Login or Join Now

Upload your photos, chat, win prizes and much more

Username:
Password:
Remember Me

Can't Access your Account?

New to ePHOTOzine? Join ePHOTOzine for free!

Like 0

Autofocus problem using a 1.4x

Join Now

Join ePHOTOzine, the friendliest photography community.

Upload photos, chat with photographers, win prizes and much more for free!

canonfan46
3 Mar 2013 - 5:08 PM

Hi all,
I have a problem with a Canon 1.4x II extender so as usual I turn to the experts on Ephotozine.

I am using the following equipment:- Canon 7D, Canon 400mm f5.6 prime lens, Canon 70-200mm f2.8 L IS II, 1.4x extender.

I was out the other night photographing the moon using the 400mm prime with the 1.4x attached. Everything worked fine and I had some good images using autofocus with mirror lock-up enabled.

Today I had the same set up and was trying a bird shot. I disabled the mirror lock-up and when I tried the shot the autofocus would not come on. The back of the camera showed MF set.

I tried the 70-200 with the 1.4x attached and everything worked fine.

I repeatedly switched between the 400mm and the 70-200 but the autofocus would not work with the 400mm.
The autofocus also works normally when using the 400mm without the 1.4x.

Anyone any ideas on what the problem might be?

Last Modified By canonfan46 at 3 Mar 2013 - 5:20 PM
Sponsored Links
Sponsored Links 
3 Mar 2013 - 5:08 PM

Join ePHOTOzine for free and remove these adverts.

rogerfry
rogerfry e2 Member 8509 forum postsrogerfry vcard United Kingdom
3 Mar 2013 - 5:18 PM

The 7D wil only autofocus with apertures of 5.6 or less....by adding the convertor, you're effectively working with an f8 lens....so autofocus won't work.

Last Modified By rogerfry at 3 Mar 2013 - 5:19 PM
canonfan46
3 Mar 2013 - 5:23 PM

that can't be right, I have used it many times with f11 and smaller

KevinEllison
KevinEllison e2 Member 72507 forum postsKevinEllison vcard England
3 Mar 2013 - 5:35 PM

Doesn't a lens do its focussing with the widest aperture available to it, then snaps down to f11 (or whatever..) when you actually press the shutter..?

canonfan46
3 Mar 2013 - 5:39 PM

I do know that the 400mm with a 1.4x attached has a maximum aperture of f8 and the camera does not allow the setting of anything larger than f8, but the autofocus should work with f8 and smaller.

arhb
arhb e2 Member 72274 forum postsarhb vcard United Kingdom68 Constructive Critique Points
3 Mar 2013 - 5:39 PM

The 1D series are the only bodies that have usable AF with lens/tc set-ups above F5.6,
and the 400mm F5.6 will become F8 with the 1.4tc attached.

It is possible that your focus was set to infinity when you did your moon captures with the 7D - 400mm - 1.4tc,
making you think it was autofocusing?

Helpful Post! This post was flagged as helpful
rogerfry
rogerfry e2 Member 8509 forum postsrogerfry vcard United Kingdom
3 Mar 2013 - 5:39 PM

It;s not a question of the aperture you're using....it's the maximum aperture of the lens which is the important thing. For the autofocus to work, the max aperture needs to be 5.6 or less.

Helpful Post! This post was flagged as helpful
canonfan46
3 Mar 2013 - 5:41 PM

Yes I agree, the lens has a maximum aperture of f5.6 and the converter makes it a max of f8, but the autofocus should work at f8

justin c
justin c  104527 forum posts England36 Constructive Critique Points
3 Mar 2013 - 5:42 PM


Quote: but the autofocus should work with f8 and smaller.

Not on a 7D it won't, it will only work up to f5.6. The Canon 1 series camera's will auto focus at f8.

You're better off focusing manually on the moon anyway. Just enable Live View and set the magnification to 5x or 10x.

Last Modified By justin c at 3 Mar 2013 - 5:44 PM Helpful Post! This post was flagged as helpful
rogerfry
rogerfry e2 Member 8509 forum postsrogerfry vcard United Kingdom
3 Mar 2013 - 5:43 PM


Quote: Doesn't a lens do its focussing with the widest aperture available to it, then snaps down to f11 (or whatever..) when you actually press the shutter..?

.
That's correct.

Helpful Post! This post was flagged as helpful
lawbert
lawbert  71713 forum posts England15 Constructive Critique Points
3 Mar 2013 - 5:43 PM

Im guessing with the mirror lock up you were in live view.

The 400 5.6 L will not take a canon convertor at all without taping pins on the lens to retain AF

The 70-200 2.8 is designed to work with any canon convertor whilst retaining AF.

Helpful Post! This post was flagged as helpful
canonfan46
3 Mar 2013 - 5:47 PM

If you look at the last post to my portfolio you will see a photo of the moon. As you can see on the metadata, it was shot with the 400mm + 1.4x at an aperture of f16 and with autofocus.

I have used this set up many times and always with autofocus

lawbert
lawbert  71713 forum posts England15 Constructive Critique Points
3 Mar 2013 - 5:56 PM

It says manual exposure modeWink

canonfan46
3 Mar 2013 - 5:57 PM

manual exposure is not manual focusTongueWink

canonfan46
3 Mar 2013 - 5:59 PM

I have really poor eyesight close up and because of that I have never ever used manual focus, so I am now really puzzled by how I took that photo

Last Modified By canonfan46 at 3 Mar 2013 - 6:02 PM

Add a Comment

You must be a member to leave a comment

Username:
Password:
Remember me:
Un-tick this box if you want to login each time you visit.