Autofocus tracking speed expectations

The Lazy Destroyer

I've been doing a few motorsports events and have consistently been having focus issues due to lag when shooting subjects moving towards the camera. My keeper rate when shooting like this is pretty bad, a fraction of my usual keeper rate.
I am just now kinda running into this now that I am using a 300mm lens (previously only a 70-200) so now I can get into positions to get oncoming subjects, without risking my life

I am just now realizing that I'm goofing up having exposure NR turned on as this limits the frame rate, and maybe also the focus speed as well (not totally sure). I'll set this to OFF for the next go around to see if results are any different.

What it appears to me after going through quite a few images is the AI Servo maybe hits the subject when a half-press the shutter button. I usually hesitate a little so that the IS can straighten out, then fire at high-continuous. The first image will be soft focused. The next will be softer (bad focus). The next will be more out of focus. Basically what I am seeing is the focus consistently gets worse when the subject it coming towards me. But I think the focus is moving with the subject... just slower than the subject so the focus gets progressively worse.

If I change angles so the rate at which the subject approaches is not as aggressive... it hits fine and tracks fine.

This got me thinking that maybe... duh... there is a limit to how fast my camera/lens combo can track the subject. I guess this makes sense.
If a toy around with the lens, I can point it towards the ground and then out to trees in the distance, it seems to be able to go from macro-side to infinity-side pretty quick.
But maybe when tracking actual motion... there is a limit to how fast it can work.
FYI I am pretty close to subjects regarding the composition, these are not "distant" stuff.

I've tried searching about AI-based focus speed but I am not getting the results for my particular case... regarding the speed of a subject moving towards/away from the camera. I get results on how to get the camera to get into focus faster, which isn't what I mean by focus/tracking speed.

I do see how newer Canon camera bodies have more Custom Functions regarding focus, that appear would maybe help me. Things like AF tracking sensitivity, if I am remembering right. So maybe I am just running into a limitation of my older bodies.

More info:
Lens: Canon 300mm F/4L IS
Body: Canon 40D (I also have a 30D backup)
When shooting oncoming stuff I have lately been at f5.6 but might be anywhere from f4-f6.1, always aperture priority. Sometimes I'm lazy and leave it in shutter priority from panning and just bump it up, but usually AV when doing oncoming.
High-speed continuous and focusing with AI Servo, single point. I've tried the setting where the camera figures best focus point and results were worse (same as before but with erratic original focus point in the set).

I can usually always see how the initial half-press gets it in focus and it gets worse in the viewfinder. The ones that typically keep the whole set in focus I think are just the slower subjects.

I can post up the 40D custom functions if needed, there didn't seem to be a whole lot that would help tracking speed.

Is it possible I am just at the limit for tracking speed for my setup, or is there anything that can be done to speed this up? I'm always trying to get different angles and getting more keepers for shots like this would be nice.

The Lazy Destroyer

I have also read some posts about using the back-button AF and how it can work faster. Maybe not in terms of tracking speed but that it is faster/better than the usual half-press.
I'm going to try this next outing, although I am not sure exactly why separating the focus and metering to separate buttons really would make anything faster.

Better in terms of being able to check metering without setting off the IS, I can see that as being useful. But is it really faster in any way to use that method? If so, why?

ziggy53

I still have a Canon 40D body. I can tell you that, while the Single-Shot AF mode with center focus dot only works pretty well for fast moving subjects, Continuous Tracking/AI-Servo mode is often not up to the task, IMO. If you stay with the 40D I suggest that best results I had for Continuous mode started capture in the center region of the scene, then purposely panning faster than the action to recompose the shot during a short sequence. Take lots of images to improve the number of "keepers". Panning action is much prefered to straight towards (closing) or straight away (receding) subject matter, but when the subject tracks away from you is better because the (negative, in this case) closing rate is "decreasing" (assuming a constant velocity). When the subject is closing on you the closing rate is constantly "increasing" with the decreasing distance; a much more difficult task for predictive AF / AI Servo (unless the subject is braking).

