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05-05-2013, 11:25 AM   #1
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Join Date: Mar 2008
Location: placerville, ca
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Autofocus extension tube ~18mm

Hi All--
As you all know, no one makes an auto-focus extension tube for Pentax cameras. I have "gutted" a number of 2x AF teleconverters most of which have yielded an AF extension tube of about 25mm. I have done this with AF teleconverters that cost from almost nothing to about the edge of what you don't want to fiddle with. (The trick is to find an AF TC the glass element retention rings of which have notches in them allowing for the use of a spanner wrench to remove the glass.)
I have not been able to find a 1.4x AF TC with the proper retention rings that was affordable.
The other day I found the Vivitar Series 1 1.4x AF TC for $99.00.
The photos I could find did not show a notched retention ring on one side, and there were no photos of the other side.
Vivitar's response to my inquiry was boilerplate--"Not recommended--Waranty voided" kind of stuff.
B&H did not have a sample handy that they could look at to tell me if any of the retention rings were notched.
So, I took a gamble and bought one anyway.
NO NOTCH IN THE RETENTION RINGS--either of 'em! Dirty Razza Fratz!!!
But with just $99 invested, I decided to take a stab at it any way.
Here is how to do it:
On the male end of the TC there is a black metal ring held in place with three screws. Unscrew 'em.
Now you will be able to see two tiny notches in the ring. My spanner wrench would not work--your won't either in all likelihood.
Do not give up!
I got a pair of pliers, gently gripped the metal housing the glass elements, and gave it a gentle twist. VOILA!!! Out it came!!!
Reassemble and I now have an AF extension tube of about 18mm.
Good luck with this new toy.
If anyone has any use for the "guts" of this once teleconverter, let me know. You cover the postage, and it is yours.

Last edited by pntxjack; 05-05-2013 at 11:28 AM. Reason: spelling

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