Take a new look at Canon's Eye Control AF

The Canon EOS R3 introduced a host of technical innovations, but one of the most talked-about of these was a refinement of a revolutionary technology from the past: Eye Control Autofocus. Originally developed 30 years ago, Eye Control AF enables the camera to set or switch the autofocus point by detecting what you're looking at in the viewfinder. In the EOS R3, the technology has been reimagined for a new generation of cameras.

It's important to bear in mind the difference between Eye Control and Eye Detection/Tracking – the two autofocus technologies work together, as we'll see, but they are distinct from each other. A number of Canon EOS DSLR and mirrorless cameras include Eye Detection and Tracking AF, enabling them to lock on to the eyes of human and animal subjects and keep them in focus, but as of mid-2022 only the EOS R3 has Eye Control AF, which monitors the photographer's eye to set or move the autofocus point.

Here, we delve into the development of Eye Control AF, speak to Canon Europe Senior Product Specialist Mike Burnhill about the innovations behind the current technology and how Canon engineers refined its accuracy, and discover how professionals such as sports photographer Łukasz Skwiot are using it to capture sharp shots of decisive moments.

The original version of Eye Control was implemented in the Canon EOS 5 in 1992, then included in a few other 35mm film SLRs and camcorders. It attracted a lot of attention, but the technology at that time was still fraught with challenges – accuracy varied from person to person, some users experienced eye strain, and slight eye movement during shooting sometimes caused the focus to shift or blur. As digital SLRs emerged and features such as multi-controllers were added to cameras, Eye Control AF technology was shelved for the time being.

"But once we got to the latest generation of mirrorless cameras, the opportunity became available to implement the technology again," explains Mike. "With mirrorless, there was a leap in technology that provided the autofocus accuracy, positioning and fluidity that was needed for Eye Control AF."

Naturally the technology behind Eye Control AF has evolved far beyond the original version. When Eye Control AF was introduced in the Canon EOS 5, a single infrared sensor was used to track the movement of the photographer's eye. But the EOS R3 system features eight infrared LEDs at different angles. "Not all of them are used simultaneously," Mike explains. "The sensors are used for different purposes, depending on things like how close your eye is or whether they detect that you're wearing glasses.

"There's also a small imaging sensor inside the viewfinder. So the infrared light shines into your eye and illuminates the back of your eyeball, and then it bounces back to this sensor, which creates a retina scan. The sensor has a direct relationship to the image on the high-resolution OLED screen in the electronic viewfinder, so it knows which area of the image the eye is looking at and which AF points this corresponds to on the main imaging sensor."

Of course, if the camera is going to focus with precision, it needs to know precisely where you're looking. That's why calibration is key when it comes to accurate Eye Control AF. With the original system there was only one calibration, but with the EOS R3's Eye Control AF it's possible to refine the calibration.

"The problem is that the shape of the human eye changes a lot," says Mike. "When you move from a dark location to a bright one, for example, or when you rotate the camera from vertical to horizontal, the eye can look very different. So one of the biggest changes in the EOS R3's version of the Eye Control AF system is its ability to rebuild its algorithm for the calibration, to refine it. So the more you do it, the better it gets."

That said, you don't have to calibrate Eye Control AF every time you pick up the camera, Mike adds. "But we recommend that when you first get the camera, you calibrate it in different ways. Use it in the different orientations that you're going to use it in and how you'd use it, indoors and outdoors, on a dull day and a sunny day, and so on."

Six distinct Eye Control AF calibrations can be saved to the camera. "If you wear glasses, the distance from your eye might be different compared to if you were wearing contact lenses, so it's worth saving separate settings," Mike suggests. "You can even save them to a memory card, so you only have to calibrate the setting in one camera and then you can load it into other bodies."

It's not just the shape of a photographer's eye in different situations that the Eye Control AF system has to accommodate. Whether it's the thickness of eyelids, length of eyelashes or other such features, no two people's eyes are the same. Glasses can further complicate matters, and even the different ways in which photographers hold their cameras mean that the distance between the eye and the camera viewfinder differs from person to person.

To address such issues, Canon recruited hundreds of testers to assess its technology under challenging conditions. Developers even went so far as to create an artificial eyeball for use in trials. Canon's medical division was also consulted.

The EOS R3's Eye Control AF doesn't require you to constantly keep your eye focused on the subject. "Eye Control AF has been designed to work alongside the camera's subject detection functionality," says Mike. "And they're the perfect combination.

"For example, say you're faced with five actors on a red carpet. Who is the most important person to focus on? Obviously the human brain is very good at recognising and identifying people, and Eye Control AF gives you an intuitive way to communicate that to the camera.

"Once the system knows which person you want to focus on, it can lock on to their eye or their face, and it can track them as they move. If you want to choose someone else, you can instruct the camera to check where you're looking, and the camera will switch focus. So it's a quick initial decision, and then you can let the camera do all of the hard, precision work for you."

Eye Control AF has obvious benefits where speed is crucial, such as news and wedding photography. Action photographer Vladimir Rys put it to the test on his first electric rally car shoot, where he found it greatly sped up the process of selecting between multiple possible subjects. He used it together with the EOS R3's groundbreaking Vehicle Tracking AF, which locked on to the subject he identified and stayed focused on it as long as he wanted.

Canon cameras support multiple AF selection methods, so you can use the touchscreen to tap the area you want to focus on, as well as move the AF point using the multi-controller. But nothing is faster and more intuitive than simply looking at the subject you want.

"When photographing sports, especially professional ones, we often have a fraction of a second for the correct focus – otherwise we will miss the decisive moment," says sports photographer Łukasz Skwiot. For him, there's "no comparison" in speed between Eye Control AF and other ways of selecting an autofocus point. "I use the Canon EOS-1D X Mark III's Smart Controller on a daily basis, and that allows me to change AF points very quickly," he says. "But it's not as fast as Eye Control AF on the EOS R3."

At a football match, Łukasz says, "all I had to do was look at the face of the football player I wanted to focus on and, with Eye Detection enabled, the camera would focus precisely on the player's eyes. Likewise, when I was photographing taekwondo – the heavily padded helmets posed no problem for the system." When he photographed two taekwondo practitioners training side-by-side, once he had selected one of them using Eye Control AF, the Eye Tracking continued to follow the selected subject even when the other person was closer to the camera and occasionally obscured the selected subject's face.

"Some people said Eye Control AF was just a marketing gimmick that will not work in practice," Łukasz concludes. "After testing it, I have a completely different opinion. This is a truly useful feature, and I love it."