Bird in flight technique question

[Mike Moynihan]

I was out shooting waterfowl today. With my 7d 2 and 100-400 2, I was getting very good, sharp images as they came into land. However, of the six or seven images taken per bird coming in, several were out of focus ( like 2 out of the seven). So my first 3 are fine, my next two out of focus and my last two in focus. I bump my focus as they come in, probably three or four times. When the duck gets low on the background, I end up focusing on the water and not the bird. Shaking due to my age probably has something to do with it (as well as being on one knee to get low). Here's my question, do I need to bump focus so much or will the autofocus system hold on the duck when it is coming in?
I'm using bbf, centre point focus, al servo, etc. ( following Art Morris' guide).
Thanks for the help.

[Steve Large]

Hi Mike,
Sounds to me like you ran into the same old snag that we all do. When the bird is too much like the background the camera can't figure out what to focus on. As you probably know the focus is dependant on contrast. If there is not sufficient contrast between your background and your subject it just doesn't always pick it up or will default to the overall background. I have the same problem in the winter with short-eared owls that fly over dead grass at the estuary. It becomes a bit hit and miss for sure. I too used to bump the focus more but have gone to holding the AF button down for the entire string of photos as it seems to hold the focus a bit longer once you have initially obtained it.

Steve

[Mike Moynihan]

Thanks Steve. I hear what you are saying. This morning I tried center point surround with the 4 additional focus sensors. Worked much better. I was also lower to the water which may have helped the contrast issue.

[Doug Brown]

Hi Mike. You might also try changing the focus case on your 7D2. Try Case 4 for birds that are accelerating or decelerating quickly. Also, BIF take lots of practice to get good at.

[arash_hazeghi]

shaking, i.e. unstable tracking will sure affect the focus. it can cause the focus to lock on the BG, and once it locks on the BG, the camera will have a slim chance of getting back on the duck in time for you to make the shot. use 4 or 8 sensor expansion and set the tracking sensitivity to slowest setting. Wait for the duck to come closer such that it is about twice the size of the center meter circle and then bump the focus and shoot a short burst and let go, you are more likely to get a few sharp frames than trying to bump constantly. If you are using back focus make sure you keep it pressed while pressing the shutter button.

Best

[Mike Moynihan]

Thanks again for the help. I'm going tomorrow morning and will be experimenting. I already changed to 4 pt expansion and do use back button focus. I did get some good shots with the expansion. I wasn't holding the button down all the time so I'll try that too.
i also am laying on my back in the marsh and sitting up to shoot - not always the most advantageous position to be in, but necessary to get close. Anyway, it is so nice being out in the marsh watching it come to life again.

[arash_hazeghi]

Thanks again for the help. I'm going tomorrow morning and will be experimenting. I already changed to 4 pt expansion and do use back button focus. I did get some good shots with the expansion. I wasn't holding the button down all the time so I'll try that too.
i also am laying on my back in the marsh and sitting up to shoot - not always the most advantageous position to be in, but necessary to get close. Anyway, it is so nice being out in the marsh watching it come to life again.

Mike, if you release the AF-ON button and then press the shutter button the camera will no longer focus in the delay time between releasing the AF-ON and the time shutter opens. In this time the duck will move and become OOF. For fast moving subject you need to keep the AF-ON button pressed to enable AI-servo focus tracking. The camera will then predict the subject's movement and account for that when the shutter opens.

For this reason I personally prefer to use the shutter button for focusing as well. pressing one button is easier for me than pressing two.

[Mike Moynihan]

I made it out this morning. I had to change location to get some action, but such is life. I was much more successful getting good focused shots throughout the approach. I waited a longer time before clicking away and did not bump focus as much. Arash, that's an interesting suggestion. When I switched to bbf I was quite impressed with the results because I couldn't find my release pt between focus and shutter. I'll have to try that again and see if my increased experience makes it more effective for me. Thank you.

[David Stephens]

For this reason I personally prefer to use the shutter button for focusing as well. pressing one button is easier for me than pressing two.

I also prefer this technique. I will lift off and bump the AF periodically and shoot in bursts of two or three, but the AF needs to be on for the AI Servo mode to function. Lots of people swear by back-button AF, but I prefer the single-button approach.

Dave