The new 61-point, High Density Reticular AF system used in both the EOS 5D Mark III and the EOS-1D X allows tremendous flexibility and control, and ability to set it up to capture nearly any type of subject matter. One of the biggest advantages this wide-area AF system provides is the ability to use more than one single AF point at a time. And, this can be done in a multitude of ways.
We've discussed AF Area Selection settings in a separate article for the EOS-1D X here on the Canon Digital Learning Center; the options for the new EOS 5D Mark III are the same. But we'd like to explore the possibilities in a more application-based way, and hopefully simplify the options and where they can be utilized to their fullest. There will certainly be times where using a single AF point will deliver the optimum focus results in a given situation. But by understanding how to exploit the advantages of a true Area AF system, users will be to adjust to the situation, and get even better results.
Why not just use a single AF point?
With 61 available AF points, any time you're using one single AF point, you're dealing with a relatively small area of AF coverage. Even though the actual area covered by an AF point does extend beyond the area you see in the viewfinder, it remains a very small portion of the entire focus screen – and with many subjects, a small part of the subject you're trying to focus upon. Sometimes, this is fine. Especially with a stationary subject, when you want to get precise sharp focus on one small part of a subject or scene, using a single, manually-selected AF point is often the way to go. And for users who want to take this to the next level, you can choose Spot AF, which further reduces the size of an AF point, allowing focus on an even more precisely-chosen part of a scene.
Precise focus sounds great. But in some cases, focusing on just a small part of a subject can be a problem, or lead to focus errors and soft pictures.
Even with an AF system as advanced as that in the EOS 5D Mark III and EOS-1D X, the system still demands that the active AF point(s) see some detail or texture at the subject in order to be able to assess focus properly. This is vital: if using a single AF point, and that point falls upon a part of a subject that doesn't have much of detail, texture or contrast, it's entirely possible for the AF system to either hunt back and forth (if it's set to One-Shot AF mode), or to allow soft frames to sneak into a sequence of shots in AI Servo AF. This may not be a problem when shooting a finely-detailed, non-moving subject. But it can become a significant issue when photographing anything that's moving – it can sometimes be hard to keep the active AF point on the subject itself, let alone to keep it steadily on a detailed area of that subject.
The sample here is very typical: with little detail in the young man's shirt, the AF system is forced to look at a small area of his mid-section for folds in the shirt, texture and so on to try to ascertain sharp focus. Not always easy – and the problem is compounded if the subject is moving!
When more than one AF point becomes active, the AF system suddenly can look around for extra help whenever it needs it.
AF Point Expansion – the pro's first option
Many serious enthusiasts and professionals are used to manually selecting one AF point and working exclusively with that. Nothing wrong with this approach, although as just mentioned, you need to find a way to have the active AF point see real detail at the subject for best results.
One way is to move off-center, and manually select an AF point that's going to fall more upon a detailed part of the subject. The obvious example is to move it upward toward the face of a human subject, and this is often a good strategy.
But another option is to expand the size of the active AF point area. The 61-point AF system in the EOS 5D Mark III and EOS-1D X is especially well-suited for this, and the first method is via AF Point Expansion. This process calls upon the shooter to manually select an AF point, but the point is now surrounded by either four or eight additional "assist points". Using this AF Area selection type, the photographer initially focuses using the central, principal AF point that he or she has selected – the "larger box" of the ones visible in the finder, and in the accompanying illustrations here. But with surrounding AF points also active an on stand-by, if the principal AF point either loses track of the subject, or encounters an area without sufficient contrast and detail, one or more of the surrounding AF points immediately become active and will continue to read and track the subject.
With AF Point Expansion active, it's important to remember that the AF system still expects to perform most AF tasks using a single AF point – that is, the principal point the user has manually selected (again, it's indicated on-screen with the larger, central AF point visible, surrounded by smaller AF point icons). The remaining points in the expanded area are usually waiting to be called into action, but only if the principal point has trouble continuing to track or find the subject you're shooting.
Expanding the size of an AF point can also be useful when tracking relatively small objects (an obvious example is birds in flight), where it may be very difficult to keep one AF point continuously upon the subject. With a larger "cluster" of active points, if the subject suddenly leaves the principal AF point, the surrounding points instantly kick-in to try to locate and continue to hold focus on that subject.
