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Focussing issue with 5D Mark III

crockny
Frequent Contributor

I am using my relatively new 5D Mark III with my old 400mm 5.6 lens for bird photography.  It often will not grab focus.  I have to manually focus closer before it focuses.  It doesn't seem to matter which distance setting I use on the lens.

 

So I am missing quite a few bird shots.  I have no problem when using my old 7D.

 

I don't know if this is a full-frame issue, my particular copy of the camera issue, the combination of lens and camera, or something in my setup, even though I followed an online tutorial for setting up the 5D Mark III for bird photography.

 

Anyone have experience with this issue?

 

 

1 ACCEPTED SOLUTION

diverhank
Respected Contributor

I have the 5d3 and the 400mm f/5.6L and often shoot with the combo and I never had any problems like yours.  There is one thing you should check...the option called "Lens drive when AF impossible" -purple AF4 - make sure this option is set to ON:continue focus search.  Setting it to off will often stall the focusing

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24 REPLIES 24

crockny
Frequent Contributor

1.  I never had this issue with the 7D so I don't think it's the lens.  But you are right - the focusing options are beyond belief on the 5D ... that's why I followed a birding tutorial when setting them.

 

2.  I use the center focus single spot except when close to a bird when I move the single spot around..

 

3.  I did have the "lens drive when autofocus impossible" set to "off".  I remember I had it on "on" but was getting blurry shots ... apparently you can't win ... !

 

 

TCampbell
Esteemed Contributor

@crockny wrote:

 

2.  I use the center focus single spot except when close to a bird when I move the single spot around..

 

 


If you are actually in "spot" mode then this is likely a problem (and possibly "the" problem that causes your lens to stall).

 

On the 5D III you can set the focus to use a single focus point but not in "spot" mode.   You can also use the point in "expanded" AF mode (the single point will borrow the points above, below, left, and right to assist in locking focus on that point) or you can use "surround" AF (it will use all 8 points adjacent to the selected point).  

 

But if you use "spot" mode then it will use a single point ... and a REDUCED size.  This is almost certainly not what you want for a bird-in-flight.

 

Suppose you are taking a close shot of a subject at an extremely low focal ratio (e.g. suppose I have Canon's 50mm f/1.2L lens and I'm using it at f/1.2 so my depth of field is extremely shallow).  You probably want accurate focus on the subject's eye but will let the focus fall off artistically for the rest of the shot.  In this situation you may want to make sure the camera focuses in on the structure in the iris of the subject's eye and absolutely nothing else... so you can set the camera to use the "spot" focus which will reduce the AF area -- pretty much guaranteeing that it will not try to focus on anything "near" the eye... just the actual eye.  That's a good reason to use the "reduced" AF area of "spot" focus mode.  Basically the "spot" mode is for situations where you have shallow depth of field and want to make sure it locks onto exactly the thing you want and nothing else.  If you have a broader depth of field then there's probably little point in using "spot" AF.

 

But in order to focus the camera has to be able to lock onto enough contrasty structure.  It probably can't do this for a bird-in-flight.  By expanding the focus area you let the camera get a larger section in order to find some good contrasty structure that can help it lock focus.   

 

I would try changing the focus mode either to expanded AF or surround AF.  Expanded AF is the mode that has 5 points in a "+" shape (technically it's a single point but it's "borrowing" the points above, below, left and right to make it easier to identify contrast and lock focus).  Surround AF is the mode that grabs the box of 9 focus points.  It really wants to focus on the center point but it is "borrowing" all 8 of the surrounding points.

 

There's also zone AF or the full auto-select (all AF points are fair game in that mode).  

 

It should have a much easier time locking focus if you give it a larger focus area.

 

Tim Campbell
5D III, 5D IV, 60Da

crockny
Frequent Contributor

Thanks for the explanation TCampbell!  I have always used single spot AF and have gotten very good flight shots with sharp eyes ... I tried other options but didn't see any improvement.  After your explanation I will try the expanded version again.

crockny
Frequent Contributor

So ... changing the "Lens drive when AF impossible" setting to On seems to have pretty much solved the problem.  I remember turning this off for some reason and then I didn't realize how badly it was affecting things.

 

Thanks everyone!

 

S

crockny
Frequent Contributor

Also TCampbell, since you seem to know your way around the autofocus maze ...

 

When I switch to back button focussing occasionally and look through the viewfinder I've lost my single spot focus and it does whatever it feels like!  Do you know how I can control this?

 

S