Rudy Winston
Rudy Winston

Rudy Winston has over 16 years experience with Canon USA's Pro Products team, and has been responsible during that time for training Canon's staff on new products, creating presentations for customers and dealers, numerous writing projects, and providing technical assistance to professional and amateur photographers.

EOS-1D X: AF point selection using color information

September 09, 2013

A new EOS feature in the Canon EOS-1D X is its ability to use its 100,000 pixel RGB metering system to actually assist the AF system in focusing upon a subject. The camera can automatically change AF points on the fly to follow a subject as it moves around the picture area, and this option connects it to the color metering system. Using the subject’s color, the camera can continually update and put new AF points on the subject to keep it in focus. We’ll explore this feature in this article and give ideas of how and when it may be useful.

The basics of Automatic AF point selection

The ability to have the camera automatically select one or more AF points is nothing new in Canon EOS cameras, as it’s been with us since the 1990s. Any time we’ve had more than one single AF point in the camera, EOS cameras have offered Automatic AF point selection (the option to have all points active and let the camera automatically choose which AF point to use for a given subject). Here’s how it works:

  • One-Shot AF mode: With stationary subjects, the camera reads the scene with all AF points active and the point or points that see the nearest subject with detail are selected and used to focus. Those points are highlighted briefly in the viewfinder, so the shooter knows where and what the camera has decided to focus upon.
  • AI Servo AF mode: When tracking moving subjects with AI Servo AF, automatic AF point selection historically has required starting to follow the subject with the center AF point. Once the AF system has begun to track its movement, the surrounding AF points would be used to continue to focus upon it, if the subject moved away from the center AF point.

A new option was launched with the EOS 7D, and continues on the EOS-1D X, EOS 5D Mark III and EOS 70D: when set for AI Servo AF and Automatic AF point selection is active, the user is asked to manually select a single starting point for AF. With these cameras, the system no longer has to start using the center AF point. If a subject was anticipated to move, for instance, right to left across the frame, a user could pick the far right side AF point, start focus tracking with it, and allow the subject to move across the frame. Once it begins to move away from that first pre-selected AF point on the right side, other AF points will become active and continue to focus-track this subject, not just right to left, but toward or away from the camera. As long as the AF system has sufficient light and detail at the subject, it will continue to maintain focus on the subject, as long as it stays within the area covered by AF points.

Regardless, the sole criteria up to now for Automatic AF point selection with AI Servo AF has been information from the AF points and the AF sensor.

Big news with the EOS-1D X: 100,000 pixel RGB metering

This is the first Canon EOS camera ever to be able to meter not only light values, but also to detect subject color using an actual RGB sensor — a smaller, reduced resolution version of the imaging sensor in a modern digital SLR. While this new metering sensor is used to fine-tune exposure metering, Canon’s engineers realized that its ability to recognize subjects could be used in other important ways too.

With over 100,000 pixels on this RGB metering sensor, the system can read sufficient detail of a scene to begin to identify subjects with a fairly high degree of resolution and accuracy. Canon calls the metering system’s ability to do this “EOS iSA” — Intelligent Scene Analysis. Again, the metering system is reading not only brightness, but color in a scene and where that color is distributed throughout the frame.

One of the key new innovations is using color information to assist the AF system when it’s in Automatic AF point selection mode. Focus upon a subject with all the AF points active and the AF system initially focuses upon it. But behind the scenes, the RGB metering system registers the color, size and shape of the subject being initially focused upon. Armed with this info, the metering system knows not only where the subject is, but its color characteristics — in essence, what it looks like. The Intelligent Subject Analysis system has taken the first step for the photographer.

And as a subject moves around the viewfinder, the metering system continues to update its position, using color and shape to follow the subject. As it moves, the metering system “tells” the AF system where the subject is. Now, the Automatic AF point selection system can continuously change active AF points to keep the initial subject in focus as it moves around the finder. This is the genesis of Canon’s Intelligent Tracking and Recognition (iTR) feature.

