Why won't canon lens fully work in autofocus.?

[sphotocastle]

Canon lens 28-105mm attached to 5dmarkiii body will not always work in auto focus mode. I think I can occasionally get it to work in alfocus but even in manual the lens occasionally won't register focused objects. Do I have a problem with the lens or do I need to change a setting somewhere to get the camera to know what lens is on it?

[ebiggs1]

Not having your camera and lens in hand. I will still submit the lens is at fault not the 5D Mk III.  This lens is one of the poorer lenses made by Canon.  It is no longer made and has been discontinued for good reason.

Try a different lens on the 5D and see if it works better.

[JonKline]

Assuming you have the switch on the lens set to AF, and the camera set to use AF, that's all you should need to do.

I would suggest you send your lens in for servicing.

[RobertTheFat]

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@JonKline wrote:

Assuming you have the switch on the lens set to AF, and the camera set to use AF, that's all you should need to do.

I would suggest you send your lens in for servicing.

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Ah, this thread brings back memories. The 28-105 was my first lens on my first DSLR. I still have it, though it now resides on the sparest of my spare cameras (the one that goes to the first grandchild that shows any interest in a camera that's not part of a cell phone). It's not nearly as bad as Ernie Biggs makes it out to be, and I got some good pictures with it. But if it broke, I wouldn't pay actual money to have it serviced.

And I wouldn't dream of insulting my 5D3 by using that lens on it.