Less AF Points When Tracking?

Discussion in 'Beyond the Basics' started by HeldInTheMoment, Nov 9, 2015.

  1. HeldInTheMoment

    HeldInTheMoment No longer a newbie, moving up!

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    I was just watching some YouTube videos to learn some new tricks for my photography and I came across one that lowered the AF Points for Continuous Tracking. Can anyone share with me if this is accurate and what the benefits are?

    Thanks!


     
  2. Derrel

    Derrel Mr. Rain Cloud

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    Depending on the camera there are 1-point, 9-point, 11-point ,21-point, and 51-point autofocusing methods. Not all subjects are the same; birds in flight against a solid-color sky is one type of subject; North American football with 22 players wearing high-contrast uniforms with bold numbers and scattered over a playing field in clusters is another type of subject. We have no idea what the video you watched said, and no idea how skilled or proficient the video's author was. Small-sensor cameras with pokey f/3.5~5.6 telezooms like 55-200 have almost no foreground/background separation capabilities at outdoor sports distances of 30 meters, whereas a 300/2.8 shot on FX has substantial foreground/background separation capability. Using slow consumer-aperture zoom lenses, or short focal length lenses like 18-140mm is vastly different from using say a 70-200/2.8 in a single-player sport like say, tennis.

    Autofocusing is a complicated subject, and exactly "how" to set up a camera depends to an extent on the camera, its AF module, and its strength, as well as the lens, and how the lens and its length and aperture send data to the AF system. FAST telephoto lenses give the AF system very much IN-focus and very much OUT-of focus data to work with, and tele focal lengths cover a narrow angle of view, and AF system response can be blazingly fast. Slooooooow, short length lenses, like say 18-55 or 18-135 for example, cover pretty wide angles at their shorter end, and at their longer end, the in-focus or out-of-focus data the lens sends to the AF module is not so nearly clear-cut as with say, a 300 f/4 or even the 70-200/2.8, so these types of lenses with say, a 51-point AF pattern engaged and at 18-70mm are going to have a TON of real world area covered by a 51-point pattern.

    Wide-angle lenses mean that each and every AF bracket represents a LOT of real-world real estate; tele lenses make each AF bracket cover a much smaller part of the real,actual world. One needs to understand a number of technical aspects of exactly HOW a camera's AF system has been designed to work, and these systems are not exactly simple, plus some of the set-up procedures can be tricky. Lock-On in Nikon-speak for example, means almost exactly the opposite of what a typical noob would assume it means, and many people set it exactly bass-ackwards, and it causes problems.

    A 51-point AF pattern with a 300mm lens can lock on to a single runner or single horse with ease, and follow it, no issues; on a DX Nikon body an 18mm lens at 30 yards is going to cover a huge horizontal field, so using a lot of focusing points might not always be the best idea. or, it might be a great idea. It all depends.
     
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  3. HeldInTheMoment

    HeldInTheMoment No longer a newbie, moving up!

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    Point taken, let me clarify...It was a professional photographer using a 70-200mm f/2.8 tracking a person skateboarding at a skate park.
     
  4. tirediron

    tirediron Watch the Birdy! Staff Member Supporting Member

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    I rarely use more than a single AF point for anything.
     
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  5. Derrel

    Derrel Mr. Rain Cloud

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    Let's put it this way: the best camera I've ever had for action shooting was the Nikon D2x, which was an APS-C camera with an 11-area AF system, with 9 of the 11 sensors being cross-type. For action work in soccer, track and field, baseball, whatever, the absolute best focus tracking and the fastest focus acquisition I ever have been able to get was when using its group dynamic AF in continuous focusing, with a group of four AF points active at one time, with the focus priority always set to release, favoring faster firing at the expense of focusing. I would use the controller to pick my target, and the camera could lock on and follow even erratic action amazingly well!

    Single-point, center AF is not always the best for action; additionally, the user is supposed to MANUALLY select the initial AF location using the 4-way controller, and then based on that subject's RGB color analysis, the metering system feeds color data to the focusing system, and THAT is how the system can "follow" action subjects. Was that discussed in the videos? Because that is a critical aspect that many people overlook.

    A single person in a skatepark with a 70-200/2.8 AF-S focusing lens is not really an exceptionally difficult subject, and it likely to take up a very large part of the frame, plus the subject is going to move smoothly (it's on wheels) and not all that fast either. With an APS-C camera at skatepark distances, a 70-200 is gonna be TIGHT in its angle of view over most of its length.

