EF 100-400 IS II USM

[CliveM]

I have not had this lens long but have an issue with the autofocus. If I extend the lens fully to 400mm it does not focus at all. Having recently been on a wildlife holiday where there were many 100-400mm lenses it appears I am the only one with this issue. If I first pre-focus on  shorter length it focuses OK then, and focuses when fully extended. This can't be right can it? Any thoughts before I return it to Canon?

[diverhank]

It doesn't sound right at all.  There is one thing to try:

On your camera menu, look for a magenta one...if there is an option called "Lens drive when AF impossible"...make sure that's set to ON which means the camera will continue focus search even when it thinks AF is not possible.  I find that the camera is not very smart it often thinks AF is impossible when it really is possible and just sits there doing nothing.

[Waddizzle]

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@CliveM wrote:

I have not had this lens long but have an issue with the autofocus. If I extend the lens fully to 400mm it does not focus at all. Having recently been on a wildlife holiday where there were many 100-400mm lenses it appears I am the only one with this issue. If I first pre-focus on  shorter length it focuses OK then, and focuses when fully extended. This can't be right can it? Any thoughts before I return it to Canon?

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Is this your fist super telephoto zoom lens?  What camera body, and AF focusing mode, are you using?

Using a super telephoto zoom can take a little getting used to, especially one that has focusing range switches.  Changing your focus from seven feet to seventy feet can tax the limits of your gear.  Remember, while the lens focuses, it is the camera body that controls the process, and that YOU control the camera body.

Sometimes when I am making a significant change of focusing distance, I will refocus in steps.  Instead of going from seven to seventy, I may focus on something halfway, or maybe two somethings, lite at 15 feet and then 30-40 feet.  I find this is frequently needed when I switch the focusing range switch, although not always.

[ebiggs1]

"This can't be right can it?"

No, it isn't but that doesn'tmean it is the lens' fault.

"Any thoughts before I return it to Canon?"

Yes, I do.  Two things to do first, One is reset your camera and try it outside on a sunny day.  Set the mode to P, ISO 400, AWB.  Make sure the lens is set to AF and the limiter off.  Second, try it on a different camera.  Repeat the 1st suggestion.

If either of these work, there isn't anything wrong with the lens. If neither works call Canon service.

[CliveM]

Dark here now in the UK so will try your suggestions first thing in the morning, even if it is snowing! Can you explain what you mean by the limiter? I can't find a reference to this in the manual.

Thanks for the prompt reply earlier.

[Waddizzle]

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@CliveM wrote:

Dark here now in the UK so will try your suggestions first thing in the morning, even if it is snowing! Can you explain what you mean by the limiter? I can't find a reference to this in the manual.

Thanks for the prompt reply earlier.

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He is referring to the focus range switch.  It “limits” the useable range of focusing distance, which allows for better focus resolving.

[CliveM]

Thanks for the reply. The body is a 5d mk4, and I have had many, many years of success with 28-300 and 30-350 in the past.

I have had to follow the step by step focus to get a sharp image at 400mm but the key point is 7 other similar lenses on a recent trip did not have this issue. Shooting wildlife, especially birds, this is not what I need. I usually leave the focus range on Full.  Clive

[CliveM]

Thanks Hank. It was set to off, so that is something else to try in the daylight tomorrow. Sometime it is not just the camera that is not too smart! Clive

[Waddizzle]

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@CliveM wrote:

Thanks for the reply. The body is a 5d mk4, and I have had many, many years of success with 28-300 and 30-350 in the past.

I have had to follow the step by step focus to get a sharp image at 400mm but the key point is 7 other similar lenses on a recent trip did not have this issue. Shooting wildlife, especially birds, this is not what I need. I usually leave the focus range on Full.  Clive

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I only use the Full setting for closeups.  The lens will focus faster and sharper with the 3 meter to infinity setting, on more distant objects.  This could be half the problem.  

The other half of the problem could be AF setting in the menus that you found.  But, if you have no problems with other lenses, then maybe not.

One last potential problem is a lens filter.  I used to use a B+W UV filter, and my photos always seemed a little soft.  I switched to a “Clear” filter, for protection, and I have been razor sharp ever since.  I use a clear protective filter on all of my lenses.

[Waddizzle]

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@CliveM wrote:

Thanks Hank. It was set to off, so that is something else to try in the daylight tomorrow. Sometime it is not just the camera that is not too smart! Clive

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The 5D mark IV has complex focusing system.  It work just as hard for you, as it can against you.  Others have posted links to special manuals on just the AF system.

I use AI Servo mode, with all of the AF points active, on my cameras bodies.  The AF points visibly track and move with subjects.  There are a variety of tracking modes you can use.  I have it set to always begin from the center AF point, and then use surrounding AF “assist” points as needed.  

Then there are the priority settings, focus priority or shutter priority. I use Focus Priority for all of them.   And, there is more.  It’s too complicated to describe all settings here, just what it looks like in the viewfinder.