Shooting Wildlife - Which Focus Mode?

Hi,

Most of my shots tend to be landscape rather than wildlife, but I went on a trip to one of our local nature reserves yesterday which is famed for it's red squirrels.

I got a few shots that I was happy with, but would appreciate advice on best focussing techniques to use when using a 20D to shoot wildlife running around in a wood.

I was setup in AI Servo, and left it set just to the centre point. I was having problems with losing focus lock, particularly when they were scurrying about amongst branches etc.

Do people find they get better results with all 9 AF points activated, might I have been better off with manual focus, or is this simply a hard situation to cope with whichever way it is done?

Any advice appreciated,

I use the center focus point but leave expansion on. I also tend to use single-shot and tickle the release rather than AI servo, but sometimes use servo instead.

- DL

Thanks Don, will give that a go.

How exactly does it work in this mode - does it always use the center point initially, but then move to the outer points if necessary?

AI Servo or AI Focus will only work if you keep your target right under a focus point. You can't focus and recompose with it at all.

So... I find that Single Shot works best when I have animals not moving around too much. For rapidly moving, I tend to go straight for AI Servo.

Branches are be problematic - as the squirrels ran along they probably had other branches get in your way from time to time. Suddenly it looks like the subject is much closer and the camera tries to focus on the branch instead of the squirrel. I've noticed this when birds fly behind grass or other obstacles. I don't have a recipe for avoiding this - I just wait until the bird is clear before I try to regain focus. Letting up on the shutter button so that the focus doesn't get too far out of whack saves time when you go to regain lock.

I do wish I could have 2 sets of presets that I could switch back and forth between easily. Swapping AF mode is a moderately slow process, since you have to look at the top of the camera to make sure you got it right.

Andrew Stannard said:

How exactly does it work in this mode - does it always use the center point initially, but then move to the outer points if necessary?

Click to expand...

You can set the expansion size with a CF. I set it to the smallest so it will add at most one (adjacent) focus point in case the center lands on a uncontrasted area.

- DL

Don Lashier said:

You can set the expansion size with a CF. I set it to the smallest so it will add at most one (adjacent) focus point in case the center lands on a uncontrasted area.

- DL

Click to expand...

Don, I think you are talking about a 1-series camera, which has variable expansion...and, I think, works in both one-stop and AI Servo.

The OP referenced a 20D. The 20D has either all points or single point AF. The 5D has that, plus (CF17-1) expansion of the active "hidden" points, but this is only active in AI Servo.

Below is a post I made on another forum, which points out the AF differences on using one-stop and AI Servo. While mainly addressing 1-series, good reference on AF modes is Westfall's white paper http://www.photoworkshop.com/canon/EOS_Digital.pdf

*******************************************

A lot of people, including myself, have said that when using the CF4=1/3 you can effectively get and control whether you are in 'one shot' or 'AI Servo' AF modes., i.e. if you set the camera in AI Servo, AF'd and release the '*' , you would get one shot, if you continued to hold the '*' in you got AI Servo. It recently struck me that there probably are small, yet significant, differences between these modes.

Over the last few days I have been pouring over user manuals, white papers, and forum post to try to figure this out. I think I am close, so I would like to post here what I think and get all of your confirmation or correction.

My understanding below is based on my use of the 20D and 5D, but should apply to most/all(?) xxD/xxxD cameras. Some should apply to the 1-series, but I suspect there are some differences, particularly in the expand acquisition are, and I do not have knowledge to address these differences...possibly someone could add their knowledge.

One shot

- With Automatic Focal Point Selection (AFPS) set, all focal points are active and the camera typically selects the closest 'subject(s)' with readable contrast. The focal points used illuminate and focus acquisition light goes on.

- With Manual Focal Point Selection (MFPS) set, only the selected point will attempt to achieve focus. It will illuminate to show the point used. If focus is acquired the light will go on steady, if it is not it will blink.

- AF assist lamp will fire if enabled.

- Canon recommends one-shot for maximum performance in extreme low-light situations. It can take as long as a full second to achieve focus in extreme low light situations without AF assistance. Even with AF assist, low-light AF will be slower than bright-light AF.

