# Q: 5d3 Autofocus squares in viewfinder - tracking



## WSMyles (Jan 19, 2013)

Situation: AF Case #6, erratic movement. AI Servo. 4- or 8-point expansion enabled.
AF/Meter start on the subject with centre AF point.

Subject (dogs at play, at great speed!) moves all over the field, I keep it within the 61 AF points and eventually I see a shot and press the shutter all the way. Despite the fact that the reticle display never moved from the original "lock on," the shot is properly focussed, though the subject is no longer "under" the original 5 points. The AF system seems to be "invisibly" tracking the subject and maintaining focus while confusing me (the operator) by displaying the point originally locked on rather than the current locked point.


Q: Is there a way to have the viewfinder AF display track and continuously display the *active *AF point in real-time, rather than "going out" soon after it locks on? I've tried the 4-point (preferred) and 8-point expansion modes. Zone AF is too much of a blunderbuss for my purposes. 

I haven't spelunked all the Custom Functions yet, but my reading of the manual suggests that my expectations and intuition are wrong - that is, the viewfinder AF squares do NOT track the active AF point after locking on and until the shutter fires. I have it set in AF5 to display in modes 1,2,4. That is, everything but "always on 61point." It does indeed display, but doesn't move with the subject. YES, I am using Ai Servo and it seems to do more than the manual suggests (p103/104).

Is there any way to get the VF reticle to track this way? I'm just getting to know the camera (frame #241 today!) but my hit-rate today for focus was nearly 95% - way up on the 40-60% for my 30d under the same circumstances. 

For the moment, I'm just using the centre AF point in 4-way expansion mode for focus acquisition, and the camera seems to track correctly over the other AF points despite still showing the "active" AF point as the centre. In playback, on the LCD, the red square is where it should be, and rarely the centre point 

This is more of a confidence thing than anything else - I'm conditioned to expect poor tracking performance, so I want the 'crutch' of knowing where the camera is aiming for. Am I making sense? Thanks for any insights.


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## bjd (Jan 19, 2013)

Hmm,
try the following, 61 points, AI Servo, focus on something near a center point, keep the shutter release half-pressed, then slowly move the camera away (left or right). I see other AF points trying to follow the object until its no longer under an AF point.

Load the file into DPP; there you can (ALT+L) display the AF points used, and those that had lock (red).

Hope I understood you correctly?

Cheers


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## J.R. (Jan 19, 2013)

This is perfectly normal. In AIServo mode, only the selected point will light up even if the expansion assist point is active. The expanded point will not light up and there is no way to do this in camera.


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## WSMyles (Jan 19, 2013)

Hi bjd,
Yes, you are describing exactly what I expect to see - the AF "HUD" showing in real-time what it has locked on to, even though it has shifted.

I tried a few variations on the interpretation of "61-point" before changing the AF display to "_constant 61 point_" (changing the available points through the reticle/M.Fn didn't help).

Then I tried turning off point expansion (above/below/left/right and the 8 points around) and voila!

When I do this, it DOES indeed track! AF5 Mode 1,2 and 4 don't but mode 3 does 

There must be a reason why it only works in this one combination of modes (but still tracks invisibly). Given enough time, that reason may become apparent.

Summary: 
it seems that in order for this to work, the AF mode needs to be All 61 points (ie, all the points in the VF and the curved brackets as well) _AND_ set to single point (no expansion) _AND _the AF5 display mode set to *ALL (Constant)* or *SELECTED (Constant)*

Thanks, bjd and J.R. -- mission accomplished


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## East Wind Photography (Jan 19, 2013)

Regardless of what is displayed in the viewfinder AI Servo was designed to be predictive not only calculating velocity but also acceleration and deceleration. The case modes shift the priorities slightly in the algorithm based on the type of subject you are shooting. I rarely use case 6 and when I do I have the sliders adjusted to maximize lock, maximize tracking and ignore anything that comes into view.

So what the AI in AI Servo does is tracks accel and velocity of the targeted point from the moment it gets first lock and as long as the shutter button his held down will predict where the focus should be when the shutter activates. So in your case where the subject is in focus and then drifts out, the camera has already calculated the acceleration and velocity and on the next shot has predicted where it should be.

Depending on the case selected the camera may re-acquire on something in the background. It all depends on what you are shooting and try all cases in certain circumstances will give a feel for which is best.

Most people don't understand what's going on in the background when they select one case or another and then blaim the camera is not working right. Granted it is more complex than older models but when you have the case settings adjusted for what you are shooting you can get incredible results. With the 5d3 properly set I can track eagles against noisy backgrounds. I could never get that reliably with a 7d or lower model.


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## bjd (Jan 19, 2013)

WSMyles said:


> Hi bjd,
> Yes, you are describing exactly what I expect to see - the AF "HUD" showing in real-time what it has locked on to, even though it has shifted.
> 
> I tried a few variations on the interpretation of "61-point" before changing the AF display to "_constant 61 point_" (changing the available points through the reticle/M.Fn didn't help).
> ...


FWIW,
I installed the Exif Meta LR plugin today. It allows you to display a lot of EXIF data, e.g how many AF points were in Focus, how many selected, and loads of other stuff. I'm still fighting with configuration of the plugin, but that info may answer some of your (and my) questions.

Cheers


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## WSMyles (Jan 20, 2013)

East Wind Photography said:


> Most people don't understand what's going on in the background when they select one case or another and then blaim the camera is not working right.



I haven't been working with it long enough to blame the camera for anything yet 

The gist of my initial inquiry is: why doesn't the camera SHOW you what it is tracking because it evidently IS doing it anyway? The shots and metadata show it.

The answer seems to be: it will, but _only in selected modes._.. opening a different can of worms: _why_? 

Case #1 didn't handle the same scenario very well (though I've since learned quite a bit). Case #6 is the next I tried because it "fit" the description of the shooting scenario the best. The results confirm that. A very high in-focus hit rate. It remains to be seen if zone-expansion was a factor in that success.

Since then, I've tweaked the Case#6 settings a little AND set the camera to FOCUS priority. Next shoot, I'll try those settings an then various combinations and permutations on them. Considering how little time I've spent behind the viewfinder, it's taken remarkably little time to start producing decent shots. Mostly because I'm still at the steep end of the learning curve, NOT because of any inherent limitation in the camera. In fact, unless I see something impossible in an image, my natural assumption is "I'm doing it wrong." 

I'm trying to learn it step by step, section by section. The lenses are all AFMA'd now (FoCal). Now my head is starting to wrap itself around the AF. I don't think I'll be moving from Av/Tv/AutoISO to M any time soon though


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## East Wind Photography (Jan 20, 2013)

So as explained the AI servo is predictive. It will adjust focus based on what it tracked previously. The subject may not be on any AF point when the shutter fires. The AF points are used to complete the math for when the subject is not on an AF point. It's not just tracking what's on an AF point.



WSMyles said:


> East Wind Photography said:
> 
> 
> > Most people don't understand what's going on in the background when they select one case or another and tnhen blaim the camera is not working right.
> ...


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