I’m a firm believer that photography is a game of inches. So today I’ll share with you what I’ve learned about mastering autofocus shooting in a variety of difficult situations.
1. Continuous vs Single Autofocus
Knowing when to use Continuous (a.k.a. AF-C and AI-SERVO) or Single (a.k.a. AF-S and Single Shot) is the first step to mastering autofocus.
Single autofocus is great for still subjects. That’s because the autofocus operation will stop when the camera confirms autofocus on the subject under the focus point. You’re then free to recompose while the subject is in focus (as long as the distance between you doesn’t change).
On the other hand, continuous autofocus will continue to try to focus on whatever subject is under the chosen focus point. Moving subjects are perfect for this mode. Subjects that are still may cause continuous autofocus to “hunt” as it continues to search for movement where there is none. This can result in out of focus images.
It also isn’t the best choice for “focus and recompose” photography—unless you switch to back button autofocus (see below). That’s because when you move the camera to recompose, the focus point will no longer be on where you want to focus.
2. Switch to Back Button Autofocus
Activating the shutter and starting/stopping autofocus are very different functions, so why have one button to do both?
I first learned about back button autofocus technique from the book The Passionate Photographer. Master autofocus by assigning autofocus operations to a button other than the shutter release.
By allowing me to control autofocus activation, I’m able to effectively use the focus and recompose technique even when in continuous autofocus mode. That’s because I can press the back button to focus and then release it to stop autofocus operation. If I recompose after releasing the button, the focus won’t change.
Getting the timing right when you’re moving fast can be difficult. Using AF-ON allows you to have both continuous and single autofocus at the same time.
3. Focus Mode Quickchange
Being able to change between continuous and single autofocus with one button is a game-changer.
In addition to back button autofocus, I’ve customized my Canon cameras so that the depth-of-field preview button switches between AI-SERVO and SINGLE modes instantaneously. This gives me even more accuracy when my subject isn’t changing his/her distance from the camera (even if they’re still moving).
Unfortunately, I haven’t found a way to do this with my Nikon cameras. They do have a button that would be perfect for this, but as far as I’ve been able to figure out, you can only change between the two by pressing the button and using a command dial.
This is why I believe ergonomics are more important than other considerations when choosing a camera.
4. Aim for Contrast
Cameras like to focus on objects that have contrast. That could be contrast in the object itself, or in the way light is hitting the object (or both).
For example, I find it’s difficult to track focus on garments that are a constant tone in shadow. However, garments that have a pattern of lights and darks are easy—especially black and white patterns.
5. Use Only Cross-type Points
Cameras today come with a lot of autofocus points (153 is the current record on the Nikon D5)—thing is, not all points are created equal. Cross-type points are sensitive both horizontally and vertically, making them more accurate.
I customize my cameras so that I only choose the cross-type autofocus points. This allows me to move to the point I want faster using the joystick while trusting that I’ll get the shot in focus.
In fact, even if I owned the D5 with 99 cross-type points, I wouldn’t want to be able to pick every point. That’s just so I could switch the points faster. Why do I switch points? That’s so I can minimize my focus and recompose distance (below).
6. Minimize Focus/Recompose
Since I often shoot with a shallow depth of field, it’s important that I minimize the distance that I recompose. That’s because recomposing actually changes the angle of the plane of focus which could cause the subject to be slightly front or back-focussed. This is especially important at close distances.
So I need to pick a focus point that is closest to the part of the subject I want in focus. This way, I’m stacking the deck in my favour.
7. Choose the Center Point
What? Didn’t I just say that I switch focus points? I do, except when I’m faced with a situation where the camera may have trouble focusing. Things like:
- Low light scenarios
- Backlit subjects
- Fast moving subjects
- Subjects moving unpredictably
- Small subjects in a large frame
In all of these cases, I’ll use the center focus point as it is the fastest and most accurate. That’s because it’s often dual cross-type, meaning it’s sensitive to vertical, horizontal and two opposite diagonal lines.
I’ll then crop in post to get the composition I want.
Prefocusing on an area you know your subject will move through is helpful in a number of cases:
- When you are tied to a specific composition and can’t track a moving target through the frame
- If you know your subject will be passing by a stationary object in the frame
- When your subject is small and far away from the camera
- If your subject is moving parallel to the focus plane (see below)
My advice for this technique is to use a smaller aperture to increase your depth of field. Also, a focus target can be helpful here.
9. Keep Movements Parallel
As you know, the plane of focus is parallel to the back of the camera and stretches across the whole frame. It is parallel to the sensor in the camera, and perpendicular to the direction the lens is pointing.
I use this to my advantage by pre-focusing at a certain distance to create my plane of focus. I then having my subject move across the frame at that distance and in line with the plane of focus.
As long as they’re not getting any closer or further than where I focused, all of the shots should be sharp.
10. Use a Focus Target
Since cameras like to focus on contrast, use a focus target if you’re pre-focusing.
You have to make sure that the target is placed right against the body of the subject you’re shooting. This is so the plane of focus is set for where you want to capture them. It doesn’t have to be anything fancy. I just put some black gaffers tape on a piece of A4 size white foam-core and carry it in my bag.
Here’s what the pattern looks like (mine is too ragged to show here!):
In a pinch, I’ll even grab a white piece of paper and a black marker and draw that pattern.
None of these things will work miracles right away; in fact, some of these changes might lead to worse results at first.
Practice is the best way to master autofocus for your photographic approach with your specific camera. I’m still learning myself, delving into the different autofocus presets and custom settings on my 1DX2.
In time, you’ll master autofocus and give yourself the best chance to get sharp photos.
About the author: Matt Korinek is a commercial fitness, lifestyle, and editorial photographer currently based in Melbourne Australia. You can find more of his work and words on his website and blog, or by following him on Facebook and Instagram. This post was also published here.