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Thread: AF mode selection w 5D MKIII - not so great performance?

  1. #1
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    AF mode selection w 5D MKIII - not so great performance?

    I've been trying to shoot action shots of my little black dog running toward me chasing sticks tossed by my wife and not getting too many keepers. Conditions - either backlit or front, Av mode at f4 w 600 f/4 II, IS mode 3, shutter speed 1/1000 or higher, high-speed continuous, AF mode 4 (rapid accelerating subjects), central AF single point selection, shot from monopod. I get multiple images with the active AF sensor directly on the subject but they are completely out of focus. I have tried tracking well in advance of the shutter release but this lens/camera/photographer combo hasn't had much success to this point. Is this just too tough a subject? She is a very fast dog and a very black dog but I'd love to capture the joy on her face as she bounces along in pursuit. Would the 1DX do much better? Same AF system but better performance in the 1DX? My lens is not one of the firmware update versions that needed an AF adjustment and I have tuned it for focus microadjustment as described on the "birds are art" site - works fine for other subjects. Here's a sample that is OK, not great....Click image for larger version. 

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    Should I change the individual settings to create a custom AF for this subject? Advice welcomed.

  2. #2
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    I have no problem tracking my black dog with my 1D IV and 500mm f/4 running full bore at me. Mine is a larger dog but I think you should be able to with the equipment you have. I do not own the 5D III so can't speak to your settings, but if it really does have an AF superior to the 1D IV you shouldn't have trouble with this.

    If you have an option to enable supporting or surrounding points it should be turned on as well. Some bodies refer to them as assist points.

    You should be tracking on the dog, not ahead of it or advance.

  3. #3
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    Also, and it may be obvious, make sure your drive mode is AI Servo and not single shot. With such a high shutter speed I would also turn off IS.

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    As said, ensure you have AI Servo mode enabled. Also, 1/1000s is NOT enough for a fast dog. It can work for a side shot if you're panning with the dog (and the grass will be a bit blurred). You want a speed closer to 1/2000s, or more. I have a few shots where 1/4000s was still motion blurred, but they're rare.

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    I was just reading the 5D III manual. The setting "rapid accelerating subjects" is a AI Servo mode, I am assuming you did change to AI Servo.

    Also, I think Case 5 "For erratic subjects moving quickly in any direction" would be the better setting for a dog that bounces arround. It is on page 87 of the manual.
    For this case you should be in AF point expansion (Manual selection), AF point expansion (Manual selection, surronding points), Zone AF (Manual Selection) or 61- point automatic selection AF. All of these expand the area from one point so surronding points will track once the first looses the object.

  6. #6
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    Since the 5dIII handles high ISO so well you could try Tv mode with shutter speed of 1/4000 and set the ISO to Auto. With AI servo drive mode of course.

  7. #7
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    I think the key to your problem might be the SINGLE POINT AF selection.

    With 61 available AF points, any time you're using one single AF point, you're dealing with a relatively small area of AF coverage. Even though the actual area covered by an AF point does extend beyond the area you see in the viewfinder, it remains a very small portion of the entire focus screen – and with many subjects, a small part of the subject you're trying to focus upon.

    I highly recommend expanding on the single point AF selection in this scenario,(single point has some trouble with rapidly moving subjects) I think you will find the AF will track and lock more efficiently and result in more keepers.

    At least try the AF Point Expansion/Surround. Expansion (4 point) Surround (9 point).

    The Zone AF option expands the active AF points to 9 or 12 but selects the closest object which may not be your subject.

    Try AF Point Expansion/Surround


    If you are really interested you can go into the AF MENU OPTIONS to adjust tracking sensitivity.
    Last edited by iND; 11-20-2012 at 05:44 PM.

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    It has also occurred to me that just turning on AI Servo isn't enough. You need to know how to use AI Servo.

    When you press the shutter half-way, the camera starts tracking motion. It will need a second before it's figured out speed, acceleration, etc. If you fully depress the shutter before it knows how to track, you'll get a mis-focused image.

