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02-11-2010, 07:37 AM   #1
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Pentax 300mm/f4 compatible teleconverters

Hi,

Does anyone have experiences of Sigma EX 1.4x APO DG teleconverter with Pentax smc DA* 300mm f/4.0 ED (IF) SDM lens and K20D?Any problems with autofocus?What about Kenko 1.4x?Or are there any other compatible converters available that will (not should) work?
Thanks a lot for your comments/help in advance!

02-11-2010, 11:52 AM   #2
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QuoteOriginally posted by kamis68 Quote
Hi,

Does anyone have experiences of Sigma EX 1.4x APO DG teleconverter with Pentax smc DA* 300mm f/4.0 ED (IF) SDM lens and K20D?Any problems with autofocus?What about Kenko 1.4x?Or are there any other compatible converters available that will (not should) work?
Thanks a lot for your comments/help in advance!
Hi Kamis,

I use a Tamron 1.4X Pz-AF MC4 with the DA*300 and find it quite acceptable: it does keep the AF and everything else, coupled with the K20D and the K7. One thing I do find is that it hunts a bit but that is easily taken care of because of the lens QuickShift feature which allows for more latitude in focusing. That very much helps me to avoid too much hunting with the TC.

I am also told that the hard-to-find Pentax F- 1.7X AF Adapter works quite well with your set up. I am waiting for mine to come in, so I can't really give you reviews. All I know is that it is a very good product.

No idea about the Kenko 1.4X.

JP
02-11-2010, 12:14 PM   #3
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QuoteOriginally posted by kamis68 Quote
Hi,

Does anyone have experiences of Sigma EX 1.4x APO DG teleconverter with Pentax smc DA* 300mm f/4.0 ED (IF) SDM lens and K20D?Any problems with autofocus?What about Kenko 1.4x?Or are there any other compatible converters available that will (not should) work?
Thanks a lot for your comments/help in advance!
the sigma teleconverter is probably NOT compatible with the DA 300 F4 due to the fact that the front element of the sigma TCs extends into the rear of the lens.,

You need a recess at the rear of the lens 35mm in diameter 14 mm deep to accept the sigma TC

aside from that the sigma TCs do not support SDM so you would be MF only, assuiming it mounts at all.

Aside from older TCs that were initially released for the Power Zoom lenses in the early 1990's, you can also use the SMC-F 1.7x AF TC. This will not drive SDM or even the lenses own screw drive, but the TC does have its own focusing elements, therefore providing a limited range of AF once you manually focus close to the correct distance
02-11-2010, 01:25 PM   #4
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Thanks JP and Lowell for these useful informations.

02-12-2010, 09:19 AM   #5
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The Pentax 1.7x works very well with the 300mm
02-12-2010, 06:47 PM   #6
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QuoteOriginally posted by Mike.P® Quote
The Pentax 1.7x works very well with the 300mm
Very nice to report this, Mike.
I am anxiously waiting for my deal (for that adapter) to be completed. Should be very soon.

JP
02-12-2010, 06:51 PM   #7
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I agree with JP & MikeP. I have both the Tamron 1.4X Pz-AF MC4 and Pentax AF 1.7x. Both work quite well with the DA*300mm.
02-14-2010, 05:40 AM   #8
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Hi again,

Thanks a lot for these new comments.I would like to buy either Tamron 1.4X Pz-AF MC4 or Pentax AF 1.7x,but I'm afraid that they are not available here in Finland.Anyone knows where could I try to order/buy one?A new one,if possible...Thanks for the info in advance !

03-14-2010, 06:22 AM   #9
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Hi again,

I have planned to buy Pentax AF.17X tc ,but the I was informed by the seller that the tc he is selling is "F series vintage" and does not support SDM...But is this "vintage tc" compatible with DA*300 at all...?He couldn't promise that this is compatible with DA* lenses..Does anyone have experiencies of this "vintage" tc with DA* lenses? I'm not expecting AF to work ,but is there a risk of damaging the lens?Thanks!
03-14-2010, 07:19 AM   #10
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Heres an old thread with lots of info on teleconverters. It was started mostly for the Tamron 1.4 but has info on many other converters also.
A lot of folks have had good luck with the Kenko pz-af shq 1.5 also which may or may not be easier to find and may cost a bit less.
Anyway, just read the thead and see for yourself.

Tamron TC

My opinion though is if you can find the Tamron MC4 1.4x get it.

Last edited by OrenMc; 03-14-2010 at 11:05 AM.
03-14-2010, 09:00 AM   #11
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QuoteOriginally posted by kamis68 Quote
Hi again,

I have planned to buy Pentax AF.17X tc ,but the I was informed by the seller that the tc he is selling is "F series vintage" and does not support SDM...But is this "vintage tc" compatible with DA*300 at all...?He couldn't promise that this is compatible with DA* lenses..Does anyone have experiencies of this "vintage" tc with DA* lenses? I'm not expecting AF to work ,but is there a risk of damaging the lens?Thanks!
It will not damage the lens and AF will work (not SDM) as the teleconverter itself does the autofocusing my moving elements inside.
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