By the way, if you are truly using "AI Focus" mode, that's not the same as AI Servo mode, which is what I recommend for sports-action. AI Focus mode tries to have the camera decide between AI Servo and One-Shot mode, which takes processor time to do and it often selects the wrong mode. Stay in AI-Servo mode for sports-action, as that is the true "predictive AF" mode.

---

I suggest a Canon 1D series body for best sports-action tracking ability. In good light, I still prefer one of my 1D Mark II bodies with a sports lens. (Your Canon 300mm F/4L IS definitely qualifies as a sports lens.)

The Lazy Destroyer

Oops, I use AI Servo. That's what I meant, I forgot there is a mode called "AI Focus" which I don't use. Sorry for the confusion. I edited the original post to be a little more clear.

Ya, the 40D (and 30D) seem to have no problem when panning has the subject approaching or receding just slightly. And subjects traveling away (receding) usually don't have much of a problem, albeit some. It's the oncoming I'd like to try to get a better keeper rate with. At the moment it's mostly just random shots that get in focus.

I'm also a little hesitant to try the back button AF (if it even matters for this particular case) because my 30D does not have it and I really do not want to mix/match shooting configurations between two bodies. I have a hard enough time going back and forth between the 40D monopod setup and hand-holding the 30D when both are panning

kdog

Sounds like you've outgrown your 40D. Used 7Ds are going for a song now that the 7DMKII is out. That would be much better than your 40D. You should be able to pick one for around $600. The 7DMKII if you can swing it has absolutely stellar servo AF.

f/2.8


And yes, back-button focus rules for servo AF!

jmphotocraft

A few thoughts.

Use center point only.

Don't use a UV filter, polarizer, or any other filter. They can affect AF. I experienced this with my 40D, 70-200/4LIS, and a nice B+W UV filter.

Pretty darn sure back button AF does not improve the performance of the AF system itself, but you may find it easier to use than holding the shutter button down halfway.

Track the subject with the AF for a second or two before taking pictures.

If you're thinking of upgrading your camera, I wouldn't bother with the 7D. Some were fine, some had poor AF. I sent mine to Canon for calibration and they confirmed it was off. They adjusted it and made an improvement but it still didn't live up to the hype, IMO. The 70D has the same AF. If a 7D2 is out of the question, I'd look for a lightly used 1D Mark III.

jhefti

Not sure the 40D has this option, but I know on newer Canon models there's the option to set the focus priority in burst mode. What you're describing sounds like you're getting decent focus on the first shot, then the camera is progressively losing focus in subsequent shots in burst mode. At least on the 1D-series bodies one can choose either focus priority (the camera won't take the shot unless it is in focus) or shutter priority (in which case the camera just shoots away). I always have mine set to focus priority as I have no use for soft or OOF shots. Again, not sure the 40D has this option.

Also, for motor sports I should think that you can do a series of single shots (but still in AI Servo mode) and get a better take. I tend not to use burst mode unless the action is really too fast and chaotic to capture by timing alone. That said, I've never shot motor sports so I really have no idea what your needs are.

The Lazy Destroyer

^Thanks for the tips!
I'll try without a UV filter. I think I have a Hoya UV on the 300mm now.
Also one on my 70-200 f4L

With the hoods on those lenses I guess it's not critical to have one. At least to try it out.

I'm almost always in Center AF (unless I'm composing so I need another single-point off to the side), I had tried letting the camera decide but results were... horrible. 40D cannot figure out moving subjects in my case, even when the subject covered all AF points. Center works fine, tho, for the most part.

jmphotocraft wrote: »

If you're thinking of upgrading your camera, I wouldn't bother with the 7D. Some were fine, some had poor AF. I sent mine to Canon for calibration and they confirmed it was off. They adjusted it and made an improvement but it still didn't live up to the hype, IMO. The 70D has the same AF. If a 7D2 is out of the question, I'd look for a lightly used 1D Mark III.

That's a bummer. The original 7D was what I am thinking of picking up. Especially because their used prices are pretty affordable, and I live close by to KEH.

