Understanding EOS Autofocus: The EOS 5D Mark III and EOS 1D-X

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EOS 5D Mark III AF points

If you look around online about the EOS 5D Mark II* you will inevitably come across negative comments about its autofocus performance. Is that justified? Well, partially (in my opinion). I see no good reason why the EOS 5D Mark II has only one cross-type AF point when the EOS 40D (released earlier) and EOS 50D (released at the same time) have nine cross-type AF points.

* I looked at the autofocus (AF) performance of my EOS 5D Mark II (plus other EOS cameras with the same nine point AF array) earlier in the series. You can read that article here.

Thankfully, any autofocus concerns with the 5D cameras have been well and truly put to rest with the release of the EOS 5D Mark III. It has 41 cross-type AF points and features the same autofocus system as the top-of-the-line EOS 1D-X. Together, these two cameras contain Canon’s most advanced autofocus system yet.

While there are some minor differences, the autofocus of the EOS 5D Mark III and 1D-X is nearly identical, so I will look at both together in this article.


The EOS 5D Mark III has a 61 point AF array with up to 41 cross-type AF sensors available (depending on the maximum aperture of the lens mounted on the camera). This is more AF points than any other EOS camera except the 1D-X.

This diagram shows the arrangement of the 61 AF points:

EOS 5D MK III AF point array

If you have a lens with a maximum aperture of f5.6 on the camera (with some exceptions) you have 21 cross-type AF points available (marked in red):

EOS 5D Mk III cross-type AF points

If you have a lens with a maximum aperture of f4 or wider on the camera you have an extra 20 cross-type AF points available (marked in green):

EOS 5D Mk III cross-type AF points

If you have a lens with a maximum aperture of f2.8 or wider on the camera the five centre AF points become high precision points with twice the sensitivity of the rest to assist with focusing prime lenses at wide apertures (marked in red):

EOS 5D Mk III high-precision AF points

If you use the camera in Single point AF or Spot AF modes and select an AF point that is not a cross-type point, the AF point blinks in the viewfinder to let you know. I like this – it’s very useful as it means that you don’t have to memorise the above patterns.

This is how the autofocus point array of the EOS 5D Mark III compares to those of the EOS 5D Mark II and EOS 7D. As well as having more autofocus points, they cover a larger area of the viewfinder:

EOS AF point comparison

The EOS 5D Mark III (and 1D-X) use a transparent LCD overlay in the viewfinder to give more flexibility in the way the autofocus points are displayed and used (the only other EOS camera with a transparent LCD overlay in the viewfinder is the 7D). This camera menu screen shot from the 5D Mark III shows you the options. Choose anything other than 61 points and the camera displays only the available AF points in the viewfinder. Clever!

EOS 5D Mk III menu

Note that you lose some of the above functionality with certain zoom lenses (those with maximum apertures approaching f5.6, such as an EF 28-80mm f3.5-5.6 lens), or if you use a prime lens with the 1.4x or 2x extenders. Canon lists all the affected lenses in the instruction manual.

Autofocus tracking

Autofocus has two purposes. One is to be accurate when focusing on a still subject (ie when the camera is in One Shot AF mode). The other is to accurately track and focus on a moving subject in AI Servo mode. The autofocus system of the EOS 5D Mark III has several features that help achieve the second purpose.

Part of that is down to the 61 point AF array. This is great for shooting still subjects, but helps the camera keep track of moving subjects as well.

Another feature is that the camera’s predictive autofocus is highly customisable. You can calibrate it to suit the type of moving subject you are photographing.

There are six ‘cases’, and you simply choose the one that you want to use. This is what they do, in brief:

Case 1: Versatile multi purpose setting

This is a general setting that you will use, unless one of the other cases suits your subject better.

Case 2: Continue to track subject, ignoring possible obstacles

The camera locks onto the moving subject and tries not to be influenced by anything that appears between your lens and the subject, or to focus on the background if the subject leaves the area of the viewfinder covered by the AF points.

