Cannon Extender EF 2x11

[Primo-Photo]

I purchase the Canon Extender EF2x11 and the auto focus does not work on my EF100-400 F4.5 -5.6 L IS USM. I have a canon 20D. Has anyone had this problem?

[Jamoke]

I have the Tamron version (a little cheaper) and it had a similar problem. First time I connected it to my 20D the contacts were a little dirty (Fresh from the box)... I wiped the contacts clean, and it worked like a charm.

Check the Contacts, on both the camera, both sides of the extender, and the lens that your connecting to. - Let us know if it's still a problem.

[DanielB]

I purchase the Canon Extender EF2x11 and the auto focus does not work on my EF100-400 F4.5 -5.6 L IS USM. I have a canon 20D. Has anyone had this problem?

yep, tape the contacts.:thumb

[Primo-Photo]

Sorry, but what do you mean by tape the contacts.

I have two some lens. The 70-200 F/2.8 L USM and the 100 to 400 F4.5-5.6L IS USM. The auto focus works on the 70-200, but does not work on the 110 to 400.

Is the a proper way to clean the contacts?:dunno

[Bob Bell]

Sorry, but what do you mean by tape the contacts.

I have two some lens. The 70-200 F/2.8 L USM and the 100 to 400 F4.5-5.6L IS USM. The auto focus works on the 70-200, but does not work on the 110 to 400.

Is the a proper way to clean the contacts?:dunno

Consumer bodies will only auto focus is the max aperture is 5.6 or faster. This mean you cannot use any TC on the 100-400 made by canon. On Pro bodies you can Auto Focus with the center point to F8. If you need to use Teleconverters, Tamron makes a cheap line. The aperture will be unaffected with the tamrons and the bodies meter adjusts to make up the stop in light loss.

Hope that helps.

[DanielB]

Sorry, but what do you mean by tape the contacts.

I have two some lens. The 70-200 F/2.8 L USM and the 100 to 400 F4.5-5.6L IS USM. The auto focus works on the 70-200, but does not work on the 110 to 400.


thats becasue the 70-200 2.8 is a 140-400 5.6 with the 2x converter, and the 100-400 4.5-5.6 is a 200-800 9-11 with the 2X all you need to do is tape the 3 contacts that report apeture to the camera and you'll be just fine. but the 20D doesn't autofocus past f/8. and like Bob said, the pro series do, but you need center autofocus point... i think there was a thread about taping the contacts here not too long ago:scratch

the reason Jamoke's extender worked was becasue the Tamron extender is missing the end 3 contacts that report apeture. :thumb

[gluwater]

thats becasue the 70-200 2.8 is a 140-400 5.6 with the 2x converter, and the 100-400 4.5-5.6 is a 200-800 9-11 with the 2X all you need to do is tape the 3 contacts that report apeture to the camera and you'll be just fine. but the 20D doesn't autofocus past f/8. and like Bob said, the pro series do, but you need center autofocus point... i think there was a thread about taping the contacts here not too long ago:scratch

the reason Jamoke's extender worked was becasue the Tamron extender is missing the end 3 contacts that report apeture. :thumb
Exactly what DanielB said. At f/9-11 you will need very bright light to use the AutoFocus with the taped contacts. Basically by taping the contacts the 20D does not know there is a TC on the lens so it still thinks it can AF. The thing you need to keep in mind is that you are still losing light so the AF may work but it may be slow and hunt a lot. Check here for a little info on taping the contacts.

[DanielB]

Check here for a little info on taping the contacts.

AH ha, i looked and looked for that thread but couldn't find it. thanks:thumb

[Jamoke]

Great Link - I hadn't realized I was missing the contacts. Well, I guess I'm not missing them, I just don't have them. But thanks for the link and the info.