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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