EOS iTR AF: Intelligent Tracking and Recognition

This is a great new feature for anyone who anticipates shooting moving subjects, like motorsports, wildlife, birds in flight, sports, etc., to try because the potential is almost endless. Any time a photographer is likely to encounter movement across part or all of the frame and wants to keep the camera focused upon that subject, the EOS-1D X’s Intelligent Tracking and Recognition (using color information) is a tool to keep in mind.

Using it is simple:

  1. Set the EOS-1D X to the AI Servo AF mode.
  2. Be sure the camera is set to Automatic AF point selection mode (in the viewfinder, you’ll see a thin border surrounding the AF point array).
  3. Manually select any single point as the starting point for focus tracking, whether centered or off-center.
  4. Activate AF using color information in the Menu:

    4th AF menu > Auto AF pt. select criteria > EOS iTR AF

That’s it! Now, you begin to initially track a subject at the AF point you dialed in as the starting point. Press whatever button you’re using to activate AF and the camera starts to focus-track your subject. If the subject moves away from that AF point, its shape, size and color are monitored by the RGB metering system and tells the AF system which points to continuously update to keep it in sharp focus.

Face Detect AF: Keep AF points on a face, even if it moves

Remarkably, this new 100,000 pixel RGB metering system can also detect faces. The EOS-1D X is the world’s first SLR with the ability to perform Face Detection when using the standard eye-level viewfinder (all previous D-SLRs with face detection capability could only do it during Live View operation, when the camera’s actual imaging sensor was used to read the scene). Focus upon a face and, if you’re in AI Servo AF, the camera will continue to put AF points upon that face if the subject begins to move around the picture area. The RGB metering system is using a combination of skin tone, facial details and shapes to recognize the subject as a human face. And the EOS iTR AF allows this face recognition system to “talk” to the AF system. Once again, EOS iTR AF combines with Automatic AF point selection to allow the AF system to follow a primary detected face, if it moves around the frame during a sequence of pictures.

This can be useful not only for shooting portraits, but for many other types of shooting with people — wedding and event shooting, theater and stage work or even perhaps sports where athletes don’t usually wear face masks, which may interfere with face detection. Historically, a problem professionals complain about is difficulty when working with fast lenses at wide apertures in keeping the faces tack-sharp. Face Detect AF with the EOS-1D X moves the concept of face detection from something aimed at snap-shooters to a tool that the critical professional may find helpful from time to time.

Once again, if the EOS iTR AF is active in the EOS-1D X’s AF menu and the camera is set for Automatic AF point selection, this face detection technology is at your fingertips.

What are the differences, compared to the EOS 5D Mark III?

While both the EOS 5D Mark III and the top-of-the-line EOS-1D X cameras share the same 61-point, High Density Reticular AF system, only the EOS-1D X has it backed-up with the 100,000-pixel RGB metering system. So while both cameras provide incredible metering flexibility and performance — and focus-tracking in AI Servo AF with a manually-selected AF point should essentially be equal between the two — the Face Detect AF and EOS iTR technologies in the EOS-1D X can and will make a big difference in AF performance when the camera is picking the focusing point.

Summary

Up to now, many professionals have eschewed the idea of even using Automatic AF point selection, preferring most of the time to manually select a single point and use that exclusively for focusing. While that option is certainly available to the EOS-1D X user, this camera uses its focus system technology and newfound RGB metering technology to make the idea of letting the camera choose the focus point a viable option in certain situations.

The potential of the EOS-1D X’s Subject Recognition AF, whether using RGB color information to keep AF points upon any moving subject or using its Face Detect technology to keep a primary face in focus, offers at the very least some intriguing potential to the critical enthusiast and professional. Even the very finest of sports or wildlife shooters from time to time would like to shoot a sequence of a moving subject and have that subject be able to progressively move across the frame through the sequence — and know that they can continue to keep it tack-sharp even if working with a long, fast telephoto lens. Historically, Automatic AF point selection with fast moving subjects was a hit or miss proposition. The new power of the EOS-1D X’s AF system and, in particular, the EOS iTR AF system offers a real chance that for some applications, professional photographers may at last feel that this type of automation is a tool they can comfortably turn to.

The CDLC contributors are compensated spokespersons and actual users of the Canon products that they promote.

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