Here's what I can glean from the expanded EXIF from Aperture. All at
ISO 400 with +.5 exp. comp. and 540 flash in HS Sync.
A*300 with AF 1.7x camera turned on after mounting lens combo.
Lens Name. "A Series lens"
Focal length = 0.0mm 35mm focal length= 0.0mm Aperture ƒ6.7
Shutter 1/350th
Same lens combo for next series of frames (did I turn it off then on?)
Lens Name. "A Series Lens"
Focal length = 55.0mm 35mm focal length= 82.0mm Aperture ƒ9.7
Shutter 1/350th
Changed to the DA* 200 with Pentax 2x-S tc leaving camera on, I guess.
Lens Name. "A Series Lens"
Focal length = 55.0mm 35mm focal length= 82.0mm Aperture ƒ6.7
Shutter 1/350th
Took the Pentax 2X-S tc off, remounted the DA*200. Don't know if I
power cycled. Maybe. Changed from shutter priority to 'P'
Lens Name. "smc PENTAX-DA* 200mm F2.8 ED [IF] SDM"
Focal length = 200.0mm 35mm focal length= 300.0mm Aperture ƒ11.0
Shutter 1/180th
On May 17, 2009, at 20:57 , P. J. Alling wrote:
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
Pentaxian
http://gallery.me.com/jomac
http://web.me.com/jomac/show.me/Blog/Blog.html
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