Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
09-10-2012, 08:52 AM   #16
Loyal Site Supporter
baro-nite's Avatar

Join Date: Aug 2011
Location: North Carolina, USA
Photos: Gallery | Albums
Posts: 4,364
On an older-style ("uncrippled") K-mount camera or lens there are two levers, the coupling (or stop-down indicator) and the actuator. The actuator is the one that sticks out on the lens; the coupling is harder to see. The coupling tells the camera how many stops down from wide open the lens is set to, and so the camera can correctly meter through the lens. When a lens is mounted on the camera the diaphragm is fully open; only when you press the shutter release does the camera stop down the lens; this is what the actuator is for. (Take a lens with an aperture ring, stop it down, and flip the actuator back and forth and see how it opens and closes the diaphragm.)

The "crippled" K-mount doesn't have the coupling, and this is why fully manual lenses require stop-down metering on bodies with the crippled mount: the camera doesn't know what the aperture ring is set to.

To control the aperture from the camera, the camera needs to know the lens's available aperture values, and this feature is only available on lenses from the A series and later. This is why, in the thread where you were looking for recommendations, I tried describing the different lens series and asked which one you wanted to use with the tubes. You answered K so I suggested the AT-22 tubes. What lens are you putting on the tubes?

09-10-2012, 11:15 AM   #17
Senior Member

Join Date: Jan 2009
Location: Blacksburg, VA
Photos: Albums
Posts: 284
Original Poster
I'm using it was a Tamron SP 90mm 1:2.5 macro with a PK/A adaptor... I don't know much more about it than that... It's definitely manual focus, but without the extensions tubes I can control the aperture in camera. The PK/A adaptor has 3 contacts...

Sorry, I'm learning and appreciate all of the input, knowledge and advice!!
09-10-2012, 12:14 PM   #18
Loyal Site Supporter
baro-nite's Avatar

Join Date: Aug 2011
Location: North Carolina, USA
Photos: Gallery | Albums
Posts: 4,364
Don't worry; I'm not nit-picking. I guess you can't return the tubes to KEH now that you've sanded off the anodized finish (I didn't realize these tubes came with that), but I should think you could sell them here if you don't want to keep them. KA extension tubes are hard to find. What I and others have done is to convert KA (or KAR, a Ricoh variation on KA) teleconverters to extension tubes by removing the optics. With certain 2x TCs this is easy to do, but you have to get the right kind because with many TCs the optics can't be easily removed. The ones that I have are about 25mm long, so not as versatile as a proper set of tubes, but fine for extending a macro lens as in that case you probably want a relatively large amount of extension anyway.
09-10-2012, 08:44 PM   #19
Inactive Account

Join Date: Dec 2008
Location: North Carolina
Photos: Albums
Posts: 1,720
QuoteOriginally posted by baro-nite Quote
With certain 2x TCs this is easy to do, but you have to get the right kind because with many TCs the optics can't be easily removed.
Usually the cheaper the easier, since they have less elements.

02-22-2013, 03:17 PM   #20
New Member

Join Date: Nov 2010
Photos: Albums
Posts: 5
Anodized or black extension tubes K5 problem solved by this thread

I was having problems with my K-5 and the Green button when using some anodized or painted black extensions tubes. The camera was not stopping down the lens when using the Green Button, even though I had enabled the use of the aperture in the custom menu. I found that this thread said you needed to remove the black anodizing on extension tubes for the camera to use the Green button. Thank you for finding me the solution. You think this would be in the camera manual someplace, that the camera has to have bare metal against the contacts for the Green button to work in Tv Shift mode when using manual lenses, especially when considering Pentax is a leader in the use of legacy lenses. At least now my problem has been solved. Thanks again.

  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
extension, k-mount, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
Extension Tubes rickbehl Pentax Medium Format 9 11-23-2016 01:02 AM
PK/A extension tubes? wowtip Pentax Camera and Field Accessories 110 09-15-2012 05:18 AM
I'm looking for Extension tubes for the k5 LightSpeed Pentax K-5 16 01-01-2012 06:24 PM
K-5 and Extension Tubes canoetripper Pentax K-5 11 10-26-2011 08:27 AM
? about extension tubes janstew Troubleshooting and Beginner Help 7 06-01-2011 02:07 PM

All times are GMT -7. The time now is 06:17 AM. | See also:, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]