100-400mm f/4.5-5.6L IS II Auto Focusing Behavior

I'm still learning the 100-400mm, and I took it to the zoo today for a lazy man's safari.

Here is a strange behavior I've not seen on my Canon lenses unless I'm in a very dim shooting environment, but the lens refused to auto focus quite a few times on my 5D IV. The outdoor temperature was in the 20s-30s, but the light was there, with subjects all had good contrasts. In all cases, the AF dot blinked and indicated the camera wasn't able to AF. However, AF would then start to work after I manually moved the focus ring close to actual focusing plane. Is this a trait of this lens? It is a f/5.6 lens, but it was no less than EV-11 to EV-12.

I ran that lens on a 7DII for about two years without issue.

I have also been using it on a 1DXII with 1.4EX and sometimes the AF stops completely ... I need to turn the focus ring a fair way in order for lens to start AF again. I have been meaning to try without the extender to see if that might be the issue.

Sounds like might be something similar to what you are experiencing, though I am shooting outdoors in good light,

There are a couple of things you could check...

1. Did you have the lens set to focus from 3m to infinity ?? I've forgotten to check that myself a few times !

2. AI Servo 1st/2nd image priority settings which affect the balance between focussing and release timing

Rose

Please check your camera AF settings - there are two modes when AF is impossible

- on: continue to search - which is the one you should chose

- off: stop focus search

I`m pretty skure this will fix your issue - please let me know.

ffabrici said:

Please check your camera AF settings - there are two modes when AF is impossible

- on: continue to search - which is the one you should chose

- off: stop focus search

I`m pretty skure this will fix your issue - please let me know.

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Yes, I did have the setting of not to hunt when AF is not possible. I guess I was not expecting how an f/5.6 lens would not AF in many conditions all seem not difficult with my other Canon lenses. Thanks for the suggestion.

Maybe I should reenable AF searching, as it removes my manual focusing evolvement. It is just I do not like this behavior when shooting lowlight sports.

When a long tele is way out of focus, the AF system is totally off track and can’t achieve focus if you don’t allow it to start searching. If the AF is too nervous then change the AF program in stead.

ffabrici said:

When a long tele is way out of focus, the AF system is totally off track and can’t achieve focus if you don’t allow it to start searching. If the AF is too nervous then change the AF program in stead.

Click to expand...

Your description totally matched my experience. I just never seen such behavior with my 400mm prime, but their designs might be entirely different.

Ray Chen said:

I'm still learning the 100-400mm, and I took it to the zoo today for a lazy man's safari.

Here is a strange behavior I've not seen on my Canon lenses unless I'm in a very dim shooting environment, but the lens refused to auto focus quite a few times on my 5D IV. The outdoor temperature was in the 20s-30s, but the light was there, with subjects all had good contrasts. In all cases, the AF dot blinked and indicated the camera wasn't able to AF. However, AF would then start to work after I manually moved the focus ring close to actual focusing plane. Is this a trait of this lens? It is a f/5.6 lens, but it was no less than EV-11 to EV-12.

Click to expand...

I have only experienced this when the Focus Limiter Switch is in the wrong position on the lens. On one occasion (also at a zoo) the lens was attempting to focus on a reflection on the glass rather than the subject behind it. With some lenses, standing near a power transformer for a neon sign will trigger a malfunction (usually a freeze) on a lens/camera combo. In my experience, when a reflection highlight (eg sparkling sunlight on water) falls out of focus the camera will throw the focus completely out because the sharp edges of the bokeh seem fool the sensor into thinking that the subject is in focus.
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Do you use a Filter on your lens? The use of a low quality, non-Digital UV filter will cause focus problems with this lens. It also occurred with the Mk1 version of the lens as well. I used this lens on the new EOSM6 mirrorless camera and found it to be a little sluggish and it also produced a strange streaking effect in the images. The advice from others who experienced the same was to make sure the filter I was using was a good one. I had accidentally left a cheap UV filter on my lens that day, thinking I was to be shooting in the salt air of a beach. Getting rid of that filter and using a quality Hoya Pro1 MC UV [O] filter on this lens eliminated all the issues instantly.
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On my Full Frame cameras (it's usually seated on a 6D Mk1) this lens is flawless. On the newer DSLRs and EOSM cameras with DPAF sensors this lens performs equally well. The image quality and performance should be top notch.
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Check your lens/camera contacts and be sure they're clean. Use a rubber gum/putty or an alcohol solution if they look to have oils on them. I don't know the history of your camera or your lens but if either of them are second-hand, then this might be the reason the seller sold them on.
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The problem you described is not typical of the lens and this is the first time I have heard of this complaint.

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Regards,
Marco Nero.

Marco Nero said:

I have only experienced this when the Focus Limiter Switch is in the wrong position on the lens.

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It was checked and was at full range. Also not all malfunctioning cases were close to MFD.

Marco Nero said:

On one occasion (also at a zoo) the lens was attempting to focus on a reflection on the glass rather than the subject behind it. With some lenses, standing near a power transformer for a neon sign will trigger a malfunction (usually a freeze) on a lens/camera combo. In my experience, when a reflection highlight (eg sparkling sunlight on water) falls out of focus the camera will throw the focus completely out because the sharp edges of the bokeh seem fool the sensor into thinking that the subject is in focus.

Click to expand...

As far as I know, all scenes have good contrast. It's either within shadows or directly lit by partial sun. No large reflective object in frame.

Marco Nero said:

Do you use a Filter on your lens? The use of a low quality, non-Digital UV filter will cause focus problems with this lens. It also occurred with the Mk1 version of the lens as well. I used this lens on the new EOSM6 mirrorless camera and found it to be a little sluggish and it also produced a strange streaking effect in the images. The advice from others who experienced the same was to make sure the filter I was using was a good one. I had accidentally left a cheap UV filter on my lens that day, thinking I was to be shooting in the salt air of a beach. Getting rid of that filter and using a quality Hoya Pro1 MC UV [O] filter on this lens eliminated all the issues instantly.

Click to expand...

I did have B+W 77mm XS-Pro Clear MRC-Nano 007 filter, but the lens would auto focus after I manually moved the focusing closer to intended focal plane. It appears the lens wouldn't AF when the it was "too far" out of focus, which I've never seen on my other Canon lenses.

Marco Nero said:

Check your lens/camera contacts and be sure they're clean. Use a rubber gum/putty or an alcohol solution if they look to have oils on them. I don't know the history of your camera or your lens but if either of them are second-hand, then this might be the reason the seller sold them on.

Click to expand...

Worth a check. It was bought new directly from Canon and on its second outing.

In short, switch off hunting because you don't want the lens to do that as it may take long before focus is acquired and sometimes it isn't even possible.

In practice it is much faster to 'help' the lens with MF when it can't find the subject.

Just make a rough estimate with a quick turn of the focus ring and then activate AF.