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I've been doing some experiments with my AI Servo Autofocus system in my 1DX Mk ii. Basically, the experiments were intended to help me understand some of the rather confusing jargon used to describe the functioning of the AI Servo Autofocus system, and how to configure it properly for my needs.

My experiments involved watching the AF point display through the viewfinder while watching a moving object I set up moved through the focus area. This all worked well enough viewing through the viewfinder. I can see the selected focus points more or less 'track' the moving object as it moved back and forth through the viewfinder.

Being a lazy person, I thought that I would watch this in "Live View" instead of through the viewfinder. I don't use Live View much, but I thought it would allow me to watch the AI Servo system at work while leaning back in a comfortable chair sipping a cup of coffee instead of being humped over the camera squinting into the viewfinder. :P

To my apparent disappointment, however, it seems that what I have learned is that the AI Servo system does not work in Live View on the 1DX Mk ii. Even more disappointing is that this limitation does not exist on (at least some versions of) the Canon Mark 7D.

I've just spent about an hour looking through the documentation and searching online in an effort to: a) confirm this limitation, and b) understand the engineering or technical basis behind it. All I've been able to find so far is this:

  • a line in the 1DX Mk ii Reference Manual (p.280) that says, "AF method You can select [:-)+Tracking] {OP note: "face tracking" in other words} or [FlexiZone - Single].",
  • this review of the 1DX Mk ii that lists the following as a "con":

    AI Servo does not support Live View mode.

My questions are as follows:

  1. Can anyone confirm that this is a hard and fast limitation?
  2. Does anyone know the basis/reason why Canon might have chosen to disable this feature on their "flagship" camera model, yet enable it on a model that costs about one-fourth the price?
  • No Canon DSLR of which I am aware does "AI Servo" in Live View. I have both a 7D and 7D Mark II, so I can conclusively say that you are incorrect in your assumption that one of the 7D series does what you think it does. The 7D Mark II does offer "Dual Pixel CMOS AF" in Live View, which is more or less the functional equivalent of AI Servo in terms of tracking subjects, but it doesn't display AF points on the screen while doing so. I'm pretty sure the 1D X Mark II also offers Dual Pixel CMOS AF in LV. – Michael C Oct 28 at 3:21
  • The 7D Mk ii belongs to a friend... It may not be called "AI Servo", but it does show the focus points that move around as the object in focus moves. But let me get some more specifics & I'll post a follow up w/ the details. – Seamus Oct 28 at 23:25
  • @MichaelC: The 1DX Mk ii has 2 options in the AF function in Live View. The 7D Mkii has 3 options in the Live View, AF Method: 1. :)+Tracking, 2. FlexiZoneAF(), 3. FlexiZoneAF[] . In the 2nd option, focus points are displayed in the Live View display that move as the object moves. So you're correct in that it's not called "AI Servo", but it most certainly does display AF points that track the target (which is to say that they appear to track an object that moves across the field of view in Live View display). – Seamus Oct 28 at 23:59
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DISCLAIMER: This is more hypothesis than definitive answer. I continue to research this, and will update the answer when and if I find new information. In the meantime, please don't let my "guess" dissuade anyone from answering definitively. I'll accept the first correct definitive answer, and my answer is not definitive at present!

Q1: Can anyone confirm that this is a hard and fast limitation?

Based on some material I've seen, AI Servo focusing is not available when using Live View on the Canon 1DX Mkii. This is a hard and fast limitation for the Canon 1DX Mkii: AI Servo uses 'phase detection' technology. The sensor utilized for phase detection in the 1DX Mkii requires that the reflex mirror be in the "down" position; i.e. positioned to direct light coming through the lens to the viewfinder instead of the sensor. Live View otoh, positions the reflex mirror in the "up" position. No light is transmitted to the phase detection sensor when the mirror is in the "up" position, and therefore the AI Servo AF subsystem can not function in Live View.

The 1DX Mkii does offer AF in Live View, but it is contrast detection AF, as opposed to phase detection AF. Note that phase detection AF has an advantage over contrast detection AF in that it is much faster.

Q2: Does anyone know the basis/reason why Canon might have chosen to disable this feature on their "flagship" camera model, yet enable it on a model that costs about one-fourth the price?

As @xenoid has pointed out, the "3rd mode" of focusing (labeled FlexiZoneAF() in the configuration menu, aka FlexiZoneAF multi) in the 7D Mkii is NOT labeled as "AI Servo". However, with selection of the Continuous Focus and FlexiZoneAF() options in the Live View menu, the 7D Mkii does provide what could be correctly categorized as an automated, servo-based autofocus system based on phase detection technology*. Not "AI Servo" perhaps, but certainly more functionality than offered in the 1DX Mkii!

Note* The 7D Mkii's Continuous FlexiZoneAF in Live View also utilizes phase detection AF technology! Canon has accomplished this on the 7D Mkii through utilizing one pixel of the "Dual pixel CMOS sensor" (imaging sensor) to perform the phase detection function. See this video for visualization. In other words, Canon utilizes the imaging sensor to perform both imaging and phase-detection focus measurement simultaneously in Live View. Note also that the 1DX Mkii also uses a "Dual pixel CMOS sensor"; the only apparent difference in the sensors being that the 7D Mkii sensor is smaller in size ("cropped sensor") than the 1DX Mkii's "full frame" sensor.

Perhaps compounding the confusion, the 7D Mkii was released approximately 18 months before the 1DX Mkii was released. One might easily imagine that this would have given Canon sufficient time to incorporate the feature into the 1DX Mkii.

Unless Canon has published an explanation, any answer to this question demands speculation as to motive. As far as I know, Canon has published no such explanation.

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Your could be mistaken, it doesn't seem enabled on the 7D Mk2 either:

From DPReview:

Sadly the knowledge of subject distance that this system gives isn't used to provide tracking autofocus in live view mode - like the 70D, the 7D II doesn't attempt to refocus in live view when continuous shooting.

  • Sadly, the reviewers at DP Review aren't familiar enough with Canon's sophisticated AF systems to even set them up properly for many of their AF tests, or even with Canon's lens lineup enough to understand why they couldn't get the 90D to do what they wanted when they were using a consumer grade EF-S 18-135mm STM lens (optimized for slow, smooth focusing during video recording) to rate the 90D for tracking shooting stills. Just read the comments at their 90D review! – Michael C Oct 28 at 3:28
  • They also choose to do a test with uncontrolled variables in lighting that can significantly impact the results of their "bicycle AF test." The face is well lit for tests of some cameras, while it is in dark shadows in tests for other cameras. Again, see the comments in the review linked above. – Michael C Oct 28 at 3:31
  • The 7D Mkii has 3 options in the Live View, AF Method: 1. :)+Tracking, 2. FlexiZoneAF(), 3. FlexiZoneAF[] . In the 2nd option, focus points are displayed in the Live View display that move as the object moves. It's not "AI Servo", but it does display AF points that track the target. That is to say that the AF points appear to track an object that moves across the field of view in Live View display on the 7D Mkii, much like the AI Servo AF points behave when viewed through the viewfinder in the 1DX Mkii). – Seamus Oct 30 at 21:24

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