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11-28-2007, 08:05 AM   #1
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extension tubes with aperture?

Are there readily available extension tubes for the k mount that allow aperture priority mode? All the cheap import type ones on ebay seem to indicate that they're manual only.

I think I either misunderstand some of the mechanics involved or I'm confused.

Isn't there supposed to be some sort of lever/prong type thing on the mount?

11-28-2007, 09:43 AM   #2
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There are 4 different types of extension tubes available to my knowledge, these are:

- K mount full manual tubes with no apature coupling between the lens and camera. These will work in stopped down metering mode only, on a DSLR or film cameras

- K mount automatic extension tubes with both the apature coupling and activation levers installed, these will work in manual exposure mode on DSLRs and Apature priority mode on most film bodies that can use the apature ring (i.e. excluding latest film cameras). On DSLRs in AV mode they will only shoot wide open

- KA mount tubes with apature couplings AND the electrical contacts for full apature control on all cameras. These will work with KA mount and newer lenses to give Av mode esposure control on DSLRs

- KAF mount tubes that do all of the above plus have the drive for autofocus lenses. These will work with a DSLR to what ever the capability of the prime lens is.
11-30-2007, 11:42 AM   #3
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ok, I thought there were more options...but all I ever see on ebay, etc seem to be the manual ones you referred to first. Guess I shall keep on looking Thanks
12-02-2007, 02:58 PM   #4
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Ok I seem to be coming up short for sources....can any one recommend where to get a set of tubes that isn't just the manual type on ebay (i.e. no aperture coupling/whatever)

I don't need it to be fully automatic, but can't seem to find anything between the two

12-02-2007, 03:05 PM   #5
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I have the Vivitar Auto Extension tubes, and I am pretty sure that they do.
12-02-2007, 04:02 PM   #6
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I've got a set of Kenko auto extension tubes that allow full auto aperture control. It doesn't do autofocus though. (not a big deal, I dont' use autofocus anyway when using them.)


here's a link to an item at Adorama, but it seems they're out of stock of the Pentax ones right now. I got mine used at keh.com.

AEXTUBEPK Kenko Auto Extension Tube Set for the Pentax AF Mount.
12-03-2007, 07:34 AM   #7
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great, thanks guys, I'll keep an eye out for those models
12-03-2007, 11:06 AM   #8
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Vivitar AT-23

QuoteOriginally posted by jmbower Quote
Ok I seem to be coming up short for sources....can any one recommend where to get a set of tubes that isn't just the manual type on ebay (i.e. no aperture coupling/whatever)

I don't need it to be fully automatic, but can't seem to find anything between the two
Look for the Vivitar AT-23 auto extension tubes. They will allow you to stop down DA lenses with the tubes. You can see the electrical contacts in the photo below. I've used them with the kit lens for fun.



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