3rd Party extension tubes problem, Canon.

[dizidav]

I have a set of 3rd party extension tubes, usual Ebay AF ones, they work perfectly on my 40D, but wont work on my 5D, anybody got any idea why this should be.

 

[Brachytron]

What exactly doesn't work? Do you get under exposure? I had a similar problem with my Sigma macro lens on my 7D2. Apparently Canon deliberately make changes to firmware that cause third party products problems. In the end, Sigma wrote a firmware update to correct the problem, but I guess that isn't possible with your tubes.

 

[dizidav]

Wish it was that easy, everyting works as it should on the 40D, when I try them on the 5D Iget no AF or Aperture control, comes up with 00 in the aperture window, no error messages, shutter will fire, but stuck with minimum aperture, dosnt matter what lens I use.
Very strange, I always thought the contacts were the same on all EOS bodies.

 

[Canon Bob]

It would appear that one or more of the pass through contacts isn't connecting.....either the power or data (or both....less likely). The pins that you see in the camera body are spring loaded to allow for tolerances in manufacture (both on the body and lenses). It may well be that the pins on the 40D are marginally more forward than the 5D and this is enough to allow the tube (with its possible out of tolerance contact plate) to make contact.

If you take a shot at maximum aperture on the 5D (your only option with this fault) and check the EXIF to get some clues. If the lens has been correctly identified then the data contacts are good and it points to the lens power contacts being the problem. If the lens isn't identified then it's fair to assume that it's the data pins that are not connecting as lens power isn't required at this stage.

Bob

 

[dizidav]

Thanks for the info Bob, the exif dosnt record the lens, so its the data pins, not much I can do with that, so manual lenses only.