EOS 550D AF points

[HalAdams]

I am spending some time getting to know all the ins and outs of the camera.

The first thing that puzzles me are the AF points. I cannot yet see why there are so many - surely just one point [in the middle] is all that is needed? I'd be interested in a plain english explanation of this one!

My question: Is there any way to cancel out all the peripheral AF points and leave just the centre one as a default for all programs? Unless I am missing something, the default seems to be all the AF points on...

 

[Didereaux]

I am spending some time getting to know all the ins and outs of the camera.

The first thing that puzzles me are the AF points. I cannot yet see why there are so many - surely just one point [in the middle] is all that is needed? I'd be interested in a plain english explanation of this one!

My question: Is there any way to cancel out all the peripheral AF points and leave just the centre one as a default for all programs? Unless I am missing something, the default seems to be all the AF points on...

Okay, somebody has got to say it: READ THE F'ing Manual!!!!!!!!!!!!!! don't have a paper one, download it.

 

[CameraClicker]

Sometimes the manual tells how to make a feature work but why you would want that feature is not so clear. The 550D actually has very few AF points, it is a weak feature. You should look through the viewfinder of a 1Dx! Anyway, you are correct, the middle AF point in a 550D and many other models is the only cross type AF point, and that makes it most powerful. Once you have selected a single AF point, that point will be the one that remains, even through a battery change, until you select a different point, or all points again. At least this is the case if you use Creative Modes: M, Av, Tv, and P. M, Av and P are the only modes I have ever used with that body, so I can't comment on what the green square and those others do. Since they set almost all options, they may affect AF points too.

When you have time to focus and recompose, the single centre AF point is a great option. Times when you can't use that point for one reason or another, the others are there to help out. Not everyone shoots only portraits or landscapes. Even shooting portraits, since you want at least one eye sharp, and you might be shooting with the lens open to f/1.2 or f/1.4, with a razor thin depth of field, recomposing may cause you to lean forward or back slightly. Just enough to throw off focus. Set the point where the eye is, focus and shoot. No recompose, quick operation between focus and shutter release, less chance of missing focus.

The manual says there are 3 focus modes. One Shot and Servo are the useful ones. One Shot for stationary and slow moving subjects, Servo for faster subjects moving toward or away from you. Servo tracks your subject, predicting where your subject will be an instant later. So, it is useful for shots like this one from Stanley Park's aquarium
https://www.flickr.com/photos/54048679@N07/9690241442/
But there is a catch. Since the camera is tracking your subject, you have to keep the focus point on your subject. That can be a challenge when your subject is fast! And you may not want your subject in the bull's eye. So, again the other points are useful. Turn them all on and your subject can be anywhere near the centre, instead of exactly at the centre. This helps a lot when trying to track your subject and it is moving around in the viewfinder. With practice you can get your subject on the point you want to use, and you can move the points around fairly quickly to use a single point if desired.

The benefits will become clearer once you start shooting.

 

[HalAdams]

Okay, somebody has got to say it: READ THE F'ing Manual!!!!!!!!!!!!!! don't have a paper one, download it.[/QUOTE]

Thanks! I'd hate to see your reply to a lesser question...

CameraClicker, yes, you have identified my point exactly - why all the, albeit few, AF points?! I hope as I progress along, it will become clearer. I take your point that some will be taking more artistic shots where a subject on the edge may well be the main target and yes, an off-centre point will be most useful.
Now, interesting in what you say - I am using the 'green frame' (the fully auto function) as my starter and it is this that has the default of all the points 'on'! So, I shall go out tonight and experiment in all the other modes, and if the setting remains throughout, then I am happy (the manual is not clear on this point). The green square is for snapshots and yes, I guess it is right for Canon to have all the features on.
I like your second pargaraph, but am a far way off focussing and recomposing! As for your last paragraph - maybe we can re-visit in some years to come...if I could ever get a clear focus on something coming towards me, then my application to join National Geographic will be in the post!!

 

[HalAdams]

Sometimes the manual tells how to make a feature work but why you would want that feature is not so clear. The 550D actually has very few AF points, it is a weak feature. You should look through the viewfinder of a 1Dx! Anyway, you are correct, the middle AF point in a 550D and many other models is the only cross type AF point, and that makes it most powerful. Once you have selected a single AF point, that point will be the one that remains, even through a battery change, until you select a different point, or all points again. At least this is the case if you use Creative Modes: M, Av, Tv, and P. M, Av and P are the only modes I have ever used with that body, so I can't comment on what the green square and those others do. Since they set almost all options, they may affect AF points too.

When you have time to focus and recompose, the single centre AF point is a great option. Times when you can't use that point for one reason or another, the others are there to help out. Not everyone shoots only portraits or landscapes. Even shooting portraits, since you want at least one eye sharp, and you might be shooting with the lens open to f/1.2 or f/1.4, with a razor thin depth of field, recomposing may cause you to lean forward or back slightly. Just enough to throw off focus. Set the point where the eye is, focus and shoot. No recompose, quick operation between focus and shutter release, less chance of missing focus.

The manual says there are 3 focus modes. One Shot and Servo are the useful ones. One Shot for stationary and slow moving subjects, Servo for faster subjects moving toward or away from you. Servo tracks your subject, predicting where your subject will be an instant later. So, it is useful for shots like this one from Stanley Park's aquarium
https://www.flickr.com/photos/54048679@N07/9690241442/
But there is a catch. Since the camera is tracking your subject, you have to keep the focus point on your subject. That can be a challenge when your subject is fast! And you may not want your subject in the bull's eye. So, again the other points are useful. Turn them all on and your subject can be anywhere near the centre, instead of exactly at the centre. This helps a lot when trying to track your subject and it is moving around in the viewfinder. With practice you can get your subject on the point you want to use, and you can move the points around fairly quickly to use a single point if desired.

The benefits will become clearer once you start shooting.

Thanks again - everything a lot clearer with some experimentation following your comments!
You are right - the single AF spot stays programmed throughout, but only on the Aperture, Speed and Manual modes.
I now have a feel for the buttons, so I can now move onto picture composition!