    Again...3-D tracking focus is helped by having the user select the desired target by using the 4-way controller and placing the desired subject under an AF point, and then the system "sees" the target. Many people do not do this initial step. One can allow the camera to choose the AF points...

    Fewer AF points is not always the right idea when tracking moving subjects. On the full-frame cameras even a 21-point AF scheme covers mostly the central-most area of the viewfinder. On the crop-frame Nikons the AF brackets go way out to the margins of the viewfinder. 11- and 21-point AF works pretty well for me. I really think that single-point AF is misguided for following action in the Nikon cameras I have owned; it cripples the camera's systems by eliminating ANY, as in ANY chance of using even one or two close points to keep the focus locked on the subject, which might be low in contrast, like a dark horse, or the side of a white boat, or the Wilson High track runners and their dark green, number-less jersey fronts. Again...Nikon is using high-speed color AND distance analysis for 3-D focus tracking.

    The group dynamic 4-point cluster in the D2x could track pole vaulters coming down the runway, and as they planted and moved upward on the "pull", as they crossed the bar, and as they fell, all by using the camera in "tall" mode and having a small group of 4 points active at the top of the frame...if only the center point was active, the subject would NOT be in the middle of the frame much of the time.

    Many people are looking for a panacea, a one-size fits all approach, but AF is a complex issue. I would suggest buying the Thom Hogan Guide To The Nikon ________ for your camera, and there you'll be exposed to a hundred pages worth of information about the nuances of how modern Nikon AF systems work, and how and when to try what settings. We've basically moved to 21st Century technology, yet many people are using these cameras as if it's an F4 with ONE, single, smack-dab-middle-of-the-viewfinder AF bracket. You'll find that a lot of birders like the 21-point AF setup. I find 11 point AF pretty reliable.

    The whole issue goes back to the source: YouTube videos. Can they always be trusted, implicitly? How accurate is the info, and how appropriate is it to YOUR situation?
     
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  6. Dave442

    Dave442 Been spending a lot of time on here!

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    Then you also have to compare what the pro was using vs. your equipment. The Nikon Pro bodies are known to be much better at processing the AF data faster.

    I also read what you did about using fewer focus points. The reason given in what I read was to lessen the burden on the AF processor. I think your options are Single point, 9 point, 21 point or 51 point. The literature just says 9-point for predictably moving, 21-point for erratic moving and 51-point for when your lucky to keep the subject in the viewfinder.

    For sports I usually go into the lowest Dynamic Area focusing option. However, what I did at a skate/bike competition exactly two years ago was just single point and I prefocused at the ramp and then focused again on the person as they did their trick right before taking the shot (pretty much what people were doing 100 years ago in photography).
     
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  7. astroNikon

    astroNikon 'ya all Bananas I tell 'ya Supporting Member

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    Tracking a single person skateboarding, which would have a consistent flow and smooth direction changes, sounds like a fairly easy situation to me as Derrel has pointed out above.

    Compare that to say, a fluttering butterfly, which is erratic at best.
     
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  8. JacaRanda

    JacaRanda Hobbyist Birdographer

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    It would be nice if you posted the link so that others may see exactly what you have.

    Guess it would have helped to click 'post reply' on this earlier.
     
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  9. JacaRanda

    JacaRanda Hobbyist Birdographer

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    When I first got my second camera, all I did initially was #1 rtfm and #2 watch several videos (official videos from the maker) and #3 practice using every scenario I could think of that the camera would allow (on mostly birds in flight). All I was concerned with was AF. My first 1000-2000 clicks were prior to LR adding the camera profile.

    If you are able to, get out and practice with your camera. Don't worry so much about the image and quality, rather how your different AF scenarios work and work best for you.
     
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  10. DarkShadow

    DarkShadow Birdographer Supporting Member

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    I use single center point only for everything.Birds In flight included.
     
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  11. HeldInTheMoment

    HeldInTheMoment No longer a newbie, moving up!

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    Here is the link to the video, I guess it was obvious I should have done this before:

    I was just curious as to the reasoning to lowering the AF points, but with the great community here I was able to learn much much more!

    Thanks All!!!
     
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  12. astroNikon

    astroNikon 'ya all Bananas I tell 'ya Supporting Member

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    It's FRO
    using the top cameras from Nikon and Canon lol

    on the Nikon he's at 1/1600 with VR ON ? thought that was a no-no.
     
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