Example use: You could use this if you were photographing a rugby player in a scrum and wanted the camera to keep focus on that player, and not any others that are closer.

Case 3: Instantly focus on subjects suddenly entering AF points

This does the opposite to the previous case. If a new subject enters the area of the viewfinder covered by the AF points, the camera will stop tracking the current subject and switch to the new one.

Example use: This is useful for photographing sports or wildlife where you want the camera to focus on whatever player or animal is closest to the camera.

Case 4: For subjects that accelerate or decelerate quickly

Some subjects move around at an even speed (such as a bird in flight) and others may change speed or direction quickly (such as players on a sports field). This mode lets the camera know that the subject may change direction and speed rapidly. It lets the camera know how you expect the subject to behave so that it can use the information to keep track better.

Example use: Cornering in motor sports, football players avoiding tackles.

Case 5: For erratic subjects moving quickly in any direction

This mode tells the camera that the subject may move quickly in any direction and change direction at any moment. Helps the camera keep track.

Example use: Figure skating, air races.

Case 6: For subjects that change speed and move erratically.

This case combines the two types of movement of the previous two cases.

Example use: Basketball or rhythmic gymnastics.

Note: Cases five and six can’t be used in Single point AF or Single point spot AF modes. They are designed to be used with multiple AF points to track the subject.

Furthermore, each of these cases has parameters that you can adjust to tweak the camera’s autofocus to work the way you want it to.

The menu options are well thought out and make a complex and potentially confusing autofocus system relatively simple to use.


The autofocus system used in the EOS 5D Mark III first appeared in the EOS 1D-X. The two systems are nearly identical but the 1D-X does have a slight edge when it comes to tracking moving subjects.

This is very clever – the camera uses the data gathered by its autoexposure sensor to calculate the colour of the moving subject that it supposed to track. It then uses this information to help differentiate the subject from the background. It works with faces as well as colour.

The EOS 5D Mark III has a different autoexposure sensor and doesn’t support this feature.


Canon have answered any complaints about the autofocus performance of the EOS 5D Mark II emphatically in the EOS 5D Mark III. This camera really does seem to have everything – high ISO performance, a full-frame sensor and high-precision autofocus.

If you’re a sports or wildlife photographer, or simply want to have a camera with high-performance autofocus, then there are now three superb cameras to choose from: the EOS 7D, 5D Mark III and 1D-X. I await the anticipated release of a 7D Mark II this year with interest.

Further reading

These articles will give you more information about the Canon EOS system. My EOS autofocus series goes into the autofocus systems of some of the above cameras in much more detail:

My detailed review of the EOS 5D Mark III

Canon Speedlite Buyer’s Guide – You’ve bought a new EOS camera, now you want to buy a flash unit to go with it. This article explores the current range of Canon Speedlite units.

EOS Autofocus series

Understanding EOS Autofocus: The EOS 70D

Understanding EOS Autofocus: The EOS 1D Mark IV

Understanding EOS Autofocus: The EOS 5D Mark III and EOS 1D X

Understanding EOS Autofocus: The EOS 7D

Understanding EOS

Understanding EOS ebook

 My ebook Understanding EOS is the perfect guide for anybody who wants to learn how to get the best out of their EOS camera. Click the link to learn more, and see the other ebooks in the Understanding EOS series.


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2 Responses to “Understanding EOS Autofocus: The EOS 5D Mark III and EOS 1D-X”

  1. DaveFisher says:

    Sounds great but my 5d mkIII doesn’t hang-on to to gulls in flight in AI servo, consequently I get in-focus sea and out-of-focus gulls, forcing me to reduce to single-point AF (all while using 100-400 L lens).

  2. Tom Reese says:

    I’m not nearly as happy with my 5DMIII focusing as you are. I’ve been setting up near bird feeders trying to catch them in flight (using a wireless remote) and the camera continually ignores the birds and focuses on the background. The birds show in the frames as OOF smears so I’m not missing them.

    If I had one photographic wish it would be for a focus limit switch on the lens that ranged from minimum to 1/3 of the range.

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