A few years ago, I learned a technique from Rob Sheppard to make sure the critical part of my subject is in focus. He suggested focusing precisely on the part of the image that must be sharp. From that starting point, I could then calculate depth of field (DOF) and determine what additional parts of the image would be acceptably in focus. In practice, I could also use the DOF preview button and see it real time. This technique is great for every type of photograph I make. It is sometimes a bit challenging though when photographing action.

In the example image, the eagle's eye must be sharp so it makes sense to focus precisely on the eye only. I can make that happen by selecting a single auto focus (AF) point, placing it on the eye, and tracking the bird as it flies from right to left, easier written than executed when the bird is moving very quickly.

Since this can be difficult, many photographers choose to use a zone AF system in which multiple AF points are active. As long as the subject is under one of the active points focus is normally achieved. This technique works well as long as there is sufficient DOF to cover from the point of focus (as determined by the zone) and the critical part of my image.

Looking at the example eagle again, notice the left wing tip is not sharp. The shutter speed of the shot is 1/1250th so motion blur is not the culprit, lack of DOF is. This demonstrates where the zone technique can hurt you. If the zone had "locked" onto the outer portion of the left wing it would be sharp, but the critical area, the eye, would not be. Fortunately, for this image I knew I had shallow DOF and needed to precisely place my single AF point on the bird's eye.

So what should you do in the field, single or zone? Single is much more challenging but it always works. The zone is much simpler but DOF can be an issue. I use both methods but before I shoot I calculate my DOF with a smart phone or tablet calculator. This way I begin the shoot with the information that allows me to choose the appropriate AF technique.

Approaching each action shoot whether birds, horses, or people, I follow the checklist shown below and always calculate my worst-case DOF so I know if I should use a single point or the zone.

More info on this checklist and many others may be found at the following link.

Checklists

Of course making the choice between zone and single point is just one part of the process fpr action photography. You must also practice your focus actuation technique, support, tracking, and exposure modification.

Very few eagles where I am in California so I practice on any and every bird I can find. If there are no birds around I make do with anything in the air. The shot below is a single AF point with the EF 800mm f/5.6L lens tracking a moth, needed a bit more shutter speed to freeze him.

When you are ready for eagles join Rick Sammon and me in Alaska and let's shoot!

Alaska!

There are many shots that require you to react extremely quickly in order to capture what you want such as these whales I photographed during one of my Alaska workshops. One of the most successful techniques you can use is what I call the "test shot."

The test shot has two primary objectives, exposure and rough focus. When taking a test shot your actual subject is usually not in the frame. For example, these whales break the surface in less than a second and if I wait until the subject is in the frame to find exposure I will be less than successful most of the time. If instead I anticipate where the subject will appear or what the event will look like, I can figure out exposure ahead of time very easily. I can also pre-focus so that the precision focus process is much faster once my subject is in frame and my auto focus sensors are properly placed.

*A humpback whale going for it in front of Devil's Thumb*

When you make a test shot, it is often times not adequate to set exposure based on the environment/background. You need to anticipate what will drive the exposure. For example, in all three whale shots the critical elements are the white water and the white fins/body. If I make a test shot of just the water and set exposure without considering the extreme tonal difference between water and white water/whale, I will, most likely, blow the highlights in the shot. When I made the test shots for these images, I set my exposure based on white not on the water/background. You can use rules of thumb to underexpose for the predicted highlights but I prefer actual meter data, when I can get it. In these examples, I changed my camera's metering mode to Spot and then I set exposure off of something white. I actually used the boat's wake but a white sheet of paper would work as well. As long as the white is under the same lighting conditions as my subject, my exposure will work perfectly.

This process is simpler when shooting in Manual exposure mode but can be used with Aperture or Shutter priority and auto exposure lock. Once I have my exposure, I pre-focus to the expected subject distance and take a test shot and evaluate. With my exposure and pre-focus set, I am much better prepared to quickly execute the actual shot when the action occurs.

I use test shots all the time to give myself the advantage when something might happen and my reactions have to be perfect. When I am out photographing, people find it odd that I am shooting every now and again at what appears to be nothing. But my "strange" behavior pays off. If you stack your deck ahead of time you will enjoy success in a more consistent and repeatable manner.

Fiat Lux!

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