10-06-2018 08:45 PM
Nice to hear from you again, Wadizzle. Thanks for the response.
Things can get really muddy when reading various documents and watching related videos. For example, although not relevant to my situation of using 5-point Expansion, where I first identify the target for the AF system by covering it with the AF pattern, there appear to be instances where the camera does actually know one subject from another. A couple of examples, if I understand this stuff correctly. First, face recognition. My understanding is that the camera has the ability to recognize that face A is not the same as face B. Second, EOS iTR. EOS iTR uses size, shape, and color of a subject (in addition to contrast and other "usual" or "normal" criteria) to assist in tracking it. No details are available for any of this, as far as I know, but it seems to me it is possible that in these two situations (face recognition and EOS iTR) the camera does indeed know one subject from another.
Your second paragraph is an example, it seems to me, of how difficult it is for a user to really understand just how all of this works, based on available documentation and "help" services available (see Rodger's last two replies, also). Canon's 7D2 (I know, it is a cheap box compared to a 1Dx, but the AF tracking systems seem to have a lot in common) owner's manual, page 115, says that if a subject "moves away from the AF point, the camera switches its focus to neighboring AF points to continue focusing on the subject. The camera switches to the AF point deemed most likely to focus on the subject based on the subject's continual movement, contrast, etc." I interpret that to mean the camera will change from the original AF point (the pattern - Canon allows up to 65 points to be called a singular Active AF Point) to some other point(s) in order to try to regain the subject." Note the language "deemed most likely to focus on the subject." Deeming is based on the subject's pattern of "continual movement." But, without understanding what the subject looks like, how does the system know it has acquired the correct target? Bottom line, when the target disappears from the radar, if AFPS is set to +1 or +2, the camera is going to (immediately) go looking for the subject amongst adjacent AF points.
Onward to TS: with this same loss of target, TS is going to delay refocusing (by switching AF points?), as you rightly point out (page 113 of the same owner's manual). So, TS throws out the anchor to slow the ship down, while at the same instant AFPS says "full speed ahead." To me, that sets up a conflicting priorities and conflicting operations situation - back to my earlier comment: "This would seem to be an unwinnable head-butting exercise to be managed in realtime by the camera's AF firmware."
I hasten to add one more observation. This appears to prove the points I've been trying to make the last couple of days. Take note that not one of the 6 "factory" (default) AF Cases sets up what would seem to me to be the kind of conflicting situation just described between TS and AFPS settings. The Cases are an excellent provision in their default settings, and Canon's documentation is clear about tweaking their settings and the results of doing that. Where that falls short is in not defining where conflicting priorities can be introduced in a single Case. And that's the point of all of this.
My information comes from Canon's own documentation (as also supported by the 7D2 AF-Setting Guidebook). This kind of understanding or lack of understanding or misunderstanding could at least be ameliorated, if not eliminated, by appropriate resources being made available to camera users, it would seem to me.
One way to describe today's superb, complex cameras is to speak of them as a potent microcomputer that hosts and directs optical resources to produce extreme-quality results. But users need to clearly understand how these wonderful beasties work and how to successfully apply that understanding and technology. So, back to my earlier point: users need to be made aware of potentially conflicting situations in the way they assign values within each user-controllable parameter. The AF-Setting Guidebook is a really good resource. Is it time to update and expand it? I wonder what Canon would say to all of this. This CanonCommunity seems to be the best forum for bringing up these kind of questions.
Thanks, again, to Rodger for bringing up the Corvette/GM example, in his last response to this issue.
10-07-2018 06:23 PM - edited 10-07-2018 06:25 PM
Nice to hear from you again, Wadizzle. Thanks for the response..
Onward to TS: with this same loss of target, TS is going to delay refocusing (by switching AF points?), as you rightly point out (page 113 of the same owner's manual). So, TS throws out the anchor to slow the ship down, while at the same instant AFPS says "full speed ahead." To me, that sets up a conflicting priorities and conflicting operations situation - back to my earlier comment: "This would seem to be an unwinnable head-butting exercise to be managed in realtime by the camera's AF firmware.".
You can find the EOS-1D X Mark II AF Guidebook at this link. It explains the AF system in depth. 140 pages of depth. Click on the “Brochures” button.
There is no conflict with that combination of settings. I would also advise using the entire center zone of AF points, if not all of them.
Yes, the camera can recognize a subject and track it, which is a very different scenario from your question about a subject dropping off the radar. When you reacquire the subject, the camera does not know, or even care, whether or not it is the original subject. It has acquired a target, and it goes to work.
I think you are forgetting about what happens when the subject “drops of the radar” for the scenario you describe above. Yes, the camera stops refocusing itself for a beat. It does this even though the focus tracking is resetting itself and looking for a new target.
Normally, when people lose a subject, they may briefly release the shutter, and then half press it again as they reacquire the subject. That can take a lot of time when you are talking about 10-14 FPS.. Another technique I have heard about is to program the [AF-ON] button to be AF-STOP. Tapping it will have the same effect as releasing the shutter and pressing it again. But, this can take time, too, but not as much. It also requires some thought and instinctive action on your part.
With those “conflicting” settings, the camera will momentarily stop itself from focusing, and begin looking for a target at your selected or registered AF point, typically the center AF point in most cases. When the focusing resumes.
One setting controls focusing behavior, while the other controls tracking behavior. They are able to happily coexist. Yes, AFPS may say full speed ahead, but focus does not change until the “beat” expires. Hopefully, you have your subject under the initial AF point again. I think the photographer loses less time with this automatic behavior, compared to initiating it manually by pushing and releasing buttons.
10-09-2018 02:37 PM
Thanks again, Wadizzle, for your time, references, info, and advice. I have downloaded and am reading materials. Nice that someone will spend this kind of effort helping another dedicated Canon user (for more than 50 years).