Canon 5D Mark III: Superior Auto Focus

Introduction
This is one of those articles I’ve been looking forward to, and dreading, at the same time. I knew going into this one, that it would be a somewhat technical article at times. There’s also a lot of ground to cover on top of that. I’m going to try to keep the technical details from getting too overwhelming, and stick to the basics. At the same time I hope to bring to light enough of the power of this aspect of the 5D Mark III, that you can see what it’s capable of.

The Auto Focus system in the 5D Mark III is a huge step forward from the previous iterations of the 5D series of cameras. Gone are the hit or miss focusing in low light, and the poor performance for fast action. Aside from a few minor differences, this is the same system found in Canon’s flagship camera, the 1Dx. What this does is to provide the owner with high end camera features, at roughly half the cost of a 1Dx. This makes it one heck of a bargain when you start comparing. Sure the 5D Mark III isn’t cheap either, but when you start to notice you have nearly everything the 1Dx offers, and a slightly high pixel count on top of it, the value really starts to become apparent when you stack it against the price tag of the 1Dx.

Focus Points

The heart of the Canon 5D Mark III’s AF (Auto-Focus) is the 61 available focus points. Tightly packed around the center of the imaging frame, these points are selectable in several configurations. 41 of these points are high precision cross type points, and these points provide even more accuracy with lenses up to f/4. These cross type points improve accuracy for still photography, as well as predictive focusing when shooting fast action. The latter is territory that was previously considered the domain of the 1D-series of full frame cameras. It should be noted that with some lenses, with a minimum aperture higher than f/4, the number of available focus points may be less. For more information about how lens selection affects available focus points, see page 79 of your owner’s manual.

Focus Modes/AF Area

You have several options at your disposal for choosing how many focus points you wish to use. The first of these options is the tried and true Single-Point mode, allowing you to choose a single focus point out of the points available to you. There is also a similar option called Single-Point Spot mode, which is the same as Single-Point except is covers an even smaller area than Single-Point.

Single-Point Spot will work best in situations that the focus point is extremely small, such as when you are shooting through a fence or similar obstruction, or focusing on a small point a detail a good distance away. In those cases, the larger single point might not be quite small enough. Both of those options are very useful when using a very narrow depth of field, as multiple focus points may have problems deciding exactly what you actually want in focus. The focus system is very accurate, but it doesn’t read minds.

Other options include AF Point Expansion, AF Point Expansion with Surrounding Points, and Zone. The two AF Point Expansion options are similar with the former starting with a single point and then using the focus points above, below, left, and right of the center point. Think of a “+” sign made out of focus points. AF Point Expansion with Surrounding Points again uses a single point to start with, but also picks all of the other points that immediately surround it. This ends up as a 3x3 grid of focus points. Zone AF builds even further upon this, giving you a block of focus points that is 4 points wide and 3 points tall.

The last option is Automatic Selection mode, which surveys all the available focus points, and uses the ones it deems necessary for what it thinks you are phtographing. In all modes except for Automatic Selection, you can move your set of focus points to any of the available points. This is obviously useful, as what you want to focus on isn’t always going to be in the same place in the viewfinder. Think of the differences when shooting between landscape and portrait modes as an example.

Canon is pretty smart when it comes to setting the focus points and zones. They knew when they set this system up that you may want to use differing points depending upon whether the camera is in portrait or landscape mode. So by using Orientation Linked AF Point (AF Tab Section 4), you can control how the 5D Mark III handles being oriented in different ways. If you frequently flip back and forth, this can be a very useful setting. I change this setting depending upon what I’m shooting.

The default method of changing the AF Area is to look through the viewfinder and continue to tap the M-Fn button until you arrive at the mode you wish to use. I have enabled Area Selection Method on the fourth panel of the menu’s AF tab, so that I can use the Main Dial. This allows me to tap the M-Fn button once, and the scroll the Main Dial to switch to the AF mode I wish to use. This is much more intuitive to me, as opposed to continually tapping the M-Fn button repeatedly.  In addition, I also employ Select AF Area Selection Mode and disable the AF Area modes I don’t normally use. This way I don’t have to scroll past them. Typically I only disable the selection of Auto-Selection, as I have yet to use it as an option. You’ll find the ability to set this option in the fourth group of the AF tab.

To manually select the AF point, or zone, you press the upper-right hand button on the back of the 5D Mark III to place the camera in the manual selection mode. Then you use the Main Dial to move the point, or zone, left or right, and the Main Dial to move it up or down. You can also use the Multi-Controller, which I find is much easier than the former method. Note than on the fifth group of the AF tab, you are provided an option for the selection pattern. This controls whether the point selection stops at the edge of the AF area or wraps back around to the other side.

