I am trying to deside which lens to get the 100-400 L or the 300 f4L. my question is will my auto focus work using a tamron 1.4 pro T/C on the 100-400 4.5 5.6 L. Canon tec.suport told Me that it would with my elan IIe body although on the specs for the 1.4 T/C said otherwise.One other thing the T/C worked with my 100-300 4.5-5.6 lens. So what do you think? Personal experience would be best.While I'm at this has eny one ever had problems with the auto focus with the 70-200 F4.L locking on to the subject.

-- Brian Reynolds (cwesbroo@indiana.edu), January 17, 2002

Answers

It shouldn't work but it might! The IIe is only designed to AF at f5.6, not f8 (the 3 and 1v AF at f8). However I assume the Tamron TCs still don't report the correct aperture to the camera body so it will attempt AF. The result is you may get AF but it probably won't be very good.

The 3004L will AF properly (accurate and positive AF lock), especially when used with the CAnon 1.4x TC. With third party TCs it will probably do OK too.

-- Bob Atkins (bobatkins@hotmail.com), January 17, 2002.

Brian:

My 100-400 L will not AF with the Tamron 1.4X Pro (white one) on an EOS 5 (A2e), the combination does work with a 1v however. Excluding the protruding element, I think the Tamron is set up to work just like the Canon OEM extender.

-- Gary Russell (gr_russell@earthlink.net), January 18, 2002.

You'll probably have to try it. I have an older Tamron 2x extender that does not send the aperture data, and consequently will "attempt" to autofocus at equivalent f11. Really it just ends up hunting unless you happen to be focusing on a straight black-and-white high contrast edge (which is about how often?). Tamron may have updated their contacts in the new pro series to feed the real aperture, but I haven't tried one.

-- Les Gyug (les_gyug@telus.net), January 18, 2002.

I had the camera shop to get one in for me to try.it did not work.I was hoping that it would with ideal lighting.I think that my best bet will be the 300F4 I really don't want to get a prime lens but without a good alternative that is about it. Maybe we should all gang up on canon to add a usm to the 100-300 L lens at a resonable cost.I would be happy with that.(FAT CHANCE) at least I know that my images will be better this sping. I use the long lens to photograph Bald Egales atlake monroe during the nesting seson.well,anyway thanks everyone for your imput it was helpfull And maybe someone else will also benafit from this.

-- Brian Reynolds (cwesbroo@indiana.edu), January 19, 2002.

Why don't you just buy the 100-400? At the long end, it is almost as long as the 300+TC. Then, if you later upgrade to an EOS 3 or 1V, or similar, you can get the Canon 1.4X TC and it will AF properly with the centre point.

I have the 300 F4L IS, which is very nice indeed, and works very well with the 1.4X TC, but it seems you want a zoom.

I have never had any probs with the AF on my 70-200 F4L. If anything, it's always been the best of my lenses in this respect (alongside 24-85USM and 300 F4L IS USM), and works well with the 1.4X TC also. I suspect the body has rather more bearing on this though.

-- Isaac Sibson (isibson@hotmail.com), January 20, 2002.

The Tamron Pro 1.4x does not autofocus with the 100-400 IS zoom. With lenses that have the extra three connections in them (L telephotos only? I'm not sure), the Tamron Pro TCs send the proper effective f/stop to the camera body. Thus, when you view through the lens + TC combo, you will see the correct effective f/stop. With an Elan IIE which cannot AF at f/8, the camera body shuts off AF. This is first hand experience.

Interestingly, with lenses w/o the extra three connectors, such as my 85mm/1.8, the TC does NOT send the camera the correct f/stop info. When I connect this combo, the camera shows an effective aperture of f/1.8 instead of f/2.5. The lack of the three extra connectors (leads, or whatever they are called) is the only difference I can attribute this behavior to.

-- aricat91 (lmhample@mindspring.com), January 24, 2002.