Help With AF Points

VitaminV

I'm hoping to improve my technique when shooting lacrosse. Here's my problem; when I moved from a not so long and not so fast lens to a 70-200 f4, my keeper rate dropped because of out of focus issues. When the focus is on the shot is beautiful with the improved DOF the f4 delivers, but when the focus is off then the shot is really off for the same reason. I used to select center point focus and AF servo, but that had it's problems when the center point would be between two players. Now I let the camera (40D) select the AF points. I'm finding this to be too unpredictable. I'm in bright sunny CA so I can stop down, but it's not the same when a player on the field and someone sitting in the stands across the way are both in focus. I want to stay with the f4 (good thing I can't afford the 2.8 huh?). Any suggestions?

nw scout

The main thing with the auto focus points in to put them on something well lit, and or, something with good contrast. Find a part of the subject that the auto focus can grab hold of and stay on it.
Stay with the single point, it works the best by far!!!

ian408

Moving to cameras for a bit more exposure.

NeilL

AI Servo AF has been reported in DGrin by other people as working very well in the situation you describe. My understanding is that once you achieve initial focus on the subject, the subject must remain continuously tagged by at least one focus point, with the shutter button continuously pressed down half way, until the shot is taken.

Don't understand why you would try for initial focus by pointing the active focus point between two players?

Neil

kdactionphoto

Hey Vit.

I may be wrong but I think you would have better success with AFC. This would be a constant update of your focus point as you hold the shutter 1/2 way down. AFS locks at initail focus of your subject and the shutter 1/2 way down. I shoot with a D300 and use AFC, single and multiple point, depending on distance and surrounding objects.

Kevin

ziggy53

As you have already discovered, the Canon 40D is a little underpowered for tracking action sports. Multiple AF point selection really does slow things down.

Single point AF, and center point at that, and AI-Servo should get you the best that the camera can deliver. I suggest using slightly looser framing so that you can locate the center dot on the principal player that you want to track, and then crop in post for best composition. Multiple AF points quickly overwhelm the processing section of the camera.

An f2.8 version of the lens really is better so for critical games I suggest renting an EF 70-200mm, f2.8L USM because the center focus dot is also more sensitive and more accurate with an f2.8 aperture lens.

Also, anticipate the action and start your AF (half-depress) before you need it. AI-Servo takes a moment to sample and acquire the rate of motion. Shoot in short bursts to increase your total keeper rate. (Even with best technique and best lenses the keeper rate of a 40D is estimated at around 45 percent for rapid action sports.)

A Canon 1D II/IIN/III/IV is a much better choice for this sort of action sport because of the more advanced AF section and dual processors to help with the workload. However, even the best combination of camera and lens and technique and conditions will not yield a 100 percent keeper rate. A 1D series camera with an EF 300mm, f2.8L IS USM might achieve high seventieth to low eightieth percentiles of keepers, for instance, in perfect conditions.

nw scout

ziggy53 wrote:

As you have already discovered, the Canon 40D is a little underpowered for tracking action sports. Multiple AF point selection really does slow things down.

Single point AF, and center point at that, and AI-Servo should get you the best that the camera can deliver. I suggest using slightly looser framing so that you can locate the center dot on the principal player that you want to track, and then crop in post for best composition. Multiple AF points quickly overwhelm the processing section of the camera.

An f2.8 version of the lens really is better so for critical games I suggest renting an EF 70-200mm, f2.8L USM because the center focus dot is also more sensitive and more accurate with an f2.8 aperture lens.

Also, anticipate the action and start your AF (half-depress) before you need it. AI-Servo takes a moment to sample and acquire the rate of motion. Shoot in short bursts to increase your total keeper rate. (Even with best technique and best lenses the keeper rate of a 40D is estimated at around 45 percent for rapid action sports.)

A Canon 1D II/IIN/III/IV is a much better choice for this sort of action sport because of the more advanced AF section and dual processors to help with the workload. However, even the best combination of camera and lens and technique and conditions will not yield a 100 percent keeper rate. A 1D series camera with an EF 300mm, f2.8L IS USM might achieve high seventieth to low eightieth percentiles of keepers, for instance, in perfect conditions.

