Lens Focus Question

[Canonowner]

Hello

I'm new to this forum and have a question about an issue that I have time to time with my camera and lens I use for bird in flight photography.

Bird in flight photography is a new hobby for me since the Spring of this year and I use the Canon 100-400 version 2 lens on a Canon 40D body.

I have noticed a few times that when I completely lose focus on the bird while tracking it in the open sky with no obstructions, I have a hard time trying to get the camera /  lens to properly focus on the bird again.

I'm at the 400mm end of the focual length when this happens.

I can understand the camera and  lens having a hard time trying to refocus on a small object in the sky so, what I do is point the camera towards something on the ground like a tree or a building to try to bring things back into focus.

What I have noticed when doing this is, it takes many attempts to get the camera / lens to reacquire focus on the tree or building before I can even attempt to try and get focus on the bird again.

I'm still at the 400 end of focual range when doing this.

I have tried a couple of times to manually refocus the lens on the bird but, I have a hard time trying to find the bird again and I'm just not good at using this method at this point.

So my concern is, is this a normal issue for a situation like I've described, and if it isn't, what might possibly be the cause?

My thought is that maybe it's the AF system of the 40D.

The body is 9 years old and since BIF photography is new to me, I have no past experience that I can relate to for this kind of situation.

There are no AF issues at all with still objects.

I'm hoping that there are no issues with the lens.

I bought it brand new Sept. of last year.

If anyone has a possible explaination for why this happens, or how to prevent this from happening, it would be appreciated.

If this is of any help, my BIF settings are:

Back button focus.

AI servo mode.

High speed continuous shooting.

All focus points are active as I'm normally tracking the bird in open sky.

The lens focus range is set to 3m to infinity as the birds are always more than 3m away from me.

[Waddizzle]

"That's interesting that your method is to use all AF points for BIF photography with a busy background.

I'm not saying that it's the right or wrong method but any instructional videos for BIF photography I've watched, suggest that a busy background is when you do want to use the centre AF point only.

I understand your explanation for using all the AF points."

I do change up, depending upon the relative distances between the subject and background.  When the background is close to, or within, the DOF I will use just the center zone of AF points.  Or, just the center with four AF assist points.

However, the shot that I posted was with all AF points active.  The AF system can easily track the BIF when the background is outside of the DOF.  The real trick is getting the initial focus lock.

[ebiggs1]

"I have all 9 focus points active ..."

With your camera, I would use just the center point.  You know you still have MF. You can help the lens when it is struggling to obtain focus. If it is a small bird flying fast, it may be very difficult.

[Waddizzle]

“I'm new to this forum and have a question about an issue that I have time to time with my camera and lens I use for bird in flight photography.

Bird in flight photography is a new hobby for me since the Spring of this year and I use the Canon 100-400 version 2 lens on a Canon 40D body.”

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Sometimes lenses need a nudge on the focusing ring when you make a significant change your focus distance.

The lens has a focus range adjustment switch.  Set it for long range focusing.  For capturing BIF, I would use AI Servo focusing mode, with all AF points active.  The camera will want to focus on the nearest subject, so keep the subject within the area in the viewfinder covered by AF points.  This is where YOUR skill at tracking a moving subject come into play.  

This was taken with a 6D, which only has 11 AF points, and a Sigma 150-600mm “C” lens..

I am not familiar with the features of that camera body, but check to see if it has an Image Priority adjustment.  There would be two settings: First Image and Second Image.  These settings only kick in when you are in AI Servo and Continuous Shooting modes.  I suggest setting them both to full tilt Focus Priority, which will force the camera to lock focus before it activates the shutter.