What You Need to Know About eye auto focus

I have mentioned time and again about my habit to use single focus point on Canon cameras. It was a habit I have developed for 10 years or possibly longer, regardless how many focus points a DSLR camera offers. It doesn’t matter my Canon 7D has 19 focus points, and my Canon 5D MarkIII has 61 points, I always only used one focus point.

See a few history articles where I mentioned this habit, written 5-7 years ago:

7 Tips For Getting Tack Sharp Landscape Photos

10 Steps Workflow & Camera Setting For Best Landscape Photos

Night Photography - How to Start

How To Photograph babies

Other than single focus point, I also had a long habit of “First Compose Then Focus”

When I take a photo, I first compose, then manually move the single focus point onto my main subject. This is different from first focus and then recompose method. The latter might work for some occasions (when you use a large f-stop for deep depth of field), but the former focuses more accurately, particularly for shallow depth of field with small f-stop/wide aperture.

The only shortcoming of the “first compose then focus” method is: it takes more time to focus. For a moving subject, for example, a walking toddler or a running dog, using this method to nail the focus is not easy. For a fast moving subject, such as a race car, a flying bird, this method most likely won’t work. This is when I had to use Al Servo.  On a Canon camera, Al Servo allows the camera to track moving subjects and continuously focus on them.  On Nikon, the equivalent is AF-C (continuous auto focus).

Al Servo with busy foreground and background. Canon 5D MarkIII, ISO100, 105mm, f/3.5, 1/1000sec

However, I was never a big fan of Al Servo.  I used it mostly with my 70-200mm lens, shooting something outdoors with a long range of movement.  If I set my f-stop too small (to achieve the blurry background effect), or the shutter speed wasn’t fast enough, the Al Servo could be a hit or miss.  I constantly had to shoot more images than I wanted, and select among large number of photos in post processing to find those with perfect face or eye focus.

So unless I had to use Al Servo, I used single focus point for everything, no matter for people or landscape.  I split equal amount of attention on moving my focus point and getting the composition right.

All these have changed!

What is eye AF

Fast forward into 2018.

I purchased my first non Canon full frame camera - Sony A7III. It was a switch after a long agonizing wait. (See full story)

This time around, my first step to customize the camera was to set up eye autofocus, or eye AF. It is a game changer! If there’s only one reason why I purchased this camera, this is it!

eye AF for indoor low light, ISO12800, 55mm, f/1.8, 1/250sec

Eye AF allows Sony camera to not only track and continuously focus on a moving subject, but more precisely on the subject’s eyes.

The focus point is usually a dot on the eye. So technically, it is a single focus point.

eye AF with object (hand) closer to the camera, ISO640, 55mm, f/1.8, 1/250sec

Why is eye AF a game changer

Eye AF does not require me to manually move the single focus point to the eye. Instead, the camera automatically finds the eye and focuses on it. It is fast, precise, and cuts out manual mistakes.

eye AF with moving subject. ISO1600, 55mm, f/1.8, 1/320sec

By dramatically saving the time on focus, thanks also to Sony mirrorless full frame cameras’ superior low light performance (compared to traditional Canon and Nikon DSLR), I can now direct almost 100% of my attention on composition, in most light conditions, therefore increasing the overall quality of my image.

eye AF in an aquarium with low light. ISO5000, 55mm, f1.8, 1/250sec

For the first time after many years, I’m allowing my camera to decide where to focus and how to focus. Franky, it does a great job!

eye AF with fast moving subject. ISO320, 55mm, f/1.8, 1/8000sec

Caveat: Eye AF works a lot better on native Sony lenses

If you use a lens adapter to mount your Canon or Nikon lens on Sony mirrorless cameras with the eye AF function, the result might be unpredictable – ranging from slower speed of focus, inconsistent performance, to not working at all.

