No autofocus with Extension tubes?

cwphotos

I have a canon 25mm extension tube and I cant get my autofocus to work. Im just assuming I have to do manual for all this. Can someone confirm?

troglodite

I found this on wikipedia - I went there because I've never used one and I've forgotten what they were used for. Maybe this helps.

Extension tubes without electrical contacts will not allow the camera to control the lens disabling autofocus and forcing a user to shoot wide open. More expensive extension tubes contain electrical contacts allowing the user to use autofocus and control the aperture of the attached lens.

cwphotos

yeah mine has the contacts it just sits there and backfocuses a ton of times and nothing happens.

troglodite

Then I think it is the lack of light. Since there is less light now hitting the sensor -

I have that problem with my cheapo 100-400mm and a teleconverter (tried some moon shots) Also if I just the teleconverter on my smaller lenses, sometimes they focus sometimes they don't.

I would test it on a bright day at a big ap and see if it will focus correctly.