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05-05-2015, 11:21 PM   #1
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645 A Extension Tubes

Looking for a little bit of help from anyone that has used , or uses the auto-extension tubes. Today I received a set of the 1,2, and 3 tubes. So my question is about Ext. Tube #1.

If you are looking at the rear of the tube with the orange alignment dot in the 12' o clock position their are two articulating levers one in the 3' o clock position( right side), and one at the 6' o clock position( bottom). The bottom lever appears to control the aperture when linked to the camera and is spring tensioned. The lever on the right moves freely without any spring tension. Should this be the case with the lever on the right? I ask because I noticed that Ext. tube 2 and 3 both levers are spring tensioned.

I noticed that on the front of the tube # 1 the levers are physically different than they Ext. Tube 2 & 3. Maybe this accounts for the difference?

I did try the # 1 tube on the camera, and the aperture does seem to be functioning properly. Just concerned that if this is not how the freely moving lever is supposed to function that I could possibly damage something. Also, that I should return the tube set , and look for another.

Thanks for any help....

05-06-2015, 12:23 AM   #2
Jonathan Mac's Avatar

Join Date: Apr 2009
Location: Madrid, Spain
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I bought a set of 645 extension tubes last year and found exactly the same thing. I assumed that tube #1 was broken, but it works perfectly. Now if there are other examples it means that either that's normal or there is a weak point in the design or manufacture that results in a broken spring.

Maybe because tube #1 is smaller than the others there wasn't space to fit the spring mechanism into it?
05-06-2015, 04:12 PM   #3
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Thanks for taking your time to respond Jonathan. That is good to hear. I think your right about the size making a difference; maybe less torque is needed because of the size of the tube hence only having one spring?

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