AuHunter

I read an article pertaining to shooting burst that said the camera/lens only focuses in-between each firing of the shutter. The implication was that say for example your camera is capable of shooting 10 fps, if you set it to shoot say 5 or 7 fps you will have a higher percentage of in focus keepers because there is more time between each shutter firing for the camera/lens to aquire proper focus. (I shoot a Canon 7D Mk ll using BBF in Ai Servo for BIF).

I am trying to decide if I buy into that or not. I find it hard to believe a major manufacture like Canon or Nikon would design a camera with 10 or more fps capability without designing the AF system to take advantage of that capability.

Any thoughts on the above??

GalaxyCat Loc: Boston, MA

I am very, very interested in this question. I am still learning.

imagemeister Loc: mid east Florida

Yes, the article is correct AFAIK for traditional moving mirror cameras. Cameras like the Sony A series SLT's have a pelical mirror to control the AF - so it can focus continually as the shutter fires ! That is how the A77II does 12 FPS. And cameras like the Canon 80D have a hybrid form of "dual pixel" focusing that is able to focus somewhat while the mirror is up.

Leicaflex Loc: Cymru

Look at the new Olympus OMD EM1 MkII, a good burst rate and no mirror.

jerryc41 Loc: Catskill Mts of NY

That sounds like splitting hairs. 10 fps or 5 fps is very fast, and I can't imagine a motor in a lens being able to focus that quickly. If the shutter fires five times in one second, there's not much time between shots. And how much is the subject going to move in a fifth of a second that would make refocusing necessary?

LFingar Loc: Claverack, NY

Your 7DII, in the AF section of the menu, gives you an AI Servo Image Priority option. You can set it for highest speed of shots, regardless of focus, or, to not allow a shot unless it is in focus. You can set it for both the initial shot of a burst, and for all subsequent shots of that burst. For some subjects and conditions if the first shot is in focus the rest likely will be, so, you can go for speed with them. Other times conditions can dictate that the focus of each shot be verified by the camera. Shooting a basketball player on the court, for example. Focus priority can slow down your burst rate though, depending on your shutter speed and the AF speed of your lens.

ronz Loc: Florida

LFingar gave you the correct fix. I also shot in BBF and A1 servo. Works great.

Mac Loc: Pittsburgh, Philadelphia now Hernando Co. Fl.

That makes sense.

Steve Perry Loc: Sylvania, Ohio

The camera can't focus when the mirror is up, the AF sensors are blocked. So, instead it uses a predictive tracking algorithm to determine what's happening with the subject when it can't "see" it during the mirror blackout. Once it sees the subject again, the new info is incorporated into the tracking system and adjusted. The lens is focusing throughout the burst however - not just just when the camera can see the subject. If it didn't you'd never get a sharp bird in flight shot because the camera would always be losing / trying to re-aquire the lock when the mirror went up and down.

In theory, less mirror blackout time can help to a point - if the camera is struggling to keep focus (if you ever lose focus on a subject you're tracking, you need to stop shooting and let the camera regain focus). At the same time however, if the camera is rated for a certain frame rate, then it's usually just fine to use that frame rate - the software / hardware is designed for it. Personally, I never drop my frame rate. I may lay off the burst if I see the camera struggle to keep a lock, but once it's back, I fire away again. The only reason I recommend dropping frame rate is if the mirror blackout is making it difficult for an inexperienced action photographer to keep track of the subject in the viewfinder and they are losing tracking because of it (in fact, that's probably why some think dropping the frame rate increases the keepers).

Thomas902 Loc: Washington DC

Steve Perry speaks with tenured wisdom... Steve is a successful commercial shooter with extensive applied experience, thus I place much credence in his thoughts here...

That said, there is possibly way too much emphasis placed on the abilities of the capture device in this thread...
My personal experience has convinced me beyond any shadow of doubt that the optic attached to the camera makes a HUGE difference in "Keeper" ratios. Case in point, I shoot the Nikon D3x for league soccer, and while it's 5 fps isn't at the top of cameras optimized for sports it does in fact, "pay the bills". What I've noticed is that my AF-S Nikkor 200-400mm f/4G IF ED VR is able to "lock" and "track" with excellent results. While my AF-S Nikkor 200-500mm f/5.6E ED VR lens is rather poor at acquiring "focus lock" and is even worse at "tracking" dynamic motion... What is even more frustrating is the camera had acquired a "lock" (as noted by the focus point used) but on too many occasions the lens hadn't pulled the lens elements into focus quickly enough...

