7D MKII Autofocus issue

Hi all,

Can anyone point me in the correct direction for this?

I have an issue that when I'm focusing on a static object (bird on tree, owl on ground etc) my autofocus will continue to jump around even though the centre is focused on the subject. If does the same thing when I'm trying to focus on a duck in water. It keeps changing focus to the waves and not staying on the duck.

I'm using the Sigma 150-600 S.

Thanks

Keep in mind that the autofocus sensor is actually larger than indicated by the marks you see through the view finder. If you're subject is rather small in the frame, it's very possible that the autofocus may grab onto something in the area surrounding your subject (such as waves around a water bird). It may also help to shoot in One Shot focus mode for static subjects because once focus is achieved, it won't continue to hunt, giving you time to assess the viewfinder and see if you're happy with the focal plane.

A few details needed:
What AF mode are you using (single point, zone, etc)
Are you using AI Servo?
How far away are your subjects?
Have you changed any of the Custom Settings in your camera yet? If so, which ones?

You do have the ability to change the sizes of the zones...single point, a few points, a smallish square area of points, a whole zone of points
The camera unfortunately cannot do "Do What I Mean" and it needs help in better selecting the target of primary interest in the photographer's mind.

I use AI Servo, and use full AP points as I need to track flying birds and find it would be the best way of doing that. I have updated some AF settings (I followed a guide online for BIF).

My subjects can be from 30 ft to 100 ft away. I assume now that when they are further away it will tend to jump around more.

CDN_Merlin wrote in post #18505114
I use AI Servo, and use full AP points as I need to track flying birds and find it would be the best way of doing that. I have updated some AF settings (I followed a guide online for BIF).

Using all points is your general root issue there; as Wilt mentions above, the cameras are rather 'dumb' when it comes to focusing.Using all af points, effectively, tells the camera "focus on whatever you can see the best", which is rarely the intended subject when there is a lot of clutter in the frame.

When you're shooting things perched, shoot single point and use the expanded or zone areas for your bif shots and you should see better results.

AI Servo further feeds into you issue with static subjects, because it never truly *locks* focus the way one shot does. It is constantly evaluating the scene while active, which triggers the focus change once it finds better contrast under another af point. This is not to discourage using AI Servo (I rarely use anything else) but just to give you the info on what it's doing.

Managing which af point or points the camera is using is your key to better success; that and working on your technique to keep the proper points on your subject.

Thanks. I'll go through my settings tonight and try it again this weekend to see if it works better.

I made the changes to my autofocus points last night and will test out this weekend. I always thought that using all 65 points would be best as it would only focus on what was in the middle but live and learn right?

Thanks for the help.

CDN_Merlin wrote in post #18505811
I made the changes to my autofocus points last night and will test out this weekend. I always thought that using all 65 points would be best as it would only focus on what was in the middle but live and learn right?

Thanks for the help.

Good luck; let us know how it works out for you!

CDN_Merlin wrote in post #18505811
I always thought that using all 65 points would be best as it would only focus on what was in the middle but live and learn right?

Wouldn't be much point in having the outer points if the camera always used the inner ones

The camera is dumb. It assumes that if you select AF points you want to use them and it will lock focus on the nearest thing that falls under one of the AF points..... which will likely be water if shooting a duck sitting on water.

If you want the camera to only focus on what's in the middle of the frame you should use a single focus point in the center of the screen. By using all points you're telling the camera to look across the entire frame and focus on the closest object with enough contrast to focus on (like the peak of a wave for example). Also helps to have your case settings such that the focus stays locked rather than bouncing around while you try to track a BIF behind obstacles, etc.

-Joe

Your camera is broken. I'll give you $25 for it.

unless your subject fill up much of the frame or the background is clean. maybe using Zone AF or Wide Zone AF is better than using all Auto AF 65 points.

Have you seen this page by Canon, along with a PDF you can download?

http://learn.usa.canon​.com …os7dmk2_afGuide​book.shtml

Sold, 25$ plus $3000 for shipping.