AF Subject Tracking Cases

Now that I’ve covered the basics of focus points, let’s step through the 5 sections of the AF menu, and hit on what we haven’t touched. The first of these menus is a list of predefined settings that you can choose from when shooting various forms of action. I‘m using predefined loosely here, because you can actually tailor each of these to suit your needs better if you find the need to fine tune. These options are numbered from Case 1 to Case 6, and they are set up for the following purposes:

• Case 1: Versatile multipurpose
• Case 2: Continue to track subjects, ignoring possible obstacles
• Case 3: Instantly focus on subjects suddenly entering AF points
• Case 4: For subjects that accelerate or decelerate quickly
• Case 5: For erratic subjects, that move in any direction
• Case 6: For subjects that change speed and move erratically

What you’ll want to do is to match what you’re shooting with the case example that best matches your subject matter. Case 1, 4, 5, and 6, are fairly self-explanatory. However, you may be a little confused with what Case 2 and 3 are. It has to do with objects that come between you and the subject you are tracking. Just remember that Case 2 will try and ignore the object that came between you, while Case 3 will begin to instantly focus on the object that came in between you and the original subject. So it’s a matter of following the original subject, or setting focus on the new one.

As an example let’s use the example of receiver running a football down the field for a touchdown. As they pass a defensive player that is closer to the camera. The receiver is obscured briefly when the defensive player comes between you and the receiver briefly. If you are using Case 2, the focus should not lock onto the player in between you and the receiver, unless you start actively tracking that defensive player.

Now let’s say you are shooting a track event, and you are focusing on the lead runner, when the second place runner passes them coming between you and the runner you had been focusing on. If you were using Case 3 Tracking, your camera would immediately start to focus on the new runner doing the passing.

All of this translates into a very versatile way to allow you to tailor the camera’s autofocus system to suit your needs. It extends to much more than sports, by the way. I’ve used this extensively for shooting photos of birds in flight. Case 2 Tracking works extremely well for this, allowing you to track the birds as they fly behind power poles or other similar obstacles. If you find that the setting doesn’t suit you exactly right, you can change the tracking parameters for each of the Cases.

If you decide to alter these settings, you have the ability to adjust three parameters:

• Tracking sensitivity
• Accel./decel. Tracking
• AF Point Auto Switching

The first option, Tracking Sensitivity, controls how responsive the camera is to objects that come between you and the subject you are currently tracking. Accel./Decel. Tracking controls the sensitivity of the camera to notice subjects that start or stop suddenly. The last option, AF Point Auto Switching, determines the camera’s sensitivity to using different AF points, out of the ones you have selected. This is helpful should you be tracking an object that may suddenly step outside of a currently locked on focus point, but can still be picked up by another of your selected focus points. It helps to remember that just because you have enabled a focus point, it’s doesn’t mean it is always being used. One of the other points may have been locked on. All of these options make the first section of the AF tab, a very important place to start when setting your focus operation.

AI Servo Priority

For the second group of settings on the AF tab, you’ll find two lone options. These are the AI Servo image priority parameters. I told you this camera is perfect for shooting action, and this is another example of why. When in AI Servo mode, as you should be when shooting action, you can set what is most important for the camera to consider before taking the shot. The first image priority options are Release, Focus, or Equal Priority. So you get to choose which is more important, taking the shot or nailing the focus. After the first shot, you have a second set of parameters that come into play. These are the AI Servo second image priority options. The choices for this is Speed, Focus, or Equal Priority, which allows you to tailor the subsequent shots to keeping the burst rate high, or getting a good focus for each shot. As with the first option, you can also set an equal priority between the two.

One-Shot Priority 

Just so you know that One-Shot AF isn’t left out, I’ll mention that on the third section of the AF tab, you’ll find an option that tailors the One-Shot AF mode between Release and Focus. Other items on the third group for the AF tab, allow you to turn the AF-Assist flash on and off, for low light shooting, and whether to use the electronic focusing ring on lenses that have one.

AF4 Menu Items

Next we’ll move on to section 4 of the AF tab, and the first item controls what happens when the camera doesn’t gain focus. It’s called Lens Drive When AF Impossible. You can have the camera quit trying to focus, or continue to hunt for focus. I leave this set to On, which will allow it to continue to try and focus. This way as I’m moving the camera around when in AI Servo mode, it may lock focus as I’m tracking an object. If you have a very long telephoto lens, you may prefer to set this to off, as longer telephotos can become extremely out of focus if they are hunting too long. That would make gaining focus take even longer the next time around. I’ve had that happen a few times with my 400mm and 1.4x Extender, but not enough to make me switch this to off yet.

The next option allows you to alter the number of available AF points. You can choose between all 61 points, only the cross-type points, 15 points, or 9 points. This affects all AF Modes except Automatic AF Mode, which still uses all of the AF points. I leave all of the AF points available to the camera, but of the available options I could see restricting the camera to use only cross-type points due to their greater accuracy.

The last three options I’ve already mentioned earlier. The first is Select AF Area Selection Mode. It allows you to disable certain AF Area Modes. Then there’s AF Area Selection Method, which changes between multiple presses of the M-Fn button and a combination of the M-Fn button and the Main Dial to change the AF Area Mode. The last option sets whether you want separate points to be used for portrait and landscape modes.