AI Servo

- With AFPS, all focal points but the center point will be turn off until focus is acquired. Once the subject is being tracked with the center point, all focal points will be activated and the subject will continue to be track whereever it moves within the focal coverage area. No focal points are illuminated. No acquisition light goes on if focus is acquired, however, it will blink if focus is not acquired or lost.

- With MFPS, only the point selected will attempt to acquire focus and only this point will be used for tracking. The focal point selected will light briefly at the start of AF. Acquisition light is same as AFPS.

- MFPS with expanded acquisition area (5D CF17=1) - When the center FP is selected, the 6 hidden 'Assist AF points' in the spot metering circle also become active (not sure if this includes the initial focus acquisition). Therefore, 7 AF points will track the subject.

- AF assist lamp will not fire.

- AF with AI Servo in very low-light may result in hunting and/or inability to achieve focus. In those cases, switching to one-stop will allow the camera to AF.

Conclusion

- with AFPS there is a major difference in initial focus aquisition between one shot and AI Servo. With one shot all points attempt to focus and the closest 'subject(s)' are used. With AI Servo, only the center point is used.

- with MFPS the two act very similar in initial focus (with an open question of whether the 5D hidden points are used).


As I said above, I would appreciate feed back.

Thanks for the continued responses. Am going to try and return with my new found knowledge!

Am already using '*' for focus and have found this a great help, but need more practice with releasing it when branches get in the way. With my rather slow sigma 70-300 it's a real pain when the lens starts to hunt for focus - normally seems to happen when whatever I'm taking photos of does something interesting!

John - Thanks for the detail in your post, have done some more hunting around myself and agree with your conlusions.


Cheers,

Would appreciate answer to....

In my post, I had one thing I was not really sure of. I am highlighting here, in hopes of a learned response.

"- MFPS with expanded acquisition area (5D CF17=1) - When the center FP is selected, the 6 hidden 'Assist AF points' in the spot metering circle also become active (not sure if this includes the initial focus acquisition). Therefore, 7 AF points will track the subject."

Thanks...JOHN

Hi, John:

We covered this topic in the EOS 5D White Paper:

http://www.robgalbraith.com/public_files/Canon_EOS_5D_White_Paper.pdf

"In AI Servo AF mode and with automatic AF point selection set, a total of fifteen AF points, including the six Supplemental AF points, will function automatically. As with previous cameras, focusing starts from the center AF point. If it cannot track the subject, the other AF points will help. The Supplemental AF points enhance subject tracking performance and enable a smoother transition from the center AF point to adjacent AF points. When C.Fn 17-1, AI Servo AF and the center AF point are set together, subject tracking is improved because the seven AF points within the spot metering circle will be active: the center AF point and the six Supplemental AF points."

Note that the Supplemental AF points are only available when C.Fn 17-1 is combined with AI Servo AF. They never function in One-Shot AF regardless of the C.Fn 17 setting. Also, the center AF point plus the six Supplemental AF points are active simultaneously for initial focus acquisition when the center AF point is manually selected, but not for automatic focusing point selection.

Hope this helps!

Best Regards,

Chuck Westfall
Director/Media & Customer Relationship
Camera Marketing Group/Canon U.S.A., Inc.

Chuck Westfall(Canon USA) said:

"...When C.Fn 17-1, AI Servo AF and the center AF point are set together, subject tracking is improved because the seven AF points within the spot metering circle will be active: the center AF point and the six Supplemental AF points."

Also, the center AF point plus the six Supplemental AF points are active simultaneously for initial focus acquisition when the center AF point is manually selected, but not for automatic focusing point selection.

Hope this helps!

Click to expand...

Thanks, Chuck. It helps a lot.

I had read the 5D white paper, but the quote above was the specific thing which was not clear to me. Did it function with the center point initially or only after center pt achieved AF for add'l tracking.

Your following statement clears it up. I will edit what I posted so it will be clear at first reading....<edit>...ooops, appears there is a time limit on editing.

John

To the original poster:

In addition to the excellent advice you've received, you might also consider assigning AF to the * button (I think it's CF4 on the 20D). My wife uses a 20D, and has CF4 set to 3 on my advice. It took her a little while to get used to (and I think there is a long thread at OPF on this topic), but now she sees the advantage and uses it this way all the time.