There's an extra contact on F and later lenses that is for digital communication between the lens and body. The A contacts only transmit max and min aperture info via the contacts, F and later lenses transmit focal length, current aperture and MTF data (FA and later for MTF) via the digital communication pin. This requires a a small amount of power.
-Adam Bob Sullivan wrote: > It's those little bumps on the lens mount that make the electrical > contact for reading info from the lens. Turn the aperture from f22 to > 'A' and watch the last bump in the series move up 1 mm - contact! If > you don't have 'A' set, you don't need the chip's mtf info. > Regards, Bob S. > > On 12/4/06, Stan Halpin <[EMAIL PROTECTED]> wrote: >> F series and later "transmit" MTF and other info to the body. The >> assumption is that the transmission requires power of some sort. >> >> stan >> >> On Dec 5, 2006, at 12:07 AM, John Celio wrote: >> >>>> Anyone got any theories on how F and later series lenses are powered? >>> What are you talking about? The only lenses I can think of that would >>> need >>> any power are the Power Zoom and (future) supersonic focusing lenses, >>> both >>> of which have those two special contacts just inside the lens mount for >>> providing power from the camera body. Otherwise, all other lenses are >>> driven by the camera's AF motor. Is there something else that would >>> need >>> power? >>> >>> John >>> >>> -- >>> http://www.neovenator.com >>> http://www.cafepress.com/neovenatorphoto >>> >>> >>> >>> -- >>> PDML Pentax-Discuss Mail List >>> [email protected] >>> http://pdml.net/mailman/listinfo/pdml_pdml.net >>> >> >> -- >> PDML Pentax-Discuss Mail List >> [email protected] >> http://pdml.net/mailman/listinfo/pdml_pdml.net >> > -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
