6D with old L series lens issue

[KiwiStu]

Hi. I have an EOS 6D mark 1 (which I love) and am trying to use an old 'L' series lens (70-200mm EF). In manual focus mode it works fine, but when I try to get it to auto-focus it will continually hunt, but never lock onto a subject. This is true whether the subject is moving or not. I've tried using different auto-focus points but doesn't help.

Is there a chance the lens is not compatible? Is it something I could calibrate myself?

Cheers,

Stu

[MikeSowsun]

Canon has always been very good at making their cameras, lenses, flash units, and accessories  backward and forward compatible. Even the very first EF lenses from 1987 are fully compatible with the latest cameras.

If your lens is not working properly, it is probably the fault of the lens, and would not be caused by the difference in the ages of the camera and lens.

[KiwiStu]

Thanks Mike. I should have added that the L lens works fine with my old 350D, AF locks quickly without any hunting. I've heard that is possible to calibrate lenses but not sure if that is relevant here or if it would help?

Cheers

Stu

[MikeSowsun]

If the lens works well with another camera, it may just be a communication issue. Try cleaning the contacts on both the lens and the camera.

[ebiggs1]

"Try cleaning the contacts on both the lens and the camera."

This will probably not help since it never to rarely does. But since it is easy to do give it a try.  Don't clean the camera.  You said it was working fine with other lenses so it doesn't have a problem. Denatured alcohol and a Q-tip and be gentle.

When you try to use the old lens make sure you have vertical lines in the subject.  Older lenses need this.  Good light not indoors.

[RobertTheFat]

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@ebiggs1 wrote:

"Try cleaning the contacts on both the lens and the camera."

This will probably not help since it never to rarely does. But since it is easy to do give it a try.  Don't clean the camera.  You said it was working fine with other lenses so it doesn't have a problem. Denatured alcohol and a Q-tip and be gentle. ...

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Very sound advice. But almost any alcohol will do, the purer the better. Even unflavored vodka can suffice, although it usually contains a lot of water, so you'd have to be careful not to let it get inside the camera. Remember what "denatured" alcohol is: simply ethyl alcohol (concentrated vodka) to which adulterants have been added to make it undrinkable.

[MikeSowsun]

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@ebiggs1 wrote:

When you try to use the old lens make sure you have vertical lines in the subject.  Older lenses need this.  Good light not indoors.

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Older cameras, without cross type AF sensors, needed vertical lines to focus on, but this does not apply to lenses. The lens just responds to AF commands from the camera. 

[ebiggs1]

"The lens just responds to AF commands from the camera."

 A horizontal sensor can read vertical lines but not horizontal ones; a vertical sensor can read horizontal lines but not vertical ones.  A cross-type sensor, as you might suspect, can read both horizontal and vertical lines and thus is able to focus on a much greater number of subjects.  However my point was and is make sure there is contrast in the subject which is provided by strong vertical lines in the picture. A fence for instance.

[TCampbell]

One posible cause can be focus distance and the range selection.  How close is your subject?

There's a switch on the side of the lens barrel that controls the focus range.  The two settings are 1.4m-∞ and 2.5-∞.   If you have it on the 2.5m setting, then it wont focus on anything closer... forcing it to "hunt".