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Old Nov 25, 2009, 3:28 PM   #1
JLB
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Default Tele converter as extension tubes

I have read about removing the glass from a teleconverter and using it as an extension tube. Some accounts have not been successful in dismantling the converter and some have broken the glass to remove it. I have a Vivitar with the PK-A/R mount and would like to make it an extension tube. Has anyone here had experience with doing this? Can it be done and maintain the contacts so Pentax-A would be maintained? It would be nice to be able to use it with my A lenses with all contacts working. Please give me the benefit
of your experiences. My other choice would be to get real extension tubes but I really want to maintain the A contacts and tubes with these are hard to find. Thanks for your advice.
John
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Old Nov 25, 2009, 6:48 PM   #2
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Never done it on a "A" converter but on most "M" converters it is quite easy to remove the lens elements. Just requires removing three or four small screws and remove the lens element. On the "A" ones you need to be mindful of the contacts and wires if any.
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Old Nov 26, 2009, 7:48 AM   #3
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The contacts are spring loaded, and must be removed very carefully. Once the screws are removed from the contact plate, it should be lifted off vertically. The aperture coupling mechanism also has a spring which needs to be disconnected - IIRC, after the plate is loose.
I have seen extension tube sets on the auction site listed as fully AF compatible, and seem to remember they aren't any more expensive than a good TC. That is the way I would probably go unless I was just in the mood to fiddle with stuff.
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Old Nov 26, 2009, 1:44 PM   #4
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With my 2x converter (with AF etc) I just unscrewed the glass from the top (not the bayonet end) and it now acts as an extension tube with full contacts
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Old Nov 27, 2009, 6:05 PM   #5
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Thanks for the input. I think I will go for the real extension tubes. Just have to find some with the contacts.
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Old Nov 27, 2009, 7:12 PM   #6
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i came up with the idea and some here have used it. i had to get the hammer as i could not get the TC/ET out..
1 thing you need to consider is cost..
M42= $15-20
K mount with linkage =$20-100
PK -A=$40-125
AF/auto AP $130-400
i use the K/M. you usually have to take only one ex value per shot. that is until you switch subjects
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