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12-29-2006, 11:27 AM   #16
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yes K or KA wont auto focus.. the kenko 1.5 seems a good-ish available cheaper converter.. its only with used stuff on ebay u get the older none autofoucs converters..

trog

12-29-2006, 12:24 PM   #17
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OK, a quick primer on Pentax mounts:
  • M42: 42mm Screw mount. From the 60's and early 70's used with the Spotmatic/SV series cameras. Usable on Pentax DSLRs with an adapter, but in total manual mode.
  • K: The original Pentax Bayonet mount. Does not send signals to the camera body. Manual focus, metering using the stop down method (the Green button on the K10D/istD or the AE-L button on all others.)
  • KA: 2nd generation K mount has contacts that send aperture info to the camera. Maunual focus. Retains all exposure modes on DSLRs.
  • KAF/KAF2: Latest mounts, same as KA, adds auto focus.
Here is a very good everything Pentax reference link:
Bojidar Dimitrov's Pentax K-Mount Equipment Page

Hope this helps.
-Alan
01-09-2007, 08:23 AM   #18
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Any more comments on 2x?

I'd still be interested in more comments on 2x teleconverters.

I realize that the 1.4X ones will give better IQ and faster f/#, but I am in a
situation where I need the longer reach of a 2X TC. My longest good lens
is a Tokina 80-200 AT-X pro f/2.8 zoom (I'm lucky to have it), and I'm planning
to photograph wildlife in Africa this summer (lucky me!).

I'd really like to have a 400mm focal length, and I was wondering about using
a 2X TC on the Tokina. That would reduce the weight and bulk of carrying
another lens as well as the cost / availability issue as well.

Any comments on how well a 2X TC might work with this lens, and any
recommendations for which one to get? I noticed that there is a 4 element
one (Kenko / Tamron, like the 1.4X job) as well as a 7 element one (Kenko).
I've also seen a used 7 element one that is AF but not the latest "DG" version.
Any comments on whether the "DG" designation is a real perfoemance
advantage?

I recently got a Sigma 400mm AF lens (cheap - non-APO) to start taking wildlife
photographs and its contrast and chromatic aberration is unacceptable in a
lot of lighting conditions; I'd like to to better with the Tokina zoom
plus 2X TC. Am I dreaming, or is this realistic?

Any comments much appreciated!

Thanks,

Tom (1st post here, I think)
01-09-2007, 11:41 AM   #19
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i just posted a thread using the 500mm and a tamron AF(it doesn't) mc4 2X. worked pretty good. i've NEVER had good luck with 2X TCs on zoom lenses. too much glass in the way, i guess. this one cost me $10us delivered..

one good use you can get out of a TC is too take the glass out of them and use them as extension rings for macro work.. if they are an A type all the better..

01-09-2007, 02:43 PM   #20
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Pardon my ignorance, but I was under the impression that any TC had to be THE TC for the lens. Somewhere I'd read that if you have
a given make and model of lens, for some reason, there was only the TC that was made specifically for it, if any. If you used, for instance, another make TC, you'd get unacceptible performance.

Is this true?
01-09-2007, 07:13 PM   #21
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QuoteOriginally posted by INcreative Quote
so ok let me get this straight... if a get a k mount... i can't use the auto focus feature on my lens... but if i get a kaf mount then i can use the auto focus feature on my lens???
Well it's actually simpler than that. Unless you get a second hand tc (which I strongly suggest you stay away from other than something like Tom's offer above) than any "K" mount will give you autofocus. Both the Tamron 1.4 and the Kenko 1.4 are reasonably priced, and work well. What most people are talking about when they say K, KA, Kaf mounts, are lenses, not tc's. If you are interested in the different lenses here is a site that will help
Bojidar Dimitrov's Pentax K-Mount Equipment Page

NaCl(hope that helps)H2O
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