The focus motor in the lens can and does play into the mix here... At least this has been my experience...

Since I don't shoot Canon I'm naive of it's track record other than my colleagues who do use this platform assure me that Canon's high end optics are superb...

To the OP, you are likely wasting your time trying to theorize here... Long ago I've learn from brutal experience that
"In theory there is no difference between theory and practice, however in practice there decidedly is... "

Test, test and retest... There is no other more valid way to get your head around why you are either achieve success or experiencing failure... Empirical data rules here... theory is a very poor substitute for the aforementioned...

And yes I've been trying to dump my lame AF-S Nikkor 200-500mm f/5.6E ED VR for some time now...
It is an amazing optic (price verses worth) if you are shooting static subjects...
However for dynamic motion it has been the biggest disappointment I've encountered... enough said

camerapapi Loc: Miami, Fl.

I was ready to answer your question when I saw the answer by Mr. Perry. He is an expert when it comes to the Nikon AF system.
It is precisely the lack of a mirror what makes mirrorless cameras so fast with their AF. It is my understanding the new Olympus EM-1 Mk II is capable of 20 FPS. I cannot discuss its AF because I have not used one and till recently the mirrorless cameras did not have a good AF system capable of tracking moving subjects because they have been using contrast detection in their AF system. I know the EM-1 Mk II also has phase detection sensors but I cannot make any comments on how good it is for tracking. I believe Sony also has a decent AF system but again, I do not use Sonny and I cannot make any comments.
I take pictures of BIF and action sporadically. My firing rate never exceeds 5 FPS and till now it has been adequate for me. Because my shutter is set to fire irrespective of focus many times I get a few frames that are not in focus but if I acquire focus before beginning to shoot I do better.
I guess practice is what makes us perfect.

grizrev

That’s one of the best cameras made for a wide variety of purposes!

gessman Loc: Colorado

My only thought is that I have been using Canon, and now also Sony, cameras lo these many years and have always labored under the assumption that AI Servo was designed to stay that once focus has been acquired it is locked in on a moving subject as long as the subject is visible within the frame so focusing is constantly adjusted automatically and not related to whether or not I'm firing the shutter. I'll be watching for anything that'll change my long standing impression about that if it's not too technical for me to grasp. If it is then I guess I'll just have to settle for my normally poor hit rate.

amfoto1 Loc: San Jose, Calif. USA

I shoot sports with a pair of Canon 7D Mark II... My focus "hit rate" is about 98 or 99%. My setup is AI Servo continuous focus mode (Nikon AF-C is the same), Back Button Focusing, and usually with just a single AF point, manually pre-selected. Using that, I shot a little over 5000 images at an event a few weeks ago and d\uring post-processing culled out fewer than 100 images for missed focus (I culled out a whole lot more for poor timing, poor composition or other reasons). That's fairly typical for me, after using the cameras for a couple years and getting comfortable with them. I usually take single shots or short bursts of two to four... but it really depends upon the particular action. I would NEVER slow down my frame rate trying to get "more in-focus shots" with 7DII... or with original 7D, 50D, 30D, 10D, EOS-3, Elan 7 (EOS-30) and other Canon cameras I've used over the years. Predictive AF that Steve describes above works very well, when it's used correctly. I also usually try to stop down a little, just not past the point where there's not enough background blur for my tastes. Stopping down increases depth-of-field a little, reducing how much some relatively minor focus error would matter.

IMO you're far more likely to miss focus because of...

1. Wrong focusing mode selected. I frequently hear other peoples' cameras "beeping" focus confirmation at sporting events. That tells me they're using the wrong focus mode and I know that most of their shots of moving subjects will miss focus. Nikon AF-S or Canon One Shot focus modes (for example) are "non-continuous".... These utilize the AF system to achieve focus, then stop, lock focus and give you focus confirmation (the "beep", among other things). But if the subject or you or both are moving and the distance between you is changing, the point of focus will very quickly be incorrect and the camera won't be updating it unless you consciously make the system "re-focus"... Unfortunately you can't do that quickly enough with anything moving faster than a snail. With moving subjects the best solution is to use a form of continuous focus (such as Canon AI Servo or Nikon AF-C)... These focus modes acquire focus, but never stop and lock (and thus can't ever give focus confirmation "beep", etc.), continue to sense changes in distance and adjust focus as long as you keep the focus system activated. (Note: there is a method to use a non-continuous form of focusing for moving subjects: Prefocus on a point where you know the subject will pass, then waiting for it to arrive and tripping the shutter at the precise moment.... However this is a somewehat limiting technique, won't work if the subject's movements are less predictable, etc.)