Controlling how quickly the system changes AF points
There's a built-in algorithm in the AF system that's designed to smoothly move AF points from one to the next when multiple AF points are active. But in an example like the figure skaters illustrated here, it may be prudent to speed-up the system's responsiveness. That can be easily done in the AF menu, in a couple of different ways:
- Using the AF Configuration Tool (first AF menu), select either Case 5 or Case 6. The difference is that Case 5 presumes a subject like the figure skaters, who aren't rapidly moving toward or away from the camera. Case 6 would be preferable for something like a bird in flight, that's both hard to keep upon one AF point, and that that's moving at a high rate of speed, too.
- Using the same Menu screen (with any of the six AF Cases active), refine the AF pt. auto switching setting. Press the RATE button to access the Detail Settings, and scroll to AF pt. auto switching. Moving this setting from "0" towards the "2" setting increases the speed and responsiveness the system will apply when it needs to change AF points. Keep in mind: the "0" setting is intended to be optimal for most everyday uses; simply changing it to level 1 or 2 just because they're "faster" may make the AF system seem more nervous during ordinary shooting.
Zone AF – keep sharpness on the nearest subject
Another AF Area option in the EOS-1D X and EOS 5D Mark III is Zone AF. First seen in the EOS 7D, it's been refined in the 61-point AF system to allow the user to pick any of nine possible locations within the AF array. So it certainly doesn't have to be used in the center area only! Depending on the location you select, either 9 or 12 points are active in each zone (it's not possible to increase or decrease the size of a given zone, other than to change its location).
With Zone AF, you're using an active cluster of AF points where all the points are active and ready to go. Whether you're using One-Shot AF or tracking a moving subject with AI Servo AF, the Zone AF option always seeks to focus upon the nearest subject visible within the active zone of AF points. It can be ideal when you have more than one subject – especially if they're moving – and you want to insure that the nearest one to the camera is the one that's held in sharpest focus. And even when you have only one subject, Zone AF makes it a lot easier to keep it within the AF system's field of view, and insure at the same time that the nearest part of the subject is what will be focused upon. While it's true that the most critical of professional bird shooters, for example, might prefer to keep a single AF point upon the eye of a flying bird, the difficulty of this technique with a bird in flight makes Zone AF a welcome alternative for many photographers.
The point or points within the zone that correspond to that nearest subject (or nearest part of a subject) are the ones that will be used; when in AI Servo AF and tracking a moving subject, the points will continuously be updating their information, and active points within the zone will change as needed. Normally, you'll see this happening in the viewfinder, but if you find it annoying, it can be hidden from view (5th AF menu screen > AF point display during focus).
Again, Canon's new 61-point AF system allows the user to tailor just how quickly these changes of active AF point occur during a shooting sequence. The AF pt. auto switching option (see above) can be used to either speed-up or slow-down the system's tendency to change which AF points within the Zone you've chosen will be used to keep focus on the nearest subject in a scene.
Zone AF isn't for every situation. The main thing to remember is its goal of keeping the sharpest plane of focus upon the nearest thing within the zone of active AF points. Even with something as ordinary as a speaker at a podium, for instance, Zone AF might well try to put sharpest focus on the podium, rather than the speaker's face, if it's used without care. But applied in the right conditions, Zone AF can be a terrific option when you feel the need to move beyond a single AF point.
Automatic AF point selection – use the entire 61-point AF area
From time to time, even the most critical EOS shooters may want to consider this AF Area setting, when simply pin-pointing focus with a single AF point isn't right option for a given situation. It's not new to the EOS 5D Mark III or EOS-1D X... Automatic AF point selection has been in the EOS system, in one way or another, for more than two decades. But with the power of the new 61-point AF system, and recent improvements in how it works when in AI Servo AF, it's worth re-visiting.
The first thing to make clear is that Automatic AF point selection is not the same as Zone AF or AF Point Expansion. Those AF Area settings rely on restricting AF operation to a limited area of the 61-point AF array. You can move that area up and down, and/or left and right, but it's a limited area for focus (albeit larger than a single AF point). But with Automatic AF point selection, the entire 61-point area becomes potentially available for focus.
