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11-18-2014, 06:33 PM   #1
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How to use extension tubes

Hi. Can someone explain whats going on and how to use it?
- I have k50 camera. I just bought Asahi extension tube (3 pieces) for Pentax (K mount).
- I have snapped it all together -- camera, extension tube, followed by my autofocus lens -- everything fits, but seems to be dead. My electronics are flashing "F--" and the lens is not operable, the camera thinks I am in Manual Focus mode.
- I am able to control the amount of light entering the camera by rotating the f stop ring on my lens, but thats it -- nothing works in auto mode
- I have tried flipping a AF/MF switch on the body of the camera and go into a manual mode, but it didnt help -- if the electronics are messed up, I cannot press the button and take a picture.

So what is the right way of using this thing? How do I take a picture? How is it supposed to work? Even if it did work, if everything is manual, what is the difference between this expensive high quality tube and a cheap piece of plastic tube? Is there anything "auto" about this at all?

Thank you (please take it easy on the technical jargon when getting back to me -- I just need to know what button to press....)

11-18-2014, 06:36 PM   #2
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You need to change a setting in your camera to allow use of the Aperture Ring. On the K-50, I'm not entirely sure where that is, but it's in the C (custom) menu. Also have a read here:

https://www.pentaxforums.com/forums/58-troubleshooting-beginner-help/110658-u...x-dslrs-f.html
11-18-2014, 06:48 PM   #3
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If they are the regular Ashai K tubes, it will trigger the aperture close down when you have aperture ring enabled as in photolady's instructions, but it won't communicate the aperture to the body or autofocus, since the tubes have no electronic contacts on them. You will be using it in M mode, with green button stop-down for metering. A mode will not work, since digital-era Pentax bodies communicate aperture information electronically only and not via the mechanical aperture linkage.

Last edited by dcshooter; 11-19-2014 at 06:56 AM.
11-18-2014, 06:51 PM   #4
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Those extension tubes have no electrical contacts so any lens used on them will only work in manual mode. To use your camera in manual mode see the following:

https://www.pentaxforums.com/forums/54-pentax-lens-articles/110657-how-use-me...k-x-k-7-a.html
https://www.pentaxforums.com/forums/53-pentax-dslr-camera-articles/100260-man...ic-lenses.html

The basic settings in your menu options are: enable use of aperture ring, green button in TAv or M mode to Tv shift and DOF preview to Optical.

With extension tubes you have to get close to the subject and focus by moving the camera and lens (or object). The lens should normally be set to infinity. Set the f-stop you want on the aperture ring and press the green button - this should measure the light through the lens and set the appropriate shutter speed. Take you exposure. Depending on the focal length of the lens and amount of extension the focusing distance between the lens and the object can be a few inches to as little as 1/4 of an inch.

11-18-2014, 07:28 PM   #5
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QuoteOriginally posted by Not a Number Quote
With extension tubes you have to get close to the subject and focus by moving the camera and lens (or object).
This is true for bellows as well and is even the best way to work with a dedicated macro lens. Special macro "focus rails" are used to make this easier. Do a Google search for "macro focus rail" for more information.


Steve
11-18-2014, 07:48 PM   #6
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QuoteOriginally posted by stevebrot Quote
This is true for bellows as well and is even the best way to work with a dedicated macro lens.
When using bellows you can focus by changing the extension but you change the magnification at the same time. This may not be the desired effect.
11-18-2014, 10:28 PM   #7
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just go fully manual, ie. lens with aperture ring etc. it makes life easier
11-19-2014, 04:57 AM   #8
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Thank you so much, guys. I have just watched the youtube video explaining all that -- havent tried it, but sounds right. Thanks again!!!!

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