AF5 Menu Items

On the last section of the AF tab, you find four options. The first one I’ve already mentioned as well. It is called Manual AF Point Selection Pattern, and controls whether the manual selection of points, or zones, stops at the edge of the AF points or scrolls through to the other side.

The next option is named AF Point Display During Focus. This setting controls when the focus point is shown in the viewfinder. You have options as follows:

• Constantly display focus points
• When selecting the AF point(s)
• When the camera is ready to shoot (before AF)
• During AF operation
• When focus is achieved

In addition, you can also control when the focus points will illuminate in red, as opposed to the standard black. You can choose between:

• Auto: AF Points and grid automatically illuminate in red under low light
• On: AF Points and grid always illuminate in red
• Off: AF Points and grid never illuminate in red

The last option allows you to micro adjust your lenses focusing operation. This allows you to fine tune your lenses individually, providing extremely precise focusing capabilities. For most people this is not necessary, although it is available for those that what to go the extra distance to get exacting results. Make sure you have a firm understanding of micro adjustment before you attempt this. If you don’t know what you are doing, you could end up having your lens focusing worse, not better.

Other AF Items To Consider

We’ve covered the menu, but there are a few more things to cover regarding the AF system in general. First is the AF Mode. You have three options:

• One Shot: For still subjects
• AI Servo: For moving subjects
• AI Focus: Switches from One Shot to AI Servo if the subject starts moving

I do all of my shooting in either One-Shot or AI Servo modes. While the 5D Mark III may be better in AI Focus mode than its predecessors, I have been trained to think in those two modes only. AI Focus just hasn’t worked well for me in the past, so I avoid it. It’s not like AI Servo won’t focus on a still object anyway, and the only reason it would lose focus would be if you move the camera off of the target yourself.

A Couple of AF Tips and Customization Options

One thing I typically do, to help switch modes quickly if needed, is to enlist the help of my DOF (Depth Of Field) preview button. Most of the time it is set so that it switches between One-Shot and AI Servo when pressed. This way I have instant access to the other mode if it is quickly needed. You’ll find this option under the Custom Functions mention in my Canon 5D Mark III:  Menu Basics and Highlights, Part 3 article.

One last helpful item I want to cover briefly is registered AF points and zones. Should you want quick access to a certain AF point or zone, you can register that to a camera button as well. The couple of times I’ve used this, I’ve assigned a registered point to the DOF preview button that I just mentioned. You’ll do this through the Custom Functions as well, and it will take the place of the One-Shot/AI Servo toggle I just mentioned if you decide to use it. Once you set it in Custom Functions, select the AF points, or zone, you wish to select. Then press the ISO and AF point button (upper righthand button on the back of the camera) together until you hear a beep. Now whenever you hit your DOF preview button, you’ll be set back instantly to your registered AF point setting.

My Experiences

There’s been a lot of information that has been discussed here, and I know I’ve only given you a brief walkthrough. However the best way to learn is to get out there and start shooting with your camera. I practice that mantra, and rest assured after shooting plenty of action in the form of soccer games and wildlife, I am seriously impressed with how well this camera performs when it comes catching the action. My rate of keeper images has jumped dramatically, leaving me to choose between the shots I like the most, not shots of varying degrees of focus.

The 5D Mark III has impressed me, especially with how well it can ignore those obstacles that briefly come between you and your subject. This was very important for wildlife, but it was especially so for when I photographed a local soccer game. Even with players constantly running between me and my subject, the 5D Mark III did an excellent job of maintaining the task of following the subject.

In addition, tough lighting and contrast conditions haven’t seemed to phase the 5D Mark III either. While at Carolina Beach a few weeks ago, I took some photos of jellyfish. The dark water and low contrast of the jellyfish didn’t trip up the AF system one bit. Also one should note, that the sample photo provided is at 25,600 ISO!

Outside in the sun and sand, I knew the lighting was more than adequate, but I found tracking the coastal pelicans an easy task. This was even true when using my 400mm f/5.6 and 1.4x III Extender combo. This forced me to shoot at an aperture of f/8, which gives me only the center AF point to use instead of multiple focus points. It’s nice to know that a single AF point can still track extremely well.

The AF capabilities found in the 5D Mark III are so much better than the 5D Mark II’s I’ve played with. While the image quality from the 5D Mark II was incredible, if it had a fault, is was the AF system in general. This was especially true under low light. Canon has cured this perfectly, by using this incredibly capable AF system. The ability to catch action is simply one of the strongest points of this camera, so experiment with it and don’t be afraid to exploit its capabilities. That’s what it is there for.

I know I plan to give the 5D Mark III one heck of a workout in just a few weeks at Mustang Week in Myrtle Beach. While they’ll be car shows that any camera could easily catch, I’ll also be there at some of the more action packed events trying my hand at panning and stopping the action. Practice makes perfect, and I plan to get as much practice as I can!