2. Over-dependence on automation... such as using All Points/Auto Selection. Multi-point AF setups leave too much up to luck, as far as I'm concerned. Sometimes it works. Sometimes it doesn't. With any multi-point setup, the camera is likely going to focus on whatever is closest and happens to be covered by one of the active AF points. For example, BIF traveling perpendicular to you, a multi-point setup will likely try to focus on the closest wingtip, rather than the bird's eye. There are times when SOME of the multi-point AF setups are useful... such very fast or erratically moving subjects... so long as there aren't distracting objects in the foreground or a busy background close behind the subject. But, generally speaking a single point is the most controllable and precise way to use AF. It does mean more work for the photographer, though.

3. Slower types of lens focus drive... For example Canon makes three primary types of focus drive mechanisms: micro motor, stepper motor (STM) and ultrasonic motor (USM). For fast action, USM is the quickest type to acquire focus and the best tracking movement. It's 2X to 4X faster than STM, according to Canon, in some lenses where there's a choice between STM and USM (such as the EF-S 18-135mm). Both are considerably faster and better tracking than micro motor, which is used mostly in more entry-level lenses. STM is quieter and smoother operating, so may be preferable for video. Note: a few newer Canon lenses are using a hybrid "Nano USM" that's both fast AND quiet/smooth running, so can be used for both. I imagine other manufacturers make faster and slower focusing lenses, too (I KNOW third party lens manufacturers do).

Larger aperture lenses allow AF to work better, simply by allowing more light to reach the AF sensors. On some cameras an f/2.8 or larger aperture lens (for example), also will allow higher performance AF points to fully work. This doesn't mean you have to maintain the max aperture all the time, though. Stopping down doesn't actually occur until the instant of exposure, with modern lenses. (Note: some vintage lenses and really cheap "pre-set" lenses still being sold actually do stop down when set to a smaller aperture, reducing light available for the AF sensors to work with.)

4. Varifocal zoom lenses.... Many zooms today DO NOT maintain focus when zoomed. Parfocal zooms that do maintain focus are more complex and more expensive, but were particularly desirable back in the day when we focused manually. But, thanks to autofocus which can quickly correct focus with varifocal designs, there's been an increase in this type of zoom in recent years. HOWEVER, if you use the wrong focus method, it can be a problem. When using a non-continuous AF mode (Canon One Shot or Nikon: AF-S, for example), you have to consciously refocus after zooming to change focal length... you have to lift off the button activating AF and reapply it. If you don't, the lens remains focused where it was prior to the change in focal length. This can lead to a lot of focus errors

But if you are using a continuous AF mode (Canon AI Servo or Nikon AF-C, for example), the camera can and should automatically correct any loss of focus due to a change in focal length with a varifocal design, correcting the error so quickly that you don't even realize it's occurring.

For best AF results, it's important to know if your zoom is parfocal or varifocal, to be able to choose an appropriate focusing technique. If you aren't sure and can't find out from the manufacturer's specifications, it's easy to check with a few test shots. (Note: some lenses are partially vairfocal... For example, may maintain focus on more distant subjects, but not when focused closely. So if you test your lens, be sure to do so at various focus distances.)

5. Sounds like a continuous form of AF would be best to use, doesn't it? Well... unfortunately it's not always. For example, if using it with a single point or even a small multi-point setup along with a "focus and recompose" technique, it can and will mess up focus very easily. The trick to allow a continuous form of focus to be used in a wider range of situations is Back Button Focusing. This separates the control of focus from the shutter release button and gives you option to start and stop AF independently. With BBF, which is a popular sports photographer technique, it's possible to use continuous focus as your default mode. For example, to "focus and recompose" with BBF, simply stop focus before re-composing. Most modern DSLR I'm aware of can be set up to do BBF. On all modern Canon with and AF On button on the rear, it couldn't be simpler. In fact, it's already mostly set up... all you need to do is "unassign" focus from the shutter release button.

Many cameras today have fairly complex and "tune-able" AF systems (Canon 7D Mark II has a 500+ page user manual... plus a separate 50 page manual just for the AF system). Especially with more advanced, pro-oriented models it can take some effort to learn how the AF system works how to use it well.