Is AI servo overrated or just my technic...

[Galaxy99]

AI servo should be the best friend of shooting moving subjects. However Ai servo with CF 4-1 setting seldom gives me perfect focus... I use it with all my lens in my signatures, the successful sharp focus ratio is about 20-30%... :(

That's what I usually do. on AI servo, press * the focus on moving subject, keep it pressed while it's moving, click on shutter button to take picture while * is still pressed. Then it give me about 20% good focus pix only.

Did I do something wrong or AI Servo doesn't have that much good AI on my camera???:rolleyes:

[J Rabin]

What the heck is wrong with 20-30% in-focus rate?
What the heck are you complaining about? Your technique? Or that you are attempting capture of subjects exceeding combined lens-body tracking ability?
What are you trying to photograph, under what ambient light EV level, what is its contrast, is it moving toward away or across frame, and are you FIRST aquiring target subject with center focus point?
Have taken the time to read EOS Camera body Sticky "Getting the Most from your 1-Series Camera" .pdf file? The principals apply to consumer bodies also.

You can turn off auto focus, pre-focus on a point where you anticipate the action moving to, and waiting for the moment, if you intimately know the event.
Jack

[sandpiper]

The AF gets better and more accurate as you move up through the range of camera models. I find my 20D struggles in AI servo with some fast moving targets as the focusing cannot keep up, so in those cases I would get a similarly low rate of sharp shots. When in such a situation I used to use either one shot AF or MF (prefocusing on a point and shooting when the subject reaches it).

The 5D is a world apart, much better AF and AI servo keeps up with fast moving targets and gives a high ratio of sharp shots.

A 1D would perform even better and probably rarely miss focus except in very extreme conditions.

If the technique you are using isn't working, it's a matter of trying another technique until you find the best way to shoot that suits your cameras capabilities.

I presume that the lack of sharpness is down to missed focus and not simply motion blur, caused by poor panning technique or too slow a shutter speed ?

[mspringfield]

I have never shot with a 400D but 20-30% sounds pretty good for that particular body. There are lots of things that will effect that percentage. Technique, subject speed, subject direction (it is much more difficult to track a subject moving toward you at an angle), lens speed, and even battery life (tracking will slow down as batter life gets low). I am not sure about the 400 but the 1 series has an AI speed setting that effects how quickly it refocuses if something moves in front of the lens.

[GyRob]

What are you photographing ? and are you using center focus point only ?
you need to give a bit more info .
Rob

[liza]

What shutter speed do you typically use? That can impact the quality of a sports shot. And your keeper rate will improve as you practice. I've been shooting for years and am probably only at around 70 to 80%.

[steved110]

I found that AI servo focus on my 20D was disappointing - it struggled to get pin-sharp on galloping horses - but also I feel there was probably some user error too - perhaps camera shake, I'm not 100% sure.

i haven't tried it often enough to form an opinion, but i get the impression from other people's posts that it is not an uncommon thing to feel a prosumer camera can't keep up, whereas a 1-series could.

[Galaxy99]

Thanks guys. I shot for varies sports like soccer, volleyball and track and field. I am often struggled that when I captured a great action, but it turned out to be a slightly or complete OOF with AI servo....

I usually shoot sports with different lens in my signatures, I usually get about 1/1000 to 1/3200 shutter speed. My aperture usually set at 1.8-2.8. I assume slightly camera shake should NOT be a fact on focusing here. I hope the technique I posted on my original was correct with Ai Servo. I really like to improve the good focused picture percentage of my shoots.

I did read the article, J Rabin. I followed the basic technique. Both my 400D body doesn't have that much setting like 1D body. I didn't know why you sound angry about my post. (I wish you are NOT a canon share holder or employee, if so, I am sorry). If you think 20-30% on good focus is good enough with Ai servo, I have very good reason to be disappointed on this function from Canon. But I believe lots of photographers here have much higher successful ratio on sports with or without Ai servo. That's what I try to learn from. Thank you.

[J Rabin]

Nah, not angry at all.
Just some crass humor! I'll have to be more careful with "written" sarcastic humor on Forum chat. Sorry. The other party can't see smile on my face when they complain of 20-30% keeper rate. That's not bad, even for a pro.

