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09-24-2008, 11:46 AM   #1
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tamron 300/2.8 + adaptall 2 PK/A + pentax 1.7X AF

Does someone know if a tamron 300/2.8 + adaptall 2 PK/A + pentax 1.7X AF will autofocus?
No point between adaptall 2 PK/A and the 1.7X AF?
Thanks for your answers.

09-24-2008, 01:37 PM   #2
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QuoteOriginally posted by Djteddy Quote
Does someone know if a tamron 300/2.8 + adaptall 2 PK/A + pentax 1.7X AF will autofocus?
No point between adaptall 2 PK/A and the 1.7X AF?
Thanks for your answers.

I have (and use) this combination and autofocus is fast. Autofocus will be only with the central focus point. I'll post some pictures tonight. I like this combo a lot, however it will regularly show purple fringing.

09-24-2008, 04:06 PM   #3
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I also wonder the IQ between Tamron 300/2.8 + original tamron adaptall 2 teleconverter and Tamron 300/2.8 + Pentax 2X-AS teleconverter, any big differences in IQ?

Last edited by dsport; 09-24-2008 at 05:34 PM.
09-24-2008, 04:18 PM   #4
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My experience is like David's, My 1.7x afa adds fringing if conditions are right (branches against cloudy sky etc.) unless I stop down a couple of stops f10 or so (probably f5.6 on the lens) Focus works great, here is a sample at f11

09-24-2008, 07:38 PM   #5
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Here are some pics, all taken with tamron 300/2.8 (60B) + adaptall 2 PK/A + pentax TC 1.7X AF:

I also used the Tamron adaptall 2X TC with the 300/2.8. I felt quality was good, but I really did not like to always remove the adaptall - PKA adapter from the 300/2.8, put the TC, put the adapter on the TC, put the combo on the camera... and then change for another TC... that's why I got the Pentax 2X-AS TC. I did not do extensive testing or comparison, but the quality of this TC looks very good, probably better than the Tamron TC...
09-25-2008, 03:12 AM   #6
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Original Poster
Thanks for your comments and pics.
so no problem with autofocus.
Last question: will AF function with PK adaptall 2 and not PK/A adaptall 2?
I think so but I'm not sure.
The difference between the 2 adaptalls is just the A: Aperture on DSLR and not the AF function?

Last edited by Djteddy; 09-25-2008 at 04:29 AM.
09-25-2008, 05:43 AM   #7
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I looked at a tamron 300 F2.8 but don't know what version I looked at.

I elected NOT to buy it because the copy I looked at had serious PF witht he AF Adaptor, and would only go to F4 withg the KA mount attached, not F2.8.

I had read somewhere that early adaptors would not permit faster than F4.

As a result, I still use my SMC 300 F4. and the 1.7x AFTC.

Note, I see comments that people report AF still works with the 300 F2.8 plus 2x Tamron TC plus the 1.7x AF TC. WHile I can't dispute what people report, all I can advise is that personally, with three different AF bodies (PZ-1, *istD, and K10D) I have NEVER been able to get the AF TC to work on a lens (or combination of lens and TC) slower than F4. You have to remember that pentax only ever gauranteed this adaptor to work with F2.8 and faster lenses any way
09-25-2008, 06:33 AM   #8
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I don't have the PKA adapter. I have the PK adapter.

It works pretty good. With chromatic aberrations as others have mentioned. And it weighs a ton.

09-25-2008, 10:54 AM   #9
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I got rid of my 1.7x TC to fund my K20D purchase, but I used it on the Tamron with good results. As others have reported, it makes PF worse unless you stop way down. AF was VERY snappy. Never tried anything other than the center focus, though.

I have stacked the 1.7x with Tamron's 1.4x and still had autofocus. The results were pretty good.

The Tamron paired with the Tamron 1.4x (the new one) is quite good, very sharp and I have not noticed any addition PF problems.

I have also used the Tamron with an older Vivitar 2x TC. The combo produced fairly good results, a little soft but certainly good enough for web postings.

I think I posted some photos with the Tamron 1.4x and the Vivitar 2x a couple of months ago...

Oh, the lens worked great with the 1.7x and the PK/A adapter. My adapter is a little flaky, though, so I'm not sure if it works with the Tamron 1.4x TC...

Last edited by dkittle; 09-25-2008 at 10:55 AM. Reason: more details
09-25-2008, 12:13 PM   #10
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I tried the Tamron 60B with the AF adaptor once and it works easily, as the others have written. For max. image quality I prefer the Pentax A TCs 1.4x-L and 2x-L. The 2x-L is by far(!) the best 2x tc I have ever used and I have a good collection of those. The 2x-S will also work, but image quality will be noticeably (though not severely) degraded.

Purple fringing is a slight problem with the 60B, even when used on its own. But on the other hand sharpness and contrast of this old lens is still very, very good, even on the K20.


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