10d + Canon 100-400 IS + Canon 1.4 Extender = No focus :-(

[gthorn]

Hi

I asked this question before for my D30 + 1.4 extender II + 100-400mm lens and someone told me that this combination doesn't autofocus, but that the same lens combo with a 10d would focus. Well, it doesn't. It doesn't even try to focus and the indicator doesn't flash to say it couldn't focus either. It's like the lens has been set to manual focus.

Can anyone tell whether this combination is supposed to autofocus ?

All answers appreciated.

Graham :(

[Patrick 10D]

Check this link:

http://www.bhphotovideo.com/FrameWork/charts/canon1_4xExtender.html

For your lens and camera, it says:

AF is ONLY possible with the EOS-1v and EOS-3 cameras, ONLY when using the center focusing point.

[Cadwell]

Hi

I asked this question before for my D30 + 1.4 extender II + 100-400mm lens and someone told me that this combination doesn't autofocus, but that the same lens combo with a 10d would focus. Well, it doesn't. It doesn't even try to focus and the indicator doesn't flash to say it couldn't focus either. It's like the lens has been set to manual focus.

Can anyone tell whether this combination is supposed to autofocus ?

All answers appreciated.

Graham :(

Sorry Graham - not good news, whoever told you that the 1.4x extender + 100-400IS would autofocus on a 10D was wrong.

A 10D can only autofocus with lenses with an effective maximum aperture of f/5.6 or larger. The 100-400 IS's maximum aperture of f/4.5 + one stop for the extender takes it out of that range.

You could always try the tape trick if you are feeling adventurous... some people have had success with that.

[Miika]

from Canon "Canoneone" -magazine 2004:

Considering extenders EF 1.4x II and EF 2x II

(corrected numbers with boldface)
EF 1.4x (effective aperture becomes smaller by 1 stop; eg. F4.5 to F6.3)
EF 2x (effective aperture becomes smaller by 2 stops; eg. F4.5 to F9)

Only manual focus is possible if largest effective aperture is smaller than F5.6.

(EOS-1Ds, EOS-1D Mark II cameras: smaller than F8)

**EDIT: removed a nonsense suggestion

Miika

[Cadwell]

from Canon "Canoneone" -magazine 2004:

Considering extenders EF 1.4x II and EF 2x II

EF 1.4x (effective aperture becomes smaller by 1 stop; eg. F4.5 to F5.6)
Miika

Sorry Miika, but 1 full stop wider from F/5.6 is F/4 not F/4.5.... so the maximum aperture of the 100-400 + 1.4x TC is smaller than F/5.6 - that's why it doesn't work.

[Miika]

Thanks Cadwell for correcting me! I should have found the table next page...

Combination 100-400 mm F4.5-5.6 L IS USM + 1.4 extender: F6.7-54

It's clear that autofocus will not work on 10D.

Miika

[CyberDyneSystems]

You could allways try the tape trick :)

[gthorn]

Thanks very much, I should have done more research on this before posting my question. My eyesight is just not good enough for manual focusing quickly (I take pictures of birds, wildlife and dolphins riding waves which are impossible without autofocus) so I need to investigate the tape trick if I can find it.

[Cadwell]

Thanks very much, I should have done more research on this before posting my question. My eyesight is just not good enough for manual focusing quickly (I take pictures of birds, wildlife and dolphins riding waves which are impossible without autofocus) so I need to investigate the tape trick if I can find it.

Sorry, I've heard of the "tape trick" - you tape over two or three pins on the lens (teleconvertor?) and that stops the camera recognising the decrease in aperture, but I don't know the details of which pins. I know some people here use it with reasonable results and I am sure one of them can let you know how it's done.

[chris maddock]

http://photography-on-the.net/forum/showthread.php?t=23667&highlight=tape

from a forum search on "tape" ;-)

KRs
Chris

[Cadwell]

Mmmm... I just tried it with my 70-200 f/4L and EF Extender II 2x. It didn't even come close to focusing... even in good light.

[gthorn]

I found the "tape" information and tried it. It seems to work quite well in good light. The lens focuses readily in good light and I still have the option of switching to manual focus when the subject allows.

[drisley]

On that link it says that

"If the EF 70-200mm f/2.8L USM lens is attached to an EOS camera having multiple focusing points and an Extender is attached to the lens, only the center focusing point will be usable for AF."

However, for the F4L and the F2.8 IS versions, there is no limitation like this. Doesnt that seem weird?