7D Mk II Fails to Focus in AI-Servo

[birdbrain]

What does it mean when it says, "if focus cannot be achieved"? I think you are suggesting the camera won't even try to move the focus motor if the AF unit in the camera determines that focus is not possible?

Correct. That has always been the problem of disabling focus search. If there is a strong defocusing so that the AF can't even determine the direction into which it has to move the focusing group AF won't even be attempted.

I think you are suggesting the low light, low contrast scene was responsible for the AF unit to not be able to find distance and direction information? If yes, then can you explain their recommendation for superteles?

The recommendation is made on the bases that you have been focusing at roughly the correct distance (that's why the supertelephoto lenses can recall a focus position on button press - to get you into that ballpark.

 

[WilbaW]

There is nothing in the opening post photo which requires AI Servo. There may have been something moving off in the distance but it does not appear to have been changing its focus distance appreciably as it moves.

AI Servo tells the camera that there IS such a subject and it keeps hunting for it to try and identify it. After all, it was TOLD there was something that needed AI Servo.

The Canon AF videos on the bhphotovideo website are interesting and very helpful. That is where I learned that AI Servo gets used wrong in this way and it causes problems.

Don't be so gullible. Spend the minute it would take to find the truth behind the claim before repeating it again. (See Don't Use AI Servo (continuous autofocus) with Static Subjects in Busted! Digital Photography Myths for more info.)

 

[KatManDEW]

I don't know how relavant it is to the the problem you are describing, but I had quite a bit of trouble with mine not focusing over the weekend when I switched from near to far subjects, in both AI Servo mode and One Shot mode. I've had this problem with several bodies, but it seemd to be more of a problem with the 7D2 over the weekend.

I overcome the problem buy bringing the focus" into range" with manual focus, which although not ideal, is a workable solution. Except that's a PITA when wearing gloves because I have trouble feeling for the focus ring without taking my eye away from the viewfinder.



I have to range on the lens set to "Full".

 

[Schwany]

I did not read all the replies, so ignore if mentioned.

Sounds like you might have had the lens focus limiter switch in a weird position by mistake, and had the camera set to not focus if impossible. But that is just a guess of course. Why 280mm, and not 560mm on the subject?? It might have focused if you'd zoomed in.

 

[KatManDEW]

I did not read all the replies, so ignore if mentioned.

Sounds like you might have had the lens focus limiter switch in a weird position by mistake, and had the camera set to not focus if impossible. But that is just a guess of course. Why 280mm, and not 560mm on the subject?? It might have focused if you'd zoomed in.

Focus limiter was set to "Full". I checked that a couple times, and switched it back and forth to see if it was somehow not engaged properly. I was at 560 mm. I just got this third body last Thursday and you just reminded me that I forgot to set "Lens drive when AF impossible" to OFF. Thanks for the reminder, and the reply.

 

[rickyred]

I am saying Yes.I the picture you posted, there is almost no contrast,very low light. AF is not a miracle worker. Some one else posted a picture of a blurry shirt. No contrast for the AF to lock on. I believe my 70-200 F4 might have had a chance to lock focus in the same conditions. After all I live in the North West United States and have become proficient at getting decent pictures in low light.

R.J

 

[Schwany]

I did not read all the replies, so ignore if mentioned.

Sounds like you might have had the lens focus limiter switch in a weird position by mistake, and had the camera set to not focus if impossible. But that is just a guess of course. Why 280mm, and not 560mm on the subject?? It might have focused if you'd zoomed in.

Focus limiter was set to "Full". I checked that a couple times, and switched it back and forth to see if it was somehow not engaged properly. I was at 560 mm. I just got this third body last Thursday and you just reminded me that I forgot to set "Lens drive when AF impossible" to OFF. Thanks for the reminder, and the reply.

Alrighty then. I was trying to reply to the OP riknash. I use the tree view, and it looks like my post is under his, but of course way down at the bottom of the page. Anyway...

riknash's shot was at 280mm with the 200-400f/4 according to the exif posted.

 

[Slideshow Bob]

I am saying Yes.I the picture you posted, there is almost no contrast,very low light. AF is not a miracle worker. Some one else posted a picture of a blurry shirt. No contrast for the AF to lock on. I believe my 70-200 F4 might have had a chance to lock focus in the same conditions. After all I live in the North West United States and have become proficient at getting decent pictures in low light.

R.J

1/1600sec, f/5.6, at ISO 6400 is not indicative of "very low light". Not by any stretch of the imagination. The 7DII's AF system will work down to -3ev, which is far less light than the posted shot was taken in.

 

[Ember42]

What does it mean when it says, "if focus cannot be achieved"? I think you are suggesting the camera won't even try to move the focus motor if the AF unit in the camera determines that focus is not possible?

Correct. That has always been the problem of disabling focus search. If there is a strong defocusing so that the AF can't even determine the direction into which it has to move the focusing group AF won't even be attempted.

I think you are suggesting the low light, low contrast scene was responsible for the AF unit to not be able to find distance and direction information? If yes, then can you explain their recommendation for superteles?

The recommendation is made on the bases that you have been focusing at roughly the correct distance (that's why the supertelephoto lenses can recall a focus position on button press - to get you into that ballpark.

 

[dhogaza]

I suspect that only holds if the camera is actually autofocusing the lens.

For instance, what would you expect to happen if you switched the lens to MF? That the AF focus priority choice for servo would prevent you from taking any photographs?

I'm totally with those suggesting that turning off the lens drive when AF can't be achieved is the cause of the "problem". I tried enabling that on my 7D with my 600/4 at one point and ran into exactly the same thing you mention, the lens wouldn't AF at all in some cases, totally confusing me. Allowing it to seek works better IMO.

Now, rather than disagreeing, why not turn that feature back on and see if the "problem" reappears?

My guess is it won't. If we're wrong, and it does, then the hive mind here can put its thinking cap back on.

Unfortunately, the pine marten probably won't reappear either, and your frustration is very understandable.

 

[jjss]

Me too. I don't remember when was the last time i use one shot for wildlife or birds unless i screw up or it was used by someone and forgot to set it back, and i never had any issues with AF continue in 1 series or AI servo in prosumer bodies.

AF servo is full time on my 7D2, and frankly, i can't get it to misfocus on stationary subjects.

As for OP, the AF search is OFF. That's rookies 101 mistake. Nothing wrong with the outcome here

What is AF search ? how to turn it on ?

 

[Karl Gnter Wnsch]

What is AF search ? how to turn it on ?

If you don't know what AF search is then probably you have never messed with the default setting - and thus it will be turned on (default setting). You have to explicitly disable it...

 

[jjss]

Thanks, found it in PAGE 122 of the manual