All good info, but I would stay away from the 1D Mark 3. BIG auto focus problems with that camera.

ian408

nw scout wrote:

All good info, but I would stay away from the 1D Mark 3. BIG auto focus problems with that camera.

With early versions, yes. But with the repaired or newer bodies, not so much. The mkii is still better though.

nw scout

ian408 wrote:

With early versions, yes. But with the repaired or newer bodies, not so much. The mkii is still better though.

The first ones were really really bad. Repaired ones are really bad, and the later models were just bad.
I bought a few and rented many for jobs and always went back to my Mark 2n.
Maybe I was just unlucky, or maybe the Mark 2 is just so good its hard to compare anything to it.

ian408

nw scout wrote:

The first ones were really really bad. Repaired ones are really bad, and the later models were just bad.
I bought a few and rented many for jobs and always went back to my Mark 2n.
Maybe I was just unlucky, or maybe the Mark 2 is just so good its hard to compare anything to it.

I'm happy with my repaired iii. There was a software update that came out around that time that solved some other problems. I do think the 2 (n or not) is still better with respect to focus speed.

GadgetRick

As usual, Ziggy gives awesome advice. I shoot with a 50D and, when I'm shooting sports, I use AI-Servo with center focus. I focus on my subject to lock focus then burst 2-4 shots. The first shot (sometimes will be out of focus) but all others (usually) will be in focus.

ziggy53

ian408 wrote:

I'm happy with my repaired iii. There was a software update that came out around that time that solved some other problems. I do think the 2 (n or not) is still better with respect to focus speed.

Ultimately Vincent Laforet had 3 of the 1D MKIII bodies that I believe he could rely upon. Even Rob Galbraith continues to shoot with Canon, despite his complaints, and he could/would convert to Nikon if he wished and needed to.

One trick that no one talks about is "not" using the AF Micro-Adjustment (AF-MA) for lenses and action which require the fastest responsiveness. The AF-MA seems to take time and sometimes it does not complete during a rapid action sequence using AI-Servo focus, resulting in an additional opportunity for OOF images. i believe that particular problem has been worked out in the 1D MKIV.

VitaminV

Thank you ziggy53

ziggy53 wrote:

As you have already discovered, the Canon 40D is a little underpowered for tracking action sports. Multiple AF point selection really does slow things down.

Single point AF, and center point at that, and AI-Servo should get you the best that the camera can deliver. I suggest using slightly looser framing so that you can locate the center dot on the principal player that you want to track, and then crop in post for best composition. Multiple AF points quickly overwhelm the processing section of the camera.

An f2.8 version of the lens really is better so for critical games I suggest renting an EF 70-200mm, f2.8L USM because the center focus dot is also more sensitive and more accurate with an f2.8 aperture lens.

Also, anticipate the action and start your AF (half-depress) before you need it. AI-Servo takes a moment to sample and acquire the rate of motion. Shoot in short bursts to increase your total keeper rate. (Even with best technique and best lenses the keeper rate of a 40D is estimated at around 45 percent for rapid action sports.)

A Canon 1D II/IIN/III/IV is a much better choice for this sort of action sport because of the more advanced AF section and dual processors to help with the workload. However, even the best combination of camera and lens and technique and conditions will not yield a 100 percent keeper rate. A 1D series camera with an EF 300mm, f2.8L IS USM might achieve high seventieth to low eightieth percentiles of keepers, for instance, in perfect conditions.

Thank you for this most excellent reply. I will get busy with your suggestion of single-point (center) AI-servo technique, and I'll try and resist the urge to shoot too tight.

Friday night we will be under the lights. I'm thinking this might improve AF performance?

Maybe I should clarify my keeper percentage. I'm basing my 10 to 20% on what I consider "post worthy". I'd guess I lose 20% for technical reasons, focus, exposure, etc. The other 60% are technically okay but are just not interesting enough or would require too radical post work to be worth while.

Oh, here's another question for you if you would be so kind; normally with sports I just shoot a Medium JPEG and just crop and sharpen at PP. This last shoot with the 70-200 f4 I used RAW+M-JPEG. Do you think I'm needlessly overburdening my processor? I was thinking when I shoot under the lights I might want the RAW file to correct for WB. Any thought you have on this would be greatly appreciated.