I'd really like the 7D-MKII but it's price is a bit tough for me. Especially because this is just a side gig and still a very new one at that. The 30D/40D actually work fine for what I do, but AF and the ISO range have had me wanting more. I can live with it, but better AF/ISO would be nice

But overall I am pleased with what I have. Which is probably why I have a little sticker shock since the cheap ol' 30D and 40D do so well.

The Lazy Destroyer

jhefti wrote: »

Not sure the 40D has this option, but I know on newer Canon models there's the option to set the focus priority in burst mode. What you're describing sounds like you're getting decent focus on the first shot, then the camera is progressively losing focus in subsequent shots in burst mode. At least on the 1D-series bodies one can choose either focus priority (the camera won't take the shot unless it is in focus) or shutter priority (in which case the camera just shoots away). I always have mine set to focus priority as I have no use for soft or OOF shots. Again, not sure the 40D has this option.

Also, for motor sports I should think that you can do a series of single shots (but still in AI Servo mode) and get a better take. I tend not to use burst mode unless the action is really too fast and chaotic to capture by timing alone. That said, I've never shot motor sports so I really have no idea what your needs are.

I saw references to that setting online and got excited thinking maybe this was my problem, but it's not in the 40D manual so I think it's on the newer bodies, or the 1Dx bodies.

The Lazy Destroyer

Well I went ahead and gave the 7D (original) a go. I got an offer I couldn't refuse.
I wanted to hold out for a 7D Mk2 but the price is just a bit much for me at the moment.
I'll see how the 7D fares over the 40D, just toying around with it seems to be a solid performer, lots of features I'm not used to.

ziggy53

The Lazy Destroyer wrote: »

Well I went ahead and gave the 7D (original) a go. I got an offer I couldn't refuse.
I wanted to hold out for a 7D Mk2 but the price is just a bit much for me at the moment.
I'll see how the 7D fares over the 40D, just toying around with it seems to be a solid performer, lots of features I'm not used to.

I strongly suggest reading the following thread and taking Diana Porter's advise to set up the camera:

http://www.sportsshooter.com/message_display.html?tid=34832

The Lazy Destroyer

^Thanks!

mercphoto

How is it working for you?

The Lazy Destroyer

mercphoto wrote: »

How is it working for you?

The tracking sensitivity seems much better on the 7D compared to the 30D/40D from before. For sure for oncoming subjects. When tracking objects going away, it still takes about a second to really reel in the AF which is about par for the 30D/40D too. For now I am using the settings recommended by Diana Porter which seem to work well enough. With these I can momentarily miss a subject or have a small object get in the way during panning and it will stick w/ the original focus point.

When I originally posted this thread I hadn't realized the built in noise reduction would kill the framerate speeds and since turning it off, I've had to re-learn using the Continuous (High) setting as it is night/day difference in speeds.
And going from the (neutered w/ noise reduction) 40D's ~4fps to the 7D's full 8fps feels crazy fast.
But since then I'm getting better at it.

Not that I was expecting anything different, but I can confirm that image quality comparing the 40D and the 7D are about the same roughly.

I see occasionally references to how the 7DMkII is a huge leap from the 7D, so I can only imagine how good a MkII must be. I'm happy w/ the 7D for now, for the price it's a pretty strong body I think, especially at 1/3 of the price of a new MkII.

My only complaint on the 7D compared to the 40D is the image size, the 18mp pics are a little overkill for what I need and I already miss the days of uploading thousands of the 40D's images because they went so much faster.

pathfinder

While I agree with most of the recommendations for autofocus settings with the 7D, I found that for birds in flight I preferred a group of three AF points seemed to acquire focus lock faster than a single AF point. I do strongly prefer single AF point usage usually, but for BIFs and fast wildlife shooting, I switch a 7D to groups of three AF points. You can have a center group of four AF points, and four groups of 3 AF points - one group right of center, one group left of center, and 2 groups either above or below center. You might try this suggestion and see if you might agree with me.

When the 7D was delivered to the market, it was head and shoulders better than the 40D or 50D at fast and precise AF. For noise reduction, use NoiswWare later and avoid in camera NR like the plague.

The 7DMkii is significantly better still, but in good hands, a 7D can still do a pretty bang up job.