The first is what I'd expect if you didn't tell the camera what focal
length you were using. So I guess that's right. Of course if I
remember how the K20D is supposed to operate if SR is turned on it
should ask you to input the actual focal length of the lens, so that
could be a problem with the camera. Does it ask for the focal length if
you mount the A*300 without the AF adapter? The second is certainly a
problem since it's assuming a focal length of 55mm and you didn't change
lenses. Maybe the 1.7x adapter identifies itself to the camera as a
55mm lens? Somehow that doesn't seem right either. But the 2x-s
adapter is AFAIK an A type lens mount, it doesn't have a chip so it
couldn't identify itself as anything to the camera, (I could be wrong
about that, I don't own one so I never bothered to check). The DA* 200
was read correctly. Since you're not sure of your procedure perhaps you
could experiment and keep track of the results. That might narrow down
the problem.
Joseph McAllister wrote:
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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