Extender question

Just bought my wife a 2X extender for her Canon 100-400 L. She's using it on a 20D. Says there's no AF with the extender. I've searched the forums and there seems to be confusing input on this issue. Is there, or is there not, AF with this extender on a 100-400? Documentation indicates AF is slower, but how much slower? Canon web site also indicates there is AF ....
any input from users with the same equipment would be appreciated.
cheers,
jim

A 20D is incapable of AF with a 100-400L and a 2x Extender.

A 20D can only AF with lenses which have a maximum aperture of f/5.6 or larger. Since the 2x Extender cost you two stops, the 100-400L effectively has a maximum aperture of f/11 at the long end. Way out of spec..

Cadwell:
Thanks for the quick reply ... looks like she'll be using that setup with a tripod ....
cheers,
jim

Jim,

Please take a look at the -=READ FIRST=- EOS "Sticky" Thread at the top of this foprum,..

In one of the links, I think you may find some additional info on teleconverters that you may find helpfull.

As an aside, the 20D (also 10D, D30, D60, Drebel) will also not achieve AF on the 100-400 with the 1.4xTC.

CDS:
apologies for asking a question for which there is already a suitable explanation ....

JIM:
thanks for the added info

cheers,
jim

If this is of any help:

http://www.fredmiranda​.com/TipsPage/

The above mentioned "tape trick" may be worth a try in some cases.. but is unlikely to work with a 2X + 100-400mm on a 20D.. this is just too far out of spec. Many have good results with the 1.4X on the 100-400mm,....

HOWEVER.. this trick is NOT without it's risks!

On the bright side.. it may be worth a try in many acases.. and things may work fine.

Worst case scenario results in a burned out focus motor.
If you note ANY signs of unusual behavior (hunting, noise, sporadic AF performance) I'd advise removing the tape ASAP.

Thanks all the same, but ... there's too much of an investment already in the camera, lens and extender (remember, we're talking Canadian dollars here) to risk any damage using the "tape trick."

cheers, and thanks all,
jim

Go out and buy her the 1.4x extender. It works with the 100-400 lense. The 2x extender works with the 70-200 mm f2.8 lense.

Phil Hall

Somebody might ask the question about risks of the tape trick.

First of all, you could apply the tape to the teleconverter's gold contacts, or you could apply it to the camera's gold contacts. Since the camera is more valuable than the teleconverter, you risk more by doing it to the camera.

Second, you use tape to serve as an electrical insulator between the gold contacts. Well, most tape has one slick side and one sticky side. The sticky side will make it stick to the gold contacts, and if you want to do this semi-permanently, then OK. However, if you intend to remove the tape, the stickiness may be left on the gold contacts. Worse yet, once the stickiness is left on the gold contacts of the teleconverter, you may transfer it to the gold contacts of the camera. That stickiness may act as an intermittent insulator even with only your favorite lens in place. Not good.

So, if you feel compelled to use the tape trick, use two pieces. (Imagine this) Use one piece an inch long, and then use another piece 3/4 inch long, and place the shorter piece sticky side to sticky side with the longer piece so that there are only two 1/8 inch sticky ends to hold the tape in place _away_ from the gold contacts. This still is not foolproof, but it can eliminate some potential problems.

---Bob Gross---

The 20D won't autofocus with the 100-400L and 1.4x Extender either, sorry. That combination only works on a 1 Series dSLR.