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Old Mar 15, 2006, 6:04 AM   #11
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Errno_Gmm

Does it degrade your lens image quality? or justnot have AF capability?

Al
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Old Mar 15, 2006, 7:59 AM   #12
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Ricehigh is correct about the contacts on the Vivitar. I have the Pentax AF-1,7x converter and it works great with fairly fast lenses, but does not have the image quality of the Pentax 1.4X-S converter.

Remember the Pentax AF-1,7x converter has limited AF and will not AF throughout the entire focus range of lenses at one time.

Tom
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Old Mar 15, 2006, 9:59 AM   #13
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look at it this if you get a bad one. do as i did. i had an OLD albinar 2x that i never used as it really was a POS, but, it is meter coupled like the K&M series lenses. i took the glass out of it and now i have a meter coupled 25mm extension tube. works great w/my 50mm f1.4 as a macro lense.

roy
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Old Mar 15, 2006, 10:53 AM   #14
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I got my Pentax SMC-A 2X S converter from e-bay for 1000 SEK (125 USD) including P&P from Germany. As you can see in the moonshot thread it was really worth it, and I think the 1,4 TCs (SMC-A) from Pentax are just as good. But have anyone had the opportunity to compare the A-converters (4 different, high quality, high price) with the AF 1,7 converter, which is just half the price (new, from Pentax Sweden). Do you sacrifice a lot in sharpness for the AF?

Kjell
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Old Mar 15, 2006, 12:55 PM   #15
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I have a Takumar-A 2X converter, I have used it very successfully with my non-A-series MF lenses (I have no A-series lenses) but I have not tested it with my F, FA or DA lenses. I will try it out with my Takumar-F zoom, one of my FA zooms and the kit lens to see if it works. This is a Pentax (Asahi Optical) designed and manufactured converter, it just has a simpler optical design and no SMC coating. Anyone else have any experience with it?

The moon picture I posted here http://www.stevesforums.com/forums/v...mp;forum_id=80 was shot with the converter and a Rikenon 135mm.

Ira
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Old Mar 16, 2006, 3:13 AM   #16
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Rice High, again an informative link and explains a lot.

But my simple question to all is which make or type of 1.7x or 2x tele-converter will give me some AF and AE metering? The Pentax, the Tamron, the takumar?

Currently when I connect my new AF lenses onto the converter, I lose all Av settings and obviously AF too.

I would like a converter that will allow my lenses to continue to operate normally with AE and if possible AF.

AL
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Old Mar 16, 2006, 7:54 AM   #17
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> Rice High, again an informative link and explains a lot.

Thanks. Actually, I do always hope to update my pages to include more info and make more accurate descriptions but personally I have not much spare time left. :-(

> But my simple question to all is which make or type of 1.7x or 2x tele-converter will give me some AF and AE metering? The Pentax, the Tamron, the takumar?

In short, current line of AF tele-convertor from Kenko, Tamron and Sigma works fine. The Kenko and Tamron are believed to be the same OEM product(s) but they have the best compatibility owing to there is no protruding lens element in the convertor front.

The Kenko design is clever as it is a "pass-through" design which pass all the lens contact data directly between the original lens and the body. The aperture value will not be re-calculated, e.g. a 100/2.8 AF lens will still be a 2.8 lens. Metering still be correct as the convertor can just be seen as a strong filter which cut 3/4 of the incoming light for a 2X convertor, for example.

With the Pentax 1.7X AF convertor, it converts also the aperture value by 1.7X. Metering is also correct as the body will see a lens 1.7X slower, e.g. a 135/2 lens will become a 230/3.4 lens and when the body choose the converted aperture, everything will be correct again!

> Currently when I connect my new AF lenses onto the converter, I lose all Av settings and obviously AF too.

Noted that the 1.7X is not a true AF convertor, it does the AF inside the convertor. Thus, it has a limited range of AF depending on the focusing position of the original lens. On the other hand, the true AF converters let the original AF lens to do the AF by itself. Depending on the original lens (whether it is a AF or a MF one), you can decide what to choose. However, the availability of the 1.7X is very rare and you must have good luck to find one, with mint condition and at a reasonable price.

> I would like a converter that will allow my lenses to continue to operate normally with AE and if possible AF.

I think your choice are only limited down to the true AF convertor mentioned above and the Pentax F 1.7X tele AF-convertor (not AF tele-convertor :-)), for your above requirements.

Hope this helps.

RiceHigh
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Old Mar 16, 2006, 9:46 AM   #18
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My Takumar-A teleconverter uses all functions except (obviously) auto focus. I would assume (dangerous concept) that all Pentax A-series teleconverters (Takumar, Pentax, SMC Pentax) would also preserve the auto aperture metering.

As for its optical quality, Takumar A-seriesK-mount glass is not known for being particularly good (except for a few that are just Pentax lenses without the SMC), this teleconverter looksmuch likethe Vivitar shown above andproduces "adequate" results. (BTW I owned a Kenko K-mount once, it wasn't quite as good as the Takumar).

Ira
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Old Mar 16, 2006, 10:03 PM   #19
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So exactly which converter does allow AE and limited AF.

I did a quick check of Kenko on Ebay and looked at the MC, MC6, MC7 and AF models, none have contacts for the AE or the AF.

I found this Tamron on Ebay, does anyone have this one? Does it do what they say, AE and AF?

http://cgi.ebay.com.au/Tamron-F-AF-T...QQcmdZViewItem

It gets annoying when you stick your nice new lens on with a tele-converter and the Av on the lcd screen on the Dl displays "--" .
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Old Mar 17, 2006, 5:13 AM   #20
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Crashman, I have the 1.4 version of this converter, and it performs AE and fullAF functions on my Ds with thelike enabled lenses (F, FA, and Tamron AF) that I own.

Lou
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