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PENTAX Auto Extension Tube Set K

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4 27,283 Thu March 5, 2015
Recommended By Average Price Average User Rating
100% of reviewers $80.00 8.00
PENTAX Auto Extension Tube Set K

Set of 12mm, 19mm, and 26mm extension tubes in PENTAX K-mount. Comes with a leather case.

This set has coupling for the aperture stop down lever. With cameras with a full-function K mount, metering can be be done with open aperture. On a DSLR, only "Green Button" stop down metering is available.

Lenses with an "A" setting must be used off the "A" setting since these tubes have no lens information contacts.

Lenses without an aperture ring will be stopped down to their smallest aperture during exposure.

Focusing is to be done manually, also with autofocus lenses.
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Loyal Site Supportaxian

Registered: September, 2013
Location: Texas
Posts: 486

1 user found this helpful
Review Date: March 5, 2015 I can recommend this item: Yes | Price: $70.00 | Rating: 8 

Pros: build quality
Cons: no data pins.

The physical build quality of these is far better than any of the 3rd party equivalents I've used. On the down side, they do not have any contacts to transmit lens data.
Not much I can add that hasn't been covered by others.

Registered: August, 2008
Location: Wellington, New Zealand
Posts: 10,018

3 users found this helpful
Review Date: March 8, 2011 I can recommend this item: Yes | Price: None indicated | Rating: 8 

Pros: enable wide open focusing
Cons: require lenses with aperture ring, no f-stop recorded

The only thing "auto" about these extension tubes is that they allow wide open focusing without requiring you to change the aperture manually back and forth. There are cheaper “non-auto” tubes available without the aperture lever but these are as manual as it gets. Photographers intending to use the tubes with Takumar preset lenses, may not take issue with that and hence wouldn’t need these “Auto” version.

If you want to be able to use a lens without an aperture ring (e.g., the superb Sigma 70/2.8 EX Macro) then you'll either have to forget about these tubes and use PK/A tubes or always shoot the lens at the smallest aperture possible. The latter is not an entirely stupid proposition as a 1:1 macro on extension tubes will have a ridiculously shallow depth of field so stopping down to at least f/11 is pretty much a must and from there it is not far to f/22 (the smallest aperture on the Sigma 70/2.8 EX Macro).

In principle, it is possible to modify these tubes into PK/A tubes so that they fit the aperture range of a particular lens you want to use with them. The description of K-mount contacts and some DIY talent are all you need. However, while the contacts that tell the camera about the aperture range of your lens are relatively easy to create, it takes a lot of craft to create a working “A”-pin. The latter needs to be spring-loaded so that it makes contact with a slightly indented contact on the mount.

Hence an easier way to obtain a PK/A extension tube is to remove all the lens elements from a PK/A teleconverter. Most 2x TC are not that brilliant anyhow and might be put to better use by converting them into PK/A extension tubes. This may even add AF abilities, but frankly this is not a feature that will be terribly useful when doing macro photography.
Site Supporter

Registered: October, 2008
Location: Vancouver, Canada
Posts: 6,013
Review Date: July 6, 2010 I can recommend this item: Yes | Price: $90.00 | Rating: 8 

Pros: Maintains the lenses Automatic Diaphragm.
Cons: Diaphragm mechanism becomes sticky, stacking tubes makes it worse.

I only really use the No. 3 tube (26mm) for my K50/4 Macro lens, so I can get 1:1 magnification with a single tube.

The Auto extension tube set works well and maintains the full aperture metering mechanism of the attached lens.

The only issue with this extension tube set, which applies to all the “auto” versions, is that the diaphragm mechanism becomes sticky and makes it hard to turn the aperture dial on the lens. This issue gets worse when you use multiple tubes at the same time. A good CLA by Eric will solve this issue.

I have two sets and the average price was $90.00.
A mint set with box, case and manual cost $110.00.
An excellent condition set with case and manual cost $70.00.
Site Supporter

Registered: July, 2008
Location: Dartmouth, Nova Scotia
Posts: 3,948

1 user found this helpful
Review Date: May 9, 2010 I can recommend this item: Yes | Price: $80.00 | Rating: 8 

Pros: Exceptional construction quality
Cons: Hard to find, expensive

These are what they are, and they work very well to vary focal length for macro or close-up work. Just a nice addition to any kit for the shooter who wants versatility.
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