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10-27-2013, 01:04 AM   #1
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Pentax and Vivitar auto extension tubes

Hi there, I just bought two sets on auto extension tubes. one is pentax k auto extension and other one is vivitar at-22 auto extension.
I am using smc-m 50mm f/1.4 on them. what i want to ask is both work great im M mode using green button for stop down metering. but in aperture priority mode, when i use pentax tubes, they set the aperture wide open i-e at 1.4. and changing ther aperture ring on lens doesn't do anything but when i use vivitars even in aperture priority mode, they meter properly and changing aperture ring to lower apertures effictively work.. i-e the camera meters properly... i just want to know y is that......y pentax doesnt?
Hope u get what i am asking..
kindly reply

10-27-2013, 01:41 AM   #2
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The Pentax tubes are working as expected, Av mode will not work properly without A contacts on a K mount and the aperture stays wide open no matter what the ring is set to.

Do you see the viewfinder getting darker with the Vivitar tubes as you close the aperture with the ring? If so there is something wrong with them, they have the aperture coupling and are supposed to hold the aperture of the lens open until the shot is taken. Essentially they are making the lens act like an M42 lens instead of a K mount.
10-27-2013, 04:30 AM   #3
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QuoteOriginally posted by elliott Quote
The Pentax tubes are working as expected, Av mode will not work properly without A contacts on a K mount and the aperture stays wide open no matter what the ring is set to.

Do you see the viewfinder getting darker with the Vivitar tubes as you close the aperture with the ring? If so there is something wrong with them, they have the aperture coupling and are supposed to hold the aperture of the lens open until the shot is taken. Essentially they are making the lens act like an M42 lens instead of a K mount.
I am using them on Pentax K-01. With vivitar in live view when I increase f stop from f/1.4 to f16, the screen gets darker both M or Av modes, it does change shutter speed in av mode
10-27-2013, 04:42 AM   #4
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Then there is something wrong with the aperture coupling of the Vivitar tubes. The screen should not be getting darker when you turn the aperture ring, the aperture should only close when the shot is taken.

10-27-2013, 05:38 AM   #5
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Unless you have the version with contacts you probably need to scrape off some of the black coating on mount so that the electrical contacts on the body are shorted. I think only pin 7 the "data" pin need be shorted. You can test this by using a small bit of metal foil over the contacts. Also note that tubes should be mounted on to the body and then the lens as per Vivitar's instructions.

See this thread
https://www.pentaxforums.com/forums/pentax-camera-field-accessories/233995-ow...ion-tubes.html

Link to manual in above thread.

Last edited by Not a Number; 10-27-2013 at 05:43 AM.
10-28-2013, 10:08 AM   #6
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QuoteOriginally posted by Not a Number Quote
Unless you have the version with contacts you probably need to scrape off some of the black coating on mount so that the electrical contacts on the body are shorted. I think only pin 7 the "data" pin need be shorted. You can test this by using a small bit of metal foil over the contacts. Also note that tubes should be mounted on to the body and then the lens as per Vivitar's instructions.

See this thread
Owners: Vivitar AT-22 macro extension tubes - PentaxForums.com

Link to manual in above thread.
Pardon me. But kindly clarify. Where do I have to scrape off paint on extension tube. The base that contacts with lens or the one which contacts body.
Secondly what benefit will I get after making contact with data pin.
Will it give aperture reading or what.
Thanks
10-28-2013, 02:02 PM   #7
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Simple depending on which body you have the camera will not actuate the stop down lever unless a lens is attached. The only way the camera body knows if a lens is attached is if it gets an electrical signal through the pins on the mount. If the lens/tube mount is non-conducting the lever will not actuate. Newer DSLRs like K7, K5, K30, all behave in this manner. Older cameras like the K-10D and K-20D do not need this modification but sometimes you need to do it in order to get catch-in-focus.

See this thread:
https://www.pentaxforums.com/forums/120-general-technical-troubleshooting/132...ion-tubes.html
10-28-2013, 02:24 PM   #8
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If the paint is the problem the aperture won't close, that is not currently your problem, but it would be your problem if the aperture coupling in your tubes was actually working.

10-28-2013, 02:46 PM   #9
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Oops, my bad. That's what I get for reading messages after prolonged periods without sleep. I read it as the problem was with the Vivitar.

Check the levers on the Pentax tube. Do the move freely? Are they bent? Have they been clipped off? If someone tried using these on a Canon body they sometimes cut off the levers so as not to hit the mirror.
10-29-2013, 01:35 AM   #10
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I am confused more than before..
On manual lens, vivitar is doing fine. i-e in m mode when i press green button, it takes exposure properly and also it shows metering bar and in av mode its metering properly and i can change aperture on the lens.
while pentax tubes work in m mode i-e in m mode pressing green button takes exposure properly but it does not show metering bar. but in av mode, its not changing aperture i-e its stuck to f1.4 whether i turn aperture ring to f8 or f16, it is taking exposure for f/1.4 and changing shutter speed accordingly.

now what i want to ask is, if thats the way these tubes should behave. I have not scraped off any paint yet from vivitar.
and what benefit will i get if i scrape off paint.
plus is there any way if these tubes can work with da lenses, if they don't, its fine coz i want to use them on manual lenses...so scrapping off paint will give me what other benefit in case of vivitar....
plz ignore my ignorance....
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10-29-2013, 03:08 AM   #11
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Mount the lens on the camera with no tubes, that is exactly how it is supposed to work, just as you describe the Pentax tubes.

If you prefer the way the Vivitar tubes work now, don't mess with them. Scraping the paint off will not change how they work because the problem is in the aperture coupling. There is a misalignment somewhere and they are not allowing the camera to keep the aperture of the lens wide open for focusing and composing.
10-29-2013, 10:23 AM   #12
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QuoteOriginally posted by elliott Quote
Mount the lens on the camera with no tubes, that is exactly how it is supposed to work, just as you describe the Pentax tubes.

If you prefer the way the Vivitar tubes work now, don't mess with them. Scraping the paint off will not change how they work because the problem is in the aperture coupling. There is a misalignment somewhere and they are not allowing the camera to keep the aperture of the lens wide open for focusing and composing.
Ok. Thanks a lot guys. I think Iam happy with what they r. Not messing with them would ne wise.
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