So I'm migrating from my 1D Mark 3 to a 7D and one difference is the additional option of AI Focus (the mark 3 only has one shot and AI servo).

I'm looking for any downside to using AI Focus rather than AI Servo - the way the manual describes it AI Focus is the best of both worlds (see attached). With an added bonus of the focus confirmation!

However, my concern is regarding sports shooting ONLY- Anyone with direct experience with this type of scenario that can share some insight as to the results they get with AI Focus while shooting sports (preferably outdoor daytime sports like football or soccer) that involve tracking people while in motion.


Thanks in advance!

-rich56k

I wouldn't use AI Focus. It takes extra time for it to figure out which mode to use, this in turn can cost you shots. Either use One Shot or AI Servo as required for your particular needs.

Originally Posted by rwells I wouldn't use AI Focus. It takes extra time for it to figure out which mode to use, this in turn can cost you shots. Either use One Shot or AI Servo as required for your particular needs.

Thanks Randy, I was thinking about that same issue.

I should have added that when I shoot sports I'm always tracking the object (person, motorcycle, etc) before I actually shoot. Wouldn't that put me in servo mode already?

Hence my confusion - any 7D shooters care to chime in ?

Ideally with keeper rates using both options in action sports events.

Ironically I almost never missed an action shot(s) with my 20D, albeit fewer frames per second but my keeper rate was way better than the 7D so far.

-rich56k

Originally Posted by rich56k ... I should have added that when I shoot sports I'm always tracking the object (person, motorcycle, etc) before I actually shoot. Wouldn't that put me in servo mode already? ...

AI Focus allows the camera to choose between AI Servo and One Shot modes. Unfortunately, AI Focus often makes the wrong choice and increases the likelihood for focus error.

If you really need to rapidly switch between AI Servo and One Shot modes, assign a button to toggle modes so that "you" are in control of which focus mode is active. (The DOF Preview button can be programmed to toggle AF modes, for instance.)

It is recommended to use the back button labelled, "AF-ON " to start AF. You do have to hold the button during AI Servo acquisition and lock. (Note that the AF-ON button may need to be turned on with C.Fn.IV-1)

Do remember that AI Servo mode takes a little time to sample and calculate subject motion. Remember too that the 7D autofocus slows acquisition in lower light. Proper anticipation is the key to 7D AF success in AI Servo mode.

Originally Posted by rwells I wouldn't use AI Focus. It takes extra time for it to figure out which mode to use, this in turn can cost you shots. Either use One Shot or AI Servo as required for your particular needs.

Like Randy, I never use AI focus.

Don't forget that there are 4 buttons around the rim of long L glass that switch between One Shot and AI servo as well

Originally Posted by ziggy53 It is recommended to use the back button labelled, "AF-ON " to start AF. You do have to hold the button during AI Servo acquisition and lock. (Note that the AF-ON button may need to be turned on with C.Fn.IV-1) Do remember that AI Servo mode takes a little time to sample and calculate subject motion. Remember too that the 7D autofocus slows acquisition in lower light. Proper anticipation is the key to 7D AF success in AI Servo mode.

First off, thanks to all of you (Randy, Pathfinder and Ziggy) for your replies!

Per your suggestions I've set up both the DOF button to switch the AF modes, and the AF-ON to start AF ... however, as I have a stunt riding event this afternoon I want to ask is there any downside to leaving the shutter button with the same function as I'm used to tracking via holding the shutter down 1/2 way and this way as I relearn using the AF-ON I will inadvertently not use it everytime as things get pretty fast paced at times and I'm sure by instinct I will continue to use shutter only at times.

Lastly your comment about the low light 7D AF performance leads to another Q... the event wraps Sat eve at 10 p.m. which means approx 2 hours in very bad light - they will have generator lighting but its not the best ...would you go for the proven AF on the Mark 3, albeit with poor ISO range/performance or 7D due to its high ISO range?

Note: I'll be using a 70-200 2.8 nonIS for this event.

Thanks again for your suggestions!

