-2 K-mount into an Adaptall-2 KA-mount. For more details see the Tamron article or the Adaptall-2 web site. Available adaptors for other cameras to use K-mount Four Thirds (Olympus) Micro Four Thirds (Olympus and Panasonic) Canon EF-mount (EOS) Minolta/Sony A-mount (Sony Alpha) M39 lens mount (Leica) Samsung NX-mount Sony E-mount (NEX) Fujifilm X-mount Cameras Pentax Manual focus K – K2, K2 DMD,