I have bought a set of extension tubes to use with my EOS3 and telephoto lenses. The instructions say quite specifically that a) you can't use 2 extension tubes together and b) you should only use MF. From practical experience is this correct - my recollection from looking at Artie Morris' book was that he regularly uses extension tubes combined.

TIA

Andrew

-- Andrew Hardacre (andrew@jhardacre.freeserve.co.uk), September 13, 2001

Answers

Andrew,

You can purchase "auto" extension tubes, which have all the electrical contacts necessary for your EOS to communicate with the EF lenses. You should still be able to autofocus & aperture with no problems. When adding tubes to a lens, you will lose infinity focus (distance focus), but since you are working at macro distances that should not matter. Your instructor may be recommending shooting with manual focus so that you can control what is in focus better. Depth of field is very shallow in macro work & the camera may not know what you are truly aiming at. The use of a viewfinder magnifier will help immensely in this. Canon makes one, and I'm sure there are third pary makers as well.

In response to stacking tubes: It should be no problem at all. In fact, Kenko (and likely others) sell sets of tubes, and suggest stacking in different combinations to achieve different close focus magnifications.

Here's some links for you:

Phot ography Review

Tokina/Hoya/Kenko products web site

I hope I've answered your questions. Enjoy your shooting!

-- Hung James Wasson (HJWasson@aol.com), September 13, 2001.

Oops...my brain translated "instructions" to "instructor" -- sorry if I caused confusion! :-)

The Canon EOS-3 manual says to not stack multiple tubes & use only in manual focus? That's interesting! As long as the lens/tube/body assembly is properly supported, I don't see any problems.

-- Hung James Wasson (HJWasson@aol.com), September 13, 2001.

Hmm, I've never seen the item in the -3 manual about not stacking tubes - maybe that explains why I do it and it works without a problem, at least with my Kenko tubes.

It might be that the Canon 12mm and 25mm have additional electronics in them that may cause problems. This is just speculation on my part and maybe someone who has disassembled a Canon tube could elaborate on that.

Back to the original query, just try it and you should have no problems.

Dick

-- Richard Tope (RTope@yahoo.com), September 13, 2001.

Thanks for the reassurance - the instructions I refer to are in the pamphlet that comes with the extension tubes not with the EOS3 manual - I briefly tried the extenders last night stacked round a 1.4x converter on the 300mm USM IS lens - it would not autofocus but with manual focus there seemed to be no problem. (The AF does hunt but does not find focus).

Tomorrow, Saturday, I'll have a more lengthy try.

regards

Andrew

-- Andrew Hardacre (andrew@jhardacre.freeserve.co.uk), September 14, 2001.

Andrew,

Out of curiousity, what brand are those tubes? My understanding is that the Kenko's work great (I don't yet own a set, but they are the most recommended ones I heard about).

-- Hung James Wasson (HJWasson@aol.com), September 14, 2001.

The tubes are Canon's own. They are far from cheap. In Britain I paid £150 for a 12mm and 25mm set. I did not look at the Kenko ones on the basis that I thought it better to match the tubes to the body + lens if possible.

-- Andrew Hardacre (andrew@jhardacre.freeserve.co.uk), September 15, 2001.