-rich56k

Originally Posted by rich56k ... is there any downside to leaving the shutter button with the same function as I'm used to tracking via holding the shutter down 1/2 way and this way as I relearn using the AF-ON I will inadvertently not use it everytime as things get pretty fast paced at times and I'm sure by instinct I will continue to use shutter only at times. Lastly your comment about the low light 7D AF performance leads to another Q... the event wraps Sat eve at 10 p.m. which means approx 2 hours in very bad light - they will have generator lighting but its not the best ...would you go for the proven AF on the Mark 3, albeit with poor ISO range/performance or 7D due to its high ISO range? Note: I'll be using a 70-200 2.8 nonIS for this event. ...

I'm not aware of any problems using the half-shutter plus the back focus button. By all means, use what is comfortable until you practice and confirm the new technique.

Some folks did have issues with spectral highlights in the background interfering with the 1D MKIII autofocus, while others noticed no problems at all. I suggest that if have that situation when the sun goes down, switch to the 7D. Otherwise, I would trust the 1D MKIII myself.

Not so sure about the 1D MKIII being a poor performer in high-ISO conditions. Compared to the 7D they are probably fairly similar. Both cameras do not tolerate under-exposure, so watch your RGB histogram to make sure that your subject is properly exposed. Try not to blow out important highlights, but otherwise shoot "to the right".

When you can, do some testing with intermediate ISO settings. Some bodies have definite random sensor noise improvement with multiples of ISO 160.

http://photo.net/canon-eos-digital-camera-forum/00Yita

Originally Posted by ziggy53 I'm not aware of any problems using the half-shutter plus the back focus button. By all means, use what is comfortable until you practice and confirm the new technique. Some folks did have issues with spectral highlights in the background interfering with the 1D MKIII autofocus, while others noticed no problems at all. I suggest that if have that situation when the sun goes down, switch to the 7D. Otherwise, I would trust the 1D MKIII myself. Not so sure about the 1D MKIII being a poor performer in high-ISO conditions. Compared to the 7D they are probably fairly similar. Both cameras do not tolerate under-exposure, so watch your RGB histogram to make sure that your subject is properly exposed. Try not to blow out important highlights, but otherwise shoot "to the right". When you can, do some testing with intermediate ISO settings. Some bodies have definite random sensor noise improvement with multiples of ISO 160.

Thanks again for your reply/info!

I'll give it a go (actually in about 3 hrs.) with the 7D and be able to go thru everything tonight. That will provide the opportunity to adjust my settings for tomorrow if needed.

I should have worded the MarkIII/7D ISO comment differently, I've always had good results so far using the MarkIII, then the 7D comes out with it's higher range of ISO and one tends to get all excited.

So with confidence levels boosted, I'm off to the races (literally!)

Thanks again Ziggy!

I'll post back tomorrow with my experience.

-rich56k

as I'm used to tracking via holding the shutter down 1/2 way and this way as I relearn using the AF-ON I will inadvertently not use it everytime

I have to admit that I forgot to use the back button a few times after I switched, but it becomes habit quickly enough, and it is much better for a number of reasons. One is that if you have lenses with full time manual focusing, you can forget about switching your lenses to MF. When you want to focus manually, just don't push the back button. And you can do any setup you want without worrying about the shutter inadvertently activating AF again when you don't want it.

Update - overall I'm pretty pleased with the results:

1416 total shots
866 keepers (tack sharp)
270 publication quality

The difference being the tack sharp category was for me to get an accurate account of the AF performance - tack sharp, but not pics that I would submit to pubs for consideration due to composition, background, ect.

To be honest after shooting Junior College Football and Soccer the results were so bad I figured I'd only be able to use the 7D for feature bike shoots (stationary motorcycles) outdoors. I wasn't confident enough in the results to even want to try any more event work.

That has changed as of today, I can relegate the Mark III to backup camera (yes I'm getting too old and lazy to lug that tank around for 5-8 hours in the hot sun).

Thanks again for the suggestions!

-rich56k

Just for clarity... For these shots did you used AI-Servo and didn't use AI-Focus, right?

