Autofocus

Focus Module

The Canon EOS 5DS and SR use variations of the 61-point autofocus module used in the EOS-1D X and 5D Mark III. This has a class-leading 41 cross-type AF points that can fix focus on both horizontal and vertical edges, increasing the in-focus rate in challenging light conditions. This is because in challenging, low-contrast lighting (low light or backlit situations), it's simply better to have an AF sensor 'looking' along multiple axes for detail to make measurements from. 21 of the camera's central cross-type points continue to work even when paired with relatively slow lenses, remaining active with f/5.6 lenses (or lens/teleconverter combinations that give an f/5.6 maximum aperture).

A special note should be made about the 5 central AF points, shown in blue with an X below. When these points are paired with F2.8 or faster lenses, they convert to dual-cross-type, adding diagonal cross-sensitivity in addition to traditional cross-sensitivity (imagine an X overlaid on a + shape). The diagonal cross-type sensors in those 5 central points have longer baselines and therefore exhibit a high degree of focus precision when paired with fast lenses. We found incredibly high precision when paired with Canon's latest lenses, with nearly mirrorless levels of precision even at F1.4. Roger Cicala over at LensRentals hypothesizes this may be due to a feedback mechanism in newer lenses that work in combination with the high precision sensors for enhanced focus precision. You'll still have to microadjust some of your lenses for focus accuracy, but after you do, you can expect very good focus repeatability with these central AF points.

We summarize all the AF points below, where you can mouse-over a few different options to see how different lenses' maximum apertures affect line sensitivity of the various AF points:

F2.8 or brighter
F2.8–F4
F5.6 or brighter

Focus Modes

The high-res twins offer a similar set of options to other Canon models, including the ability to only use specific focus points or zones, along with single AF (One Shot), continuous AF (AI Servo) and a mode that tries to automatically switch between the two (AI Focus). This auto mode, like just about every camera we've ever tested, tends to be too slow in recognizing motion, so isn't necessarily that useful.

Choosing the AF point

The cameras offers a range of ways to select or limit the focus points that the camera will use. Working outward from finest to least specific, the options are: Spot AF, Single AF, Expand AF area +, Expand AF area Surround, Zone AF and Autoselect 61 point AF. The camera can be limited to just using cross-type or to a 15 or 9-point array, to make it faster to select a point manually.

The camera allows you to select the AF area with up to six levels of precision. In AI Servo mode, you select the initial focus point or region in all of these area modes but in single AF and 61 point area modes, the camera will choose the closest subject.

A menu option lets you disable any of these options that you don't regularly use, making it quicker to jump between the ones you do.

There are also options to define whether the camera prioritises focus or shooting speed when combining continuous AF and continuous shooting. It also provides an option to specify a different priority setting for the first shot in a burst.

Continuous AF behavior settings

The 5DS and 5DS R offer the same use-case based AF behavior presets first introduced on the 1D X, designed to take some of the confusion and

In AI Servo mode, EOS 5DS and SR have the same autofocus options that first appeared in Canon's professional sports camera: the 1D X. These take the existing three settings for how tolerant the camera should be of changes in subject distance and position within the frame and combine them into a series of presets, targeted towards certain types of subject movement. The aim is to make it easier to choose the correct setting for the subject you've chosen to shoot.

The six presets can be adjusted, if they're not quite giving you the results you want, but even in their default states they already cover a pretty broad range of subject behaviors.

However, while these options are the same as those offered on the EOS 5D Mark III, the 5DS and SR have higher-resolution metering sensors to build up an understanding of the scene, so should be better at identifying and tracking subjects are they move around. This 'Intelligent Tracking and Recognition' mode (iTR) is engaged using the 'Auto AF pt sel.:EOS iTR AF' setting on the fourth page of the AF section of the main menu. Without it engaged, the camera will only use depth information from its phase detection AF sensor.

Low Light Focus

The autofocus is formally rated down as far as -2EV but in our testing we found the central point to perform similarly well to the Nikon D750, which is rated down to -3EV. Click here to see it in use at -2 EV, and see our demonstration of the 5D Mark III's AF module performing down to -3 EV with its central point in our shootout vs. the Nikon D750, D810, and 7D Mark II. It's worth noting that Nikon's nearest competitor, the D810, often refuses to focus in light levels as bright as -1 EV using its central point, making it far worse than the 5DS/R, and even the D800/E, all of which focus in 4x dimmer conditions (-3 EV). 

Continuous AF: Long Distance Subjects (Telephoto)

As you might expect, the camera is extremely good at refocusing on a subject coming directly towards it using a single AF point, whether it's a long distance subject shot with a telephoto lens (below), or a shorter distance subject shot with a wide, fast prime (see here). This is a task that DSLR phase detection autofocus is particularly good at and Canon has a lot of experience of creating algorithms that predict subject distance, based on existing movement.

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Looking closely at these images, you can see that the camera has an extremely high success rate, with any misfocus being extremely subtle and slight motion blur being more of a problem than any slight focus imprecision.

Zone AF: Center (with iTR)

Zone AF allows you select a 3x3 central or 4x3 peripheral region and allow the camera to automatically select which point within that region to use. This can help when it's difficult to keep a single AF point over a moving subject. Theoretically, we'd expect this AF mode to be augmented by Canon's Intelligent Tracking and Recognition (iTR), so we put it to the test to see how well the camera stuck to our approaching cyclist. Unfortunately, even with the camera restricted to a central zone of autofocus points (so that it couldn't go far wrong), the additional challenge for the camera of having to choose which AF point to use results in a lower hit-rate than before.

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As you can see: the hit rate drops a little, with a couple of frames being more obviously out-of-focus, but overall the camera is still doing a good job of maintaining a good hit rate and a reasonable shooting speed.

iTR Multi Area AF (61 point mode, cross-type points only)

We then let iTR try to track the subject across all of the camera's 41 cross-type AF points, as we have our subject weave left and right while riding towards the camera. In this mode, we initially designate our subject by selecting the center AF point, placing it over our subject, and initiating AF. As long as the shutter button remains half-pressed, the camera attempts to select the appropriate AF point(s) to stick with the subject, no matter where it moves to within the frame.

The system does pretty well at working out which subject to follow, and generally speaking we've found this sort of subject tracking to work quite well on Canon cameras as long as you have a subject pretty well isolated in depth (in this case, a single cyclist, with much of the rest of the frame containing distant objects distinctly behind our cyclist). However, the camera didn't necessarily do a good job at keeping up with our weaving cyclist. This led to a number of sub-optimally focused shots, as you can see in the rollover below.

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To test what influence the AF parameters would have, we tested both Case 1 and Case 6 (which is tuned to expect more acceleration/deceleration and to be more willing to switch between AF points). We got a significant number of in-focus shots with Case 1, though not always as perfectly focused as the shots achieved with simpler AF modes. Case 6 saw the number of in-focus images drop still lower, for this shooting scenario.

Interestingly, the AF point indicated in the viewfinder would often lag a little behind the subject but the camera would continue to hit focus in approximately the correct place (possibly because its ability to predict the subject's distance is better than its ability to keep up with the subject's position in the scene).