    While the camera is tracking, you must keep the AF point (or points) over the subject.

    Once you're tracking and you fully press the shutter, two things can happen. Older cameras will do what I describe first, and newer ones, I believe, let you choose to skip part one.

    1. The camera takes the shot at the current focus distance. You said, 'the the picture, NOW!' and the camera did it. By the time shutter lag, etc are factored in, the subject may have moved out of your depth of field (in focus area).

    2. The camera is in continuous burst mode, or a newer camera lets you choose 'focus' over 'shutter' priority. In this case, the camera is not only tracking, but predicting. Keep your focus point on the subject as the burst fires. This can be tricky. There may be a delay between shots as the camera recalibrates, re-predicts, and refocuses. Unlike the first shot, these shots will be taken when the camera has figured out where the subject WILL BE when the shutter opens, not where it was during tracking. These should be sharper than image 1 in the burst.

    I found out about this two-step process from an ancient EOS-1 film camera white paper I found online. I've never seen anybody or anything else mention it (aside from me, here on TDP). From my experience, it holds true on my T1i. I think I remember seeing a setting on my 7D to choose the priority, such that the first image will be taken when the camera is predicting, not when you press the shutter, but I'm not sure. I haven't done extensive testing on my 1Ds, but I imagine it follows this two step procedure as well.

  9. #9
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    Quote Originally Posted by DavidEccleston View Post
    It has also occurred to me that just turning on AI Servo isn't enough. You need to know how to use AI Servo.

    When you press the shutter half-way, the camera starts tracking motion. It will need a second before it's figured out speed, acceleration, etc. If you fully depress the shutter before it knows how to track, you'll get a mis-focused image.

    While the camera is tracking, you must keep the AF point (or points) over the subject.

    Once you're tracking and you fully press the shutter, two things can happen. Older cameras will do what I describe first, and newer ones, I believe, let you choose to skip part one.

    1. The camera takes the shot at the current focus distance. You said, 'the the picture, NOW!' and the camera did it. By the time shutter lag, etc are factored in, the subject may have moved out of your depth of field (in focus area).

    2. The camera is in continuous burst mode, or a newer camera lets you choose 'focus' over 'shutter' priority. In this case, the camera is not only tracking, but predicting. Keep your focus point on the subject as the burst fires. This can be tricky. There may be a delay between shots as the camera recalibrates, re-predicts, and refocuses. Unlike the first shot, these shots will be taken when the camera has figured out where the subject WILL BE when the shutter opens, not where it was during tracking. These should be sharper than image 1 in the burst.

    I found out about this two-step process from an ancient EOS-1 film camera white paper I found online. I've never seen anybody or anything else mention it (aside from me, here on TDP). From my experience, it holds true on my T1i. I think I remember seeing a setting on my 7D to choose the priority, such that the first image will be taken when the camera is predicting, not when you press the shutter, but I'm not sure. I haven't done extensive testing on my 1Ds, but I imagine it follows this two step procedure as well.
    One solution to this issue is to use one of the back buttons to focus rather than the 1/2 shutter press(this can done with one of the custom functions) ....this way you can focus continuously or intermittently with your right thumb and snap the shutter whenever you wish with your right index finger....it's called rear focus and it works great with birds in flight.

  10. #10
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    Thanks a lot for for the advice. I was using AI servo but will increase the shutter speed (up the ISO) and expand the AF point plus turn off IS. I've switched to rear focus only so work the shutter and AF separately. I've been giving the AF plenty of time to warm up by tracking the dog before shooting but it just hasn't caught up to her consistently. Since many of the OOF shots show the AF point directly on the dog's head on review, I assumed the camera is pointed in the right direction anyway.

    Shutter speed is a good point - until I have that high enough, no need to assume the AF isn't tracking. Per HDnitehawk, I will also play with mode 5 for erratic subjects. After all the rave reviews on the AF for the 5D MKIII, I'd like to learn to make it work. I usually assume that I am the weakest link.... Thanks again.

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