Thanks

Originally Posted by rich56k Update - overall I'm pretty pleased with the results: 1416 total shots 866 keepers (tack sharp) 270 publication quality The difference being the tack sharp category was for me to get an accurate account of the AF performance - tack sharp, but not pics that I would submit to pubs for consideration due to composition, background, ect. To be honest after shooting Junior College Football and Soccer the results were so bad I figured I'd only be able to use the 7D for feature bike shoots (stationary motorcycles) outdoors. I wasn't confident enough in the results to even want to try any more event work. That has changed as of today, I can relegate the Mark III to backup camera (yes I'm getting too old and lazy to lug that tank around for 5-8 hours in the hot sun). Thanks again for the suggestions! -rich56k

Originally Posted by Dan7312 Just for clarity... For these shots did you used AI-Servo and didn't use AI-Focus, right? Thanks

Yes, that's correct AI Servo only yesterday, in the past I had been using AI Focus exclusively.

-rich56k

Some great videos from Canon here on the AF system of the 7D and other information. Quite informative. I like the Zone AF in AI servo for wildlife shooting, especailly in low light when single point AF begins to fail.

http://www.learn.usa.canon.com/galle...utorials.shtml

For those trying to use AI Focus.
The camera manuals seem to be very misleading and have bad translations into English.
As for AI Focus it should read as follows.
This mode will automatically select either One Shot Focus or AI Servo when the shutter button is pressed halfway and stay on that mode of focus.
If the subject is moving when the shutter button is pressed and held,then it will select AI Servo and stay on that, even if the subject after that stops moving.
If the subject is stationary when the shutter button is pressed, it will select One Shot Focus and stay locked on that even if the subject after that starts moving.
I am yet to find a canon camera to operate as the manual explains it, some people may think it works , but I doubt that.
This function selects but does not change from one mode to another, Canon keep very quite on this subject.
It works very well as a automatic selector but forget about auto changeover as stated in the manual.
I really hope I am totally, totally wrong and all our cameras start working form now as the manual tells us, just to prove me wrong,that would be great.
Hope this is some help.

So there seems to be a lot of mentions in other places about the 7D having a lot of focusing issues. How correct is that?

Originally Posted by sneaky77 So there seems to be a lot of mentions in other places about the 7D having a lot of focusing issues. How correct is that?

I believe that the AF section of the Canon 7D is one of Canon's better AF implementations. I believe that it compares well to the top-of-the-line 1D series in good light, but it slows in low light. (This behavior is documented somewhat in the user manual on the bottom of page 93.)

AF speed and accuracy are excellent when the 7D is used in conjunction with a flash with an AF Assist light at a suitable distance.

Many people misuse the AF MicroAdjust capabilities of modern cameras with that capability. I believe that when that happens, the users often blame the camera. This also applies to the 7D.

Many people misunderstand when and how to use AI Servo mode versus One-Shot mode and many people also misunderstand "how" to make best use of AI Servo (i.e. they use the wrong technique).

The Canon 7D is extremely flexible concerning setup and many folks just don't take the time to explore appropriate settings for different situations.

Used correctly, I believe that the Canon 7D AF is very fast and accurate. Used incorrectly, and/or used with poor technique, and it will fail as can be expected.

Originally Posted by ziggy53 I believe that the AF section of the Canon 7D is one of Canon's better AF implementations. I believe that it compares well to the top-of-the-line 1D series in good light, but it slows in low light. (This behavior is documented somewhat in the user manual on the bottom of page 93.) AF speed and accuracy are excellent when the 7D is used in conjunction with a flash with an AF Assist light at a suitable distance. Many people misuse the AF MicroAdjust capabilities of modern cameras with that capability. I believe that when that happens, the users often blame the camera. This also applies to the 7D. Many people misunderstand when and how to use AI Servo mode versus One-Shot mode and many people also misunderstand "how" to make best use of AI Servo (i.e. they use the wrong technique). The Canon 7D is extremely flexible concerning setup and many folks just don't take the time to explore appropriate settings for different situations. Used correctly, I believe that the Canon 7D AF is very fast and accurate. Used incorrectly, and/or used with poor technique, and it will fail as can be expected.

I agree, AI servo works best for moving subjects
tips on 7D sports /action settings -
http://www.sportsshooter.com/message...html?tid=34832