As far as equipment goes, unless I find that box of money, I'll be shooting what I have for a while. Besides I'd like the capacity of my equipment and not my technique to be the limiting factor, and that's a way off right now. Thanks again.

MikeV

ziggy53

For night shooting under "lights" the 40D will definitely suffer. It lacks the AF advancements to reduce the effects of "light strobing" which affect many AF systems. Some of the very latest dSLRs, and especially the latest professional class dSLRs, have AF systems to help detect and compensate for the flicker of many outdoor lighting systems.

I used to shoot just large JPGs and then set up a series of Photoshop actions to help compensate for WB problems that inevitably occur under outdoor lighting. Some folks use RAW but I preferred the smaller file size the JPG files afford. I can easily accept color problems if I manage to capture the more interesting action on the field. Likewise with noise. Use whatever ISO you need to capture the action. Noise is less of a consideration than image interest overall.

If you shoot in short bursts, and shoot lots and lots of images, you should get an acceptable "crop" of images at the end.

Also, feel free to try anything and everything in your quest for a working strategy. In the end it's what works for "you" and the style of shooting that you develop that makes the biggest difference.

VitaminV

Thank again you ziggy53
I did a quick search on 'light strobing' and couldn't come up with anything. If you could point me in the right direction I'd love to research it. I don't believe the 40D has an AF-M option, I'll check into that. Also I know that the 70-200 has a focal range switch which I've heard if is in the incorrect position could slow focus down.

Here are a few shots from Sunday. Your CC is more than welcome. I like 077 but I tipped the horizon and it really needs a tighter crop to get rid of some of the cluttered background.

http://vitaminv.smugmug.com/Lacrosse/PetLax-03212010/11613997_Ev3mb#818695341_mjKaK

ziggy53

VitaminV wrote:

I did a quick search on 'light strobing' and couldn't come up with anything. If you could point me in the right direction I'd love to research it. ...

Read this white paper about the AF systems used in the 50D and 5D MKII, where Canon claims to be using the flicker detection and correction. (Page 32) Specifically:

"Here’s how it works: during Phase Detection AF, the AF engine rapidly measures the density of horizontal and vertical details in a scene and the camera processor uses this data to determine where
the sharpest edges and details are located. When found, the AF is locked on target.

But under fluorescent lighting and some other artificial lighting sources, a rapid, imperceptible
flickering of the light occurs along with sudden color temperature shifts. These tend to throw off the density measurements and therefore the accuracy of the AF calculations. In both the EOS 50D and EOS 5D Mark II, the type of lighting is taken into effect, and readings are averaged and processed with the help of the super-fast DIGIC 4 Image Processor.

The result is improved AF accuracy and speed when shooting under lighting conditions that could fool the AF systems found on earlier Canon and competitive models alike."

http://www.usa.canon.com/uploadedimages/FCK/Image/White%20Papers/EOS%2050D%20and%205D%20Mark%20II%20WP2.pdf

VitaminV wrote:

... I don't believe the 40D has an AF-M option, I'll check into that. Also I know that the 70-200 has a focal range switch which I've heard if is in the incorrect position could slow focus down.

Here are a few shots from Sunday. Your CC is more than welcome. I like 077 but I tipped the horizon and it really needs a tighter crop to get rid of some of the cluttered background.

http://vitaminv.smugmug.com/Lacrosse/PetLax-03212010/11613997_Ev3mb#818695341_mjKaK

I'm not sure that AF-M applies to Canon, so I'm not sure what you're asking. Yes, employing the focus limiter can improve AF speeds, especially if the AF has to "hunt". If you find your AF system hunting with the 70-200mm, f4L, you are probably at, or close to, the limits of the AF system in the lighting circumstances.

GadgetRick

Very nice shots Vit. I might crop one or two but they look good to me.

Ziggy,

You just taught me something about my 50D. I didn't realize they'd improved the AF for this sort of thing. Explains why I find the AF to be quite good in my sports shots. Thanks as always! You're a scholar and a gentleman...

RTM

AF and sports
I've found very good results using back button focusing.

I don't think it has been mentioned yet, but you can sever the focus from the shutter button. This will allow a separate focus button and the shutter does the metering / shutter actuating.

It takes some getting used to, and makes your camera impossible for others to use, but can help with auto-focus and quick action situations:

canon back button auto-focus