The next thing is that unlike AF Point Expansion or Zone AF, Automatic AF point selection works differently depending upon whether you're in One-Shot AF mode (locking focus on non-moving subjects) or using AI Servo AF to focus-track a moving subject.
One-Shot AF mode:
Camera focuses upon the nearest subject taken-in by the 61-point AF array; the point or points that are used to actually focus on that nearest subject will be highlighted in the viewfinder momentarily, so the shooter knows what the camera has decided upon. (This behavior is essentially identical to all previous EOS models when Automatic AF point selection is combined with One-Shot AF.)
AI Servo AF mode:
Photographer selects any ONE AF point to begin focus-tracking a moving subject; if subject then moves away from that first point, any of the remaining 60 AF points are called-in to find and continue to track its movement. Unlike either Zone AF or Automatic AF point selection with One-Shot AF active, this combination of settings won't simply try to focus on the nearest subject – once it's identified a main subject, it attempts to stick with it.
With most previous EOS cameras, Auto point selection with AI Servo required the user to start focus-tracking a moving subject initially with only the center AF point. The new EOS 5D Mark III, EOS-1D X and EOS 7D allow the user to manually pre-select any available AF point, and use this as the starting point to begin tracking a subject.
Automatic AF point selection is often looked down upon by critical, experienced shooters, who often prefer to be in direct control of where their cameras focus. But from time to time, it can be a real asset and time-saver. Refinements to the EOS 5D Mark III (and EOS-1D X) make it even more worthwhile to think about for use with solo moving subjects and AI Servo AF.
In One-Shot AF mode, Automatic AF point selection can be perfectly viable for run-and-gun candid shooting at events, where you typically are trying to focus on the nearest subject and want to insure no inadvertent focus is set on the background. When you're working quickly, it can also be useful when you know you'll be shooting fairly close to a primary subject (that you want to focus upon), but want to include a lot of background info in the shot... think of on-location fashion shots with a model, taken from fairly close with a wide-angle or standard lens, with the model positioned well off-center.
In AI Servo AF, the new system will be very useful to try in situations where a moving subject is expected to move across the frame, and composition is as important as sharp focus. In other words, anyone can simply use the center AF point and move the camera to keep a moving subject sharp as it moves side-to side across the frame, but each shot will have pretty similar composition. With the ability to pre-set an active AF starting point, and let the camera take care of shifting AF points as the subject moves away from the first point, users can maintain better composition with a sequence of shots, and often still maintain good, sharp focus... even with long telephoto lenses.
One important difference between the EOS 5D Mark III and the EOS-1D X: while both share the same 61-point AF system and essentially the same AF optics and supporting electronics, only the EOS-1D X has the 100,000 pixel RGB metering system, and ability to activate "EOS iTR" – Intelligent Tracking and Recognition. This system uses not only AF information, but information about an initial subject's color, size and location (from the RGB metering sensor) to help guide the AF system to continually update AF points when Automatic AF point selection is combined with AI Servo AF. With the EOS 5D Mark III, this automatic switching of points to follow a moving subject is done strictly using info from the AF system, not the metering system as well.
AF Point Expansion. Zone AF. Automatic AF point selection.
All are valid and valuable tools to have when pin-pointing focus with a single focus point may not be the best route to take. We've seen these options in the EOS 7D, with its 19-point AF system, but the new 61-point AF used in the EOS 5D Mark III and EOS-1D X underscores the power of using more than a single AF point.
The first key is understanding how each operates – since they're not identical – and then being able to apply their respective benefits to the type of shooting and types of subjects you're likely to encounter. These aren't necessary AF Area settings you'll use every day, all the time (although some shooters may do just that). But they are very valuable assets you can turn to when conditions call for it.
There's no such thing as one AF setting that will be perfect for every situation, but the beauty of the new Canon High Density Reticular AF system is the flexibility and options it offers to the working photographer, along with its blistering performance when shooting rapidly-moving subjects. We've outlined some examples of how multiple AF points can be applied to get better results, but most shooters will be able to come up with their own scenarios where it may be helpful to them.
Maybe the most important key point is understanding why using a single AF point and acquiring focus upon a small area of a subject or scene can sometimes be a risky proposition. Knowing how important detail, texture and contrast are to an AF sensor, it begins to make a lot more sense to occasionally open up the Canon tool box and at the very least experiment with using multiple AF points.