---- Graydon <[email protected]> wrote: > On Mon, May 18, 2009 at 09:27:31AM +0100, mike wilson scripsit: > > ---- "P. J. Alling" <[email protected]> wrote: > > > I know that when mounted on my D and DS the 1.7x identifies itself > > > as an A lens, yet it will auto focus, while with normal A lenses the > > > camera won't even turn on the AF motor. So at minimum it lets the > > > camera know it is capable of auto focus even though it's an "A" > > > lens, which if you think about it is either a really neat trick or > > > exceeding simple minded, (or maybe both).. > > > > If I was Pentax, I would have a switch, worked by the screwdriver, > > that turned the AF motor on/off, depending whether the driver was in > > or out of its hole. Maybe a halfturn anyway, to make sure that there > > was no slot to engage to. > > There are some edge cases -- like Tamron adaptall 2 adapters with a > non-auto-focus lens attached to them -- that would make this a rather > unfortunate default.
Why? > > The other part of it is that the camera really, really needs to know the > focal length to auto-focus accurately. > > -- Graydon, who has tried to use focus confirm on the 500 while the > camera still thought it was 800. Not by my understanding of how AF systems work. Is there something different in the K10/20 systems? What they generally do need is a decent amount of light. > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and follow > the directions. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
