Canon Extension Tube EF25II

I just recevied the Canon Extension Tube EF25II and the instructions advise to use manual focusing instead of auto. It was my understanding that auto focus was usable. My primary lenses for the extension tube are the 400mm f/5.6 and 100mm macro.

Any comments or experiences are appreciated.

I used mine with the 400L on auto focus without a problem.

Thanks rathke. I'm at work now and will try it out tonight.

Both the EF12II and the EF25II work fine in full auto. They maintain communications with the lens. That said, when you get into macro work, there are going to be many times that manual focus is more accurate and the focus will not be continually hunting like it is prone to in auto.