Anyway, the 400D does have a f/2.8 precision center focus point.
Practice on something easy to start. In bright daylight, leave camera on auto FP selection, AI Servo, pick a contrasty subject moving toward you. "Acquire" the subject 1st with the Center FP, even if it later moves out of center frame, because that's the way AI Servo works.
A 400D should be able to track a subject moving fairly quickly. I just go to the velodrome when I want to practice "follow focus:"
http://aesop.rutgers.edu/~rabin/Personal/TTown_Lehigh_Velo/Charles_C/slides/CharlesC_T-Town_01.htm
http://aesop.rutgers.edu/~rabin/Personal/TTown_Lehigh_Velo/slides/Daylight_Action.htm

With soccer or volleyball, you may have to leave the camera in Center FP because other players cross into the frame and pull the focus off. It's harder.

Part of your problem may be the extremely shallow depth of field shooting wide open. If you are under 10 meters from a subject, shooting at f/1.8 to f/2.8, you depth of field is very thin. Out of focus shots with such narrow DoF are within the "focus accuracy specification" of the camera. Try running the camera at f/5 or f/5.6, and compromise a bit on shutter speed or raise ISO. If you get more keepers that way, then the narrow DoF is source of your low keeper rate.
Here, at f/9 and 1/640, the DoF is still thin at long focal length: http://aesop.rutgers.edu/~rabin/Personal/Canon_70_300_DO_IS/slides/05_Fast_Focus.htm
Here at f/5 and 300mm, you can see how shallow the DoF is on the road: http://aesop.rutgers.edu/~rabin/Personal/Tour_Somerville_2006/slides/300f4IS_Somerville_f5.htm. I just manually focused and waited for the sprint.

Sorry for the earlier sarcastic humor.....
Jack

[superdiver]

I shoot alot of sports and a 20-30% focus rate would not be bad in my book either...You have to remember these things are happening very fast. I am not sure that a 1DMkII would get a you a much higher rate and it has VERY quick auto focus...

[Galaxy99]

Thanks for the tip, Rabin. Your pictures look very very sharp. Those pix are the ones I like to kill me self to get...;) Sorry, i wasn't able to pick up the humor at first place. I thought I offended a Canon employee here...:)

I assume if I use Center FP on AI Servo mode, I should always cover the moving object with the Center FP while she/he moves right, don't I? For a person, I don't know if you should use Center FP to cover his/her body (check level) or use top FP to cover his/her face if I like to see the face expression... sometimes, face and body are just not in the same frame in some sports....

[Tandem]

A lot of my slightly out of focus shots are due to bad timing on my part. Remember it is focus... wait for focus lock ... click shutter. The wait period varies with camera, lens, subject contrast and lighting conditions. At night games with black uniforms the wait for focus can be a long time. My shots are much better at the start of a game and towards the end of a long shoot I tend to get lazy and snap the photo too soon. Sometimes when you try for a quick shot like a keeper's reaction to a shot on goal you just have to move quick and hope your timing is spot on.

Another reason for slightly out of focus shots is when the player holds a hand, stick, or ball out in front of them and that is where the focus locks in on.

Badly out of focus shots happen when I miss the player alltogether. Usually it is easy for me to figure out what I focused on.

[Tandem]

I assume if I use Center FP on AI Servo mode, I should always cover the moving object with the Center FP while she/he moves right, don't I? For a person, I don't know if you should use Center FP to cover his/her body (check level) or use top FP to cover his/her face if I like to see the face expression... sometimes, face and body are just not in the same frame in some sports....
Some folks might be able to focus in on the face but I'm not good enough to do it for fast moving sports. I usually try for the chest area and hope for the best. At least 90% of my photos end up being cropped to get the player positioned right.

[Jon, The Elder]

Double your practice and technique time. No matter what your gear, you will bring your 'keeper' rate up proportionally, guaranteed.

[Dan-o]

On my XT it was pretty bad. I'm very happy with it on my 30.

[superdiver]

Agree with you, Dan-O 100%!