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FORUMS Canon Cameras, Lenses & Accessories Canon EOS Digital Cameras 
Thread started 12 Sep 2010 (Sunday) 20:25
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7D center focus w/ expansion? For tracking birds.

2,161 posts
Likes: 3
Joined Feb 2004
Location: PA USA
Sep 12, 2010 20:25 |  #1

Hey guys -

I am on vacation near bird sanctuaries and will be focusing on (no pun) using my 7D with 500mm F/4L. I am getting the hang of shooting hand held with this lens and read on the Bird section some guys are using center point with expansion - how's that work/enabled? That sounds better than just the center point which is what I am using now. I am also going to try and turn my AI-Servo sensitivity to slow because right now its rocketing in and out when I move off the bird (which happens easily with a 500mm + 1.6X crop!).

Thanks all

7NE | 7D | 5DII | 16-35/2.8L II | 24/1.4L II | TS-E 24/3.5L II | 50/1.4 | 85/1.2L II | 100/2.8L IS | 70-200/2.8L IS II | 400/5.6L | PIXMA Pro 9500 Mark II
check my blog: (external link)

3,514 posts
Likes: 15
Joined Oct 2007
Location: Australia
Sep 12, 2010 20:46 |  #2

Using a 400 F/5.6 I've been using centre point spot (or whatever it's called - the real small one) for static stuff. It does depend on how large the bird is in your frame though, if you can get nice and close and fill the frame then centre point or expanded might work fine.

I use the whole centre zone for BIF. For BIF I did have the sensitivity down a bit, but with the whole zone in use there was always a spot that would pick the bird up so it hasn't caused a real issue thus far.

128 posts
Likes: 5
Joined Apr 2010
Location: Montana
Sep 12, 2010 21:00 |  #3


You'll find your answer in this...‘C.Fn III: Autofocus/Drive.’ Some of these settings are among the most important of all 7D settings when it comes to getting the best possible images. I have ‘C.Fn III 1 AI Servo tracking sensitivity’ set to ‘Slow.’ If I’m tracking a flying bird and it flies behind a tree, slow tracking sensitivity means the camera will not give up focus on the bird and grab focus on the tree. This setting makes the AF much less twitchy. I have ‘C.Fn III 6 Select AF area selec. mode’ enabled. If you then select ‘Register’ you can place check marks next to the types of AF you use. Once you have your check marks finished you select ‘Apply’ to finalize your selections. To me this is probably the most critical setting of all. I have both of the automatic focus point selection options unchecked (these are the first 2 choices on the menu). If you want your images to be critically sharp where you want them to be sharp, don’t rely on the camera to choose your focus point for you. Using these 2 focus options is akin to shooting in full auto mode in my opinion, and is the cause of many out of focus images being posted on the internet forums. I have the last 3 AF options enabled (’AF point expansion,’ ‘Single point AF,’ and ‘Spot AF.’ You can cycle through the active focus modes by pressing the top right button on the back of the camera and then repeatedly pressing the M-Fn button just behind the shutter release button. I use ‘AF point expansion’ and ‘Single point AF’ for birds in flight. ’Spot AF’ is a more precise version of ‘Single point AF;’ it’s like an AF point within an AF point. I use it for perched subjects when I want to get the eye sharp. When using Single point and Spot AF, I often move the focus point around the frame in an attempt to compose correctly through the viewfinder (if a duck is moving across the water from my right to my left, I will move my focus point above and to the left of center and try to place the focus point on the bird’s eye). The next setting I alter is ‘C.Fn III 12 Orientation linked AF point.’ I have it set to ‘Select different AF points.’ With this setting, I can select both an AF mode and an AF point for the camera to use depending on whether the camera is in a horizontal or vertical orientation; the camera senses its own position and makes the adjustments automatically.

This was taken from Doug Brown's article at http://www.deepgreenph​​226 (external link)

Wildlife & Nature Blog @ His Creation (external link)

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7D center focus w/ expansion? For tracking birds.
FORUMS Canon Cameras, Lenses & Accessories Canon EOS Digital Cameras 
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