That I couldn't tell you. 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).. I do know that the
A contacts only give a rough approximation of the minimum and maximum
apertures. The 1.7x will convert those values to the "correct" 1.7x
apertures. It won't correct for focal length in a zoom, or for variable
apertures in zoom lenses, because it can't.
There is one possibility I can think of. If the K20D is on when you
mount the lens/adapter the adapter is powering up as it's being
attached, electronics at startup can send some wonkie signals so the
K20D could be getting something it thinks is focal length information,
but I really couldn't say that it's a error in camera or lens, its an
error in most electronics. You should check the files in Pentax Photo
Lab, the EXIF information will tell you what Focal Length the, (and
lens), camera thought was attached. Maybe the latest version of
Photoshop CS does as well, I don't have that so I don't know, but
nothing /I/ have except the Pentax software will give me the values for
every EXIF field,
Joseph McAllister wrote:
Then that's an error on the part of Pentax, isn't it? Unless the AF
1.7x passes "something" the K20, which it in turn would incorrectly
interpret as "something else", then the lens focal length screen
should pop up and allow you to put in the combo's focal length. Yes?
On May 17, 2009, at 17:10 , P. J. Alling wrote:
The K20D can't get anything from the A*300 or any other lens if
mounted using the AF 1.7x, there's no pass through for the digital
pin. There's no digital pin on the A*300 in any case. Now the AF
1.7x might be supplying some kind of focal length information but it
would be erroneous, since it has no idea what the focal length of the
mounted lens is either, (the A contacts don't pass that information).
Joseph McAllister wrote:
This might be why my K20 did not ask the focal length of my A* 300
ƒ4 when attached to the AF 1.7x tc. It should have, but perhaps it
DID get something from the 300 as to focal length. Of course, the
photos were soft on tripod, so maybe I should have gone to the
Custom Functions and forced a 500mm reading. (There was camera
movement, as the tripod was not my sturdiest)
On May 17, 2009, at 12:14 , Adam Maas wrote:
but also impractical to
evaluate all F and later lenses (A and earlier lenses don't identify
the model to the camera and therefore couldn't support the feature
in-camera)
Joseph McAllister
pentax...@mac.com
http://gallery.me.com/jomac
http://web.me.com/jomac/show.me/Blog/Blog.html
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