I've searched the archives but have not come up with anything that will answer my question. A friend recently gave me a set of Canon extension tubes(says M set on box-5mm,10mm and 2 20mm.) When I connect any of them to my FTBn I lose the ability to meter and the diaphram stays wide open. Anyone have any experience on how to properly use these. Thanks.

-- Bill Griffin (billgriffin@sympatico.ca), December 10, 1999

Answers

Sometimes with extension tubes, the order of connection matters, so that the lever closing the diaphragm connects properly. If you have been attaching the extender to the body first, try attaching it to the lens first, or vice versa.

I try to remember to stop down manually to check everything works on my extension tubes, as I can never remember which way is right, just that it is important.

Good luck.

-- Roger Broadbent (roger_broadbent@yahoo.co.uk), December 13, 1999.

The M series tubes are manual only, and stopped down metering. They do not couple.

If you activate the stopped down metering control, the aperture should close and you meter that way.

-- Terry Carraway (TCarraway@compuserve.com), December 13, 1999.

Bill,

Canon extension tube set "M" is completely manual and transmits no information or action between camera and lens. It is just a simple extension of the lens mount for close focusing. To use them you must set the lens for manual operation. For Canon breech lock lenses do one of the following. With the lens off the camera, find the aperture stop down lever. It is the chrome plated lever at the 6 o'clock position as you look at the rear of the lens. Push the lever to the right, to the limit of it's travel. With most Canon FD lenses you'll feel it click into a detent and stay in place. Some 50mm f 1.8 and 35mm f 3.5 lenses may be different. On these you'll see a black switch to the immediate right of the stop down lever, I think it's marked with a red "L". Again, push the stop down lever to the right and while holding it in position move the lock switch. The lever will stay in position. The lens is now set for manual operation. Mount the lens on the extension tubes. Now, when you turn the aperture ring on the lens, the iris will close or open. To meter for exposure, adjust the aperture ring so the meter needle, not the follower ring, aligns with the small rectangle near the bottom of the right hand side of the viewfinder. The viewfinder will darken as you close down the aperture. This is normal for "stopped down metering". When you remove the extension tubes for normal distance photography make sure you reset the aperture lever on the back of the lens for automatic operation. Note that the above procedures for manual aperture operation may not work with non-Canon lenses and won't work with later Canon "New FD" bayonet mount lenses.If you need further clarification, check your FTb instruction book or E-Mail me directly.

Bill

-- Bill Salati (wsalati@powwowmail.com), December 13, 1999.

As mentioned the New FD lenses won't work with the 'M' extension tubes, but there is a fudge. As you slowly mount the lens on the tubes, watch from the front and when you get half way you'll see the diaphragm close down. In this way you get stopped-down metering. Don't go any further or it'll open again. It's not perfect but it works for me.

-- Steve Phillipps (steve@redvixen.freeserve.co.uk), January 09, 2002.