Rear focusing or back button focusing can come out very handy in wildlife photography! What is rear focusing???
This technique is not very well known, yet it is an effective way to combine ONE SHOT focus mode with AI SERVO mode. One presses the AF-ON or * back button with the thumb from the back of the camera (hence the name rear focusing) to obtain focus and metering, while the shot is only taken when the shutter button is fully pushed down with your index. Yes, one needs to use two fingers instead of one. Why complicating things?
This topic recently came back to my mind as I was attending a round table with the Tampa Area Professional Photographers Association (TAPPA), of which I am now a member! 🙂 Check out what they do and join if you live close.
To me there are two main advantages of back-button AF:
1. One can create effective stitches with multiple photographs as the technique meters only once. For instance, while being in AI SERVO mode, acquire focus and meter by pressing the back button with your thumb, take a first shot with your index, then release the back button, move your camera to the side or desired area to add to the first picture taken, then press with your index to take a second shot, third, etc… You have metered only the first time you acquired focus with the back button and the white balance and exposure level (meter) will not change until you press again the back button.
2. Focusing with the back button tends to track moving subjects a tad better, as you don’t lose the tracking mode when pressing with the index. When you track in the traditional way, by half pressing with your index, one sometimes loses the tracking once the shutter fully pressed.
Another advantage is that you can stop tracking with an undesired object comes in front of your focused subject and you can still take a few shots while this is happening without losing the focus you had locked in the first subject. This is useful in sports photography when the referee passes in front of the subject you are tracking.
Canon did a good job at explaining the technique in their back button AF article.
The photograph below is a Royal Tern with breeding plumage made out of two stitched photographs.
I am actually not overly thrilled with this creation. Why? The Royal Tern could have used a bit more space to the right side. In other words, I should have taken 3 or 4 vertical shots instead of 2 horizontal ones…
Do not forget to check out the fantastic African safari tour I will be leading next year! Join me to the BOTSWANA & VICTORIA FALLS PHOTOGRAPHY TOUR next September 2014! I will teach you step by step how to create the best photos. From beginners to professionals.
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