See following image with my Canon 16-35mm, f/2.8L ii lens mounted on Canon 7D (non-full-frame DSLR) through Sigma MC-11 adapter. The adapter was a recent acquisition after my full frame Canon 5D Mark III was destroyed in the thunderstorm. I haven’t tested it for a long time but so far the eye AF works, not exactly as fast or precise as the native lens Sony Zeiss 55mm, f/1.8 though.

eye AF with MC-11 adapter, ISO125, 21mm, f/2.8, 1/160sec

How to set up eye AF

The following uses Sony A7III as example. You should be able to set up eye AF in most recent Sony full frame mirrorless cameras.

Step 1 – make sure the camera is in continuous auto focus mode

In menu tab 1, page 5, set “Continuous AF” for Focus Mode, and “Wide” for Focus Area.

“Continuous AF” allows the camera to constantly search the subject and focus on it.  When you activate Eye AF, it continuously tracks and focuses on the eye.

“Wide”, in conjunction with the Eye AF setting, allows the camera to automatically detect and focus on the eye no matter where the eye is in your composition.

Step 2 – set custom button to trigger eye AF function

On menu tab 2, page 8, select the top “Custom Key” (see below).

Note there are 3 “custom key” here. In case you are curious, the first one is for photography custom setting, the 2nd one is for movie, and the 3rd one is for review.

As mentioned in my “one camera one lens” solution, I only use a prime lens on Sony A7III.  I don’t need to use my left hand to change the zoom, nor hold the lens (as the lens is very small).  Most of the time my left hand is idle by simply holding the camera.

I decided to use custom button 3 for Eye AF, as this is the only button located on the left side of the camera body.  It is easy to find, and won’t cause confusion or accident clicks on other buttons, which all located on the right side of the camera.

Using my left hand, or left thumb precisely, to turn on Eye AF, also frees my right hand to do other adjustments.

For example, you want to change aperture and shutter speed fast in the full manual mode.  You use your right thumb and index finger to change the dials.  You also would like to change some settings assigned to the other custom buttons (all on the right hand side of your camera), such as drive mode, focus setting, etc. (See my last post about my top 5 favorite custom settings on Sony A7III). In the mean time you want to lock the eye focus.  If your eye AF custom button is also set on the right side of the camera, typically accessed by either right thumb or index finger, you’ll end up with too many tasks on the right hand. You could lose some shots.

However, if you use a zoom lens, which is typically much larger than a prime, and will keep your left hand busy, I’d suggest you arrange your eye AF custom button on the right side of the camera. It will be awkward to adjust the zoom and press the C3 button at the same time.

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OK, looks like you have just enabled the most powerful button on your camera. Is that enough?

Not quite yet. Even if you are a wedding, children, or street photographer, and photograph people most of the time, there are situations that you can’t really benefit from Eye AF. For example:

Subject turning away from camera. ISO100, 55mm, f/1.8, 1/5000sec

• The person turns away from the camera. The camera can’t detect eyes

• You have too many people in the same shot, or there are too many eyes

• Occasionally, you want to photograph flowers, a birthday cake, landscape or anything other than a person. There’s no eye

More than one person in the shot. With face priority, eye AF doesn’t necessarily focus on the eyes closer to the camera

Now you go back to the traditional shutter half push, or monitor screen tap to focus, but you need to direct the camera where to focus and how to focus correctly.

This is when you need to adjust additional settings (see my last post Top 5 Custom Buttons To Speed Up Your Photography Workflow On Sony A7III)

In summary, if you are a parent, children, wedding photographer, or even wild life photographer, you’ll love eye AF.

How to set up your eye AF, and any other custom buttons, depends on the type of lens you use, and the frequency you change your settings. It is very personal, and could be optimized over the time. The more you get used to your camera, the more efficient your workflow becomes, and the more you could focus on your composition.

Remember, all the camera settings are just a tool to help you speed up your workflow. Eventually, it’s you, not the camera, that’s making a great image. Your composition, seen through your lens, is what I believe the most important factor that sets you apart from other photographers. (see Less Is More - 7 Approaches To Create Simple Yet Strong Composition)

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