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VIP
Posts: 8,022
Registered: ‎12-07-2012

Re: 70-200 f2.8 AF problem

Still think it might be the camera. 

Whenever a camera seems to be doing something strange (or not doing what it should) it's worth a try to use the 'restore all settings to factory' option.  The lens doesn't know when it is in focus.  The camera does.  You may have a C.Function set incorrectly.

 

Besides that it could be you.  The scene you are trying to shoot.  No contrast, too dark, too close, etc, for instance.

A lot of Canon stuff. Along with, a lot of other stuff.
Esteemed Contributor
Posts: 3,628
Registered: ‎06-25-2014

Re: 70-200 f2.8 AF problem


ebiggs1 wrote:

Still think it might be the camera. 

Whenever a camera seems to be doing something strange (or not doing what it should) it's worth a try to use the 'restore all settings to factory' option.  The lens doesn't know when it is in focus.  The camera does.  You may have a C.Function set incorrectly.

 

Besides that it could be you.  The scene you are trying to shoot.  No contrast, too dark, too close, etc, for instance.


And I still think it might be cured with AFMA (assuming that the camera isn't a Rebel). The nice thing about AFMA is that it doesn't matter whether the problem is in the camera or the lens. It treats the symptom, not the disease.

Bob
Boston, Massachusetts USA
Respected Contributor
Posts: 1,918
Registered: ‎02-17-2016

Re: 70-200 f2.8 AF problem

Except the problem is not that the focus is off, it just can't focus, it hunts.

 

It looks to me that for some reason there is a lot of play in the AF connection to the focusing elements at 25 ft distances.

Occasional Contributor
Posts: 14
Registered: ‎07-24-2017

Re: 70-200 f2.8 AF problem

You guys have way more knowledge about this stuff than I do.  What is AFMA?  And when you say "a lot of play in the AF connection to the focusing elements", is that something in the lens itself?  Moot points since the lens is in the mail to the Canon repair facility...just curious.

Respected Contributor
Posts: 1,771
Registered: ‎02-26-2015

Re: 70-200 f2.8 AF problem


mish757 wrote:

You guys have way more knowledge about this stuff than I do.  What is AFMA?  And when you say "a lot of play in the AF connection to the focusing elements", is that something in the lens itself?  Moot points since the lens is in the mail to the Canon repair facility...just curious.


AFMA is used when a lens is focusing, but, either front or back focusing instead of accurately focusing. Since your lens was having difficulty focusing at all, I doubt AFMA would have fixed your issue.

Occasional Contributor
Posts: 14
Registered: ‎07-24-2017

Re: 70-200 f2.8 AF problem

Thanks, TT.  I think you're right.  It's not that it was focusing and the image was coming out blurry, it wouldn't focus at all on the closer subjects.  When it focussed on a more distant subject, the image was sharp.

Esteemed Contributor
Posts: 3,628
Registered: ‎06-25-2014

Re: 70-200 f2.8 AF problem


mish757 wrote:

You guys have way more knowledge about this stuff than I do.  What is AFMA?  And when you say "a lot of play in the AF connection to the focusing elements", is that something in the lens itself?  Moot points since the lens is in the mail to the Canon repair facility...just curious.


We're just thinking out loud. You're doing what we'd probably do if we were in your shoes.

 

AFMA is "autofocus microadjustment". It's a method of calibrating the accuracy of the AF mechanism. Most higher-level Canon cameras have it. The Rebels don't. If your camera has it, it's described in the instruction manual.

Bob
Boston, Massachusetts USA
VIP
Posts: 8,022
Registered: ‎12-07-2012

Re: 70-200 f2.8 AF problem

Robert from B Town, it ain't AFMA.  It might be a C. Func., though.

A lot of Canon stuff. Along with, a lot of other stuff.
Esteemed Contributor
Posts: 3,048
Registered: ‎06-11-2013

Re: 70-200 f2.8 AF problem

It sounds like your lens needs service.

 

If you focus the lens manually, is the focus able to move freely from closest focus to infinity?

 

Note that "L" series lenses with USM focus have a clutch which allows the focus mechanism to slip against the rotation of the focus ring on the lens barrel.  So you'd probably want to look through the lens or watch the focus distance scale in the window move as you rotate the focus ring.  

 

You're looking to see if it has the full range of focus range without sticking or jamming.

 

Tim Campbell
5D III, 5D IV, 60Da
Honored Contributor
Posts: 5,246
Registered: ‎08-13-2015

Re: 70-200 f2.8 AF problem

Two questions:

 

!.  Are you able to focus the lens manually at those ranges?

2.  If you have a filter on your lens, remove it.  That's one less question mark in the problem.

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