Hi

I am aware that Canon currently sell EF series extension tubes that maintain the full electronic coupling between the camera body and EF series lenses, even though they still recommend manual focussing.

My question is, however, what happens if you use older (or non-Canon brand) extension tubes without the electronic coupling with EF series lenses? Manual focussing could still be achieved but how would you set the aperture (as far as I know this can only be done through the camera body)? Do the EF lenses default to a particular aperture setting in the absence of electronic input from the body?

Thanks for any info you can provide on this.

-- Graham Evans (Graham.Evans@dotars.gov.au), May 12, 2002

Answers

Did you find any EF mount extension tubes without electronic coupling? As far as I know there is no such extension tubes.

Kenko's extension tubes for EF mount (I'm not sure it's marketed in your country) have electronic coupling and work well.

Without electronic signal from camera body EF lens aperture does not work and keep at wide open.

Ken

-- Ken Itoh (KEN@clara.oc-to.net), May 12, 2002.

I agree with Ken re: the tubes - I've never seen any which lack some form of electronic coupling. You can't use Canon FD (manual focus) tubes with EF lenses and EOS bodies because a) the lens mount is of a different diameter and b) EF mounts are bayonet and FD mounts are breech-lock.

I'm not sure about the lenses staying wide open, however. All the EF lenses I've tried (just half a dozen, mind you - there may well be differences in other lenses) stay at whatever aperture they're set to when power to the body is disconnected. So you can set a lens to, say, f/8, remove the camera battery and the lens seems to stay there.

-- NK Guy (tela@tela.bc.ca), May 13, 2002.