Focusing problems using different focus points

When I use the centre focus point on my 10D, focusing is perfect. However when I switch to any of the other focus points, I nearly always get soft images. I find that using the centre point to focus and then recomposing actually works better than using one of the other points, which I would not expect, since I am moving the camera.

Is this a normal occurance because the centre point is the largest? Should I get my camera looked at by Canon? Thanks in advance.

I was advised (on this forum) only to use the center point for AF. I set my camera only to use this point and have done so ever since. I'll be interested to hear if you get very different suggestions.

I never use anything other than center point focusing. It works very well, so I don't use any of the other focus points.

Does this happen with all your lenses, or one in particular, or not a particular lens? The center point is most sensitive, and is the only one that will work on both horizontal and vertical edges. If you have the problem with your slower lenses, or the surfaces you're lining up on are the "wrong" orientation, the sensor will have more trouble. If your focussing screen is slightly out of alignment, the outer AF markers (which are not the place where the AF sensors are located, they're the mapping of those points onto the screen - actual focus points are at the bottom of the mirror box) will be more affected by this misalignment than the center one, so you might not be focussing on what you thought you were.

It could be that the aperture of your lens is limiting, the subject is too dark or not contrasty enough. The center AF point is more sensitive than the others, and focusing accuracy will depend upon the maximum aperture of your lens. Thats one of the performance features you purchase with a f1.2-2.8 lens.
However, it should be noted that Canon strongly suggests not using focus, lock and recompose. There was a big thread recently debating the utility of the FLR method.
http://www.fredmiranda​.com/forum/topic2/3250​57/0#2753529

To summarize that thread:
Many who use FLR do so mainly because of the required speed needed to capture the moment and the button pushing required to change the focus point. Working handheld it is very easy to use the FLR method, and in most scenes it works fine. The instances it will work poorly are: larger apertures (thus less dof), closer distances (especially macro), moving subjects, and where there are large bightness contrasts between the center point and subject. The last issue has to do with how you set up your Custom Functions to link or uncouple your focus point from your metering and if they are performed with differning button pushes. Getting exposure right is even more complex if you have ETTL II. If you are shooting with a tripod, it would be worthwhile to spend the time to move the focus point.

Taken from the thread mentioned above:
This text is taken from pages 18 of:
http://www.photoworksh​op.com/canon/EOS_Digit​al.pdf

"Background
Traditionally photographers have used th FLR (focus, lock, recompose) method when
interfacing with their camera and their subject. This is how it had to be done with
manual focus cameras and the early auto-focus models with a single focusing point.
Almost everyone knows how to use FLR, but it can cause problems. First, it’s not nearly as fast as some of the methods we’ll discuss here. Metering is less precise, particularly flash metering. Additionally, it can lead to backfocusing problems when shooting at wider apertures within 15 feet of the subject.

The fastest and most accurate way to work is to compose first and then use the benefits of the 45-point Area AF sensor to get your focusing and metering settings.

By using this Event combination, the photographer obtains many focusing options, all
without having to take attention away from the subject. It also allows the scene to be
composed in the viewfinder prior to choosing a focusing point. This is helpful because
in shooting these types of events, people are unpredictable in their movements and
with a quick flick of the thumb the photographer can be ready for any rapidly changing
shot without having to lock focus and recompose. Compose the shot, and then just pick
the point that works best.
Another advantage is that when using this combination of settings with Evaluative
Metering, the camera will give more precise metering for your intended subject and do a better job of automatically compensating for backlighting and unevenly lit scenes.
For EOS-1D and EOS-1Ds cameras that use E-TTL (not the newer E-TTL II), this
combination will also give you much more reliable flash exposures when you’ve chosen
a focusing point that lands on your subject, rather than using FLR.

It will take some practice to break the habit of FLR, but once you learn how to use the
45-point AF system effectively, it can really improve your performance as a
photographer."

Obviously the above was written for the 1D series cameras, but the principals apply accross the Canon dSLR line. I am not criticizing the use of FLR, just noting that it is not the recommended technique and has some potential pitfalls to be aware of.
Mike K

Most camera lenses produce a flat field of focus: if the camera is swung around in an arc to "re-compose", the original focussed subject will require a different focal length to be sharp. How obvious the out-of-focus will be depends on many factors. See EOS Magazine, June 2005, p30-31 - "Star Treatment".
www.eos-magazine.com

Thank you Mike for taking the time to explain what we should be doing. But how? I find selecting one of the 7 AF points on my 350D takes about 4-5 secs. It's not 'a quick flick of the thumb' with me. I have to find the button, then rotate the little wheel until the correct point is highlighted then re-focus. It just takes me too long. FLR is quicker for me I suppose because I've done it for so long. Any advice?

Canon engineers designed it that way to encourage you to upgrade to the 20D, where you can put it on the "joystick" ;{)#
Sorry - with the 350D you need to mash the AF selector button then use either the main dial or the Cross Keys (correspond to the Quick Dial on the 20D). From the sound, you're using the Main Dial. You might want to try the Cross Keys.

Mike K wrote:
It could be that the aperture of your lens is limiting, the subject is too dark or not contrasty enough. The center AF point is more sensitive than the others, and focusing accuracy will depend upon the maximum aperture of your lens. Thats one of the performance features you purchase with a f1.2-2.8 lens.
However, it should be noted that Canon strongly suggests not using focus, lock and recompose. There was a big thread recently debating the utility of the FLR method.
http://www.fredmiranda​.com/forum/topic2/3250​57/0#2753529

To summarize that thread:
Many who use FLR do so mainly because of the required speed needed to capture the moment and the button pushing required to change the focus point. Working handheld it is very easy to use the FLR method, and in most scenes it works fine. The instances it will work poorly are: larger apertures (thus less dof), closer distances (especially macro), moving subjects, and where there are large bightness contrasts between the center point and subject. The last issue has to do with how you set up your Custom Functions to link or uncouple your focus point from your metering and if they are performed with differning button pushes. Getting exposure right is even more complex if you have ETTL II. If you are shooting with a tripod, it would be worthwhile to spend the time to move the focus point.

Taken from the thread mentioned above:
This text is taken from pages 18 of:
http://www.photoworksh​op.com/canon/EOS_Digit​al.pdf

"Background
Traditionally photographers have used th FLR (focus, lock, recompose) method when
interfacing with their camera and their subject. This is how it had to be done with
manual focus cameras and the early auto-focus models with a single focusing point.
Almost everyone knows how to use FLR, but it can cause problems. First, it’s not nearly as fast as some of the methods we’ll discuss here. Metering is less precise, particularly flash metering. Additionally, it can lead to backfocusing problems when shooting at wider apertures within 15 feet of the subject.

The fastest and most accurate way to work is to compose first and then use the benefits of the 45-point Area AF sensor to get your focusing and metering settings.

By using this Event combination, the photographer obtains many focusing options, all
without having to take attention away from the subject. It also allows the scene to be
composed in the viewfinder prior to choosing a focusing point. This is helpful because
in shooting these types of events, people are unpredictable in their movements and
with a quick flick of the thumb the photographer can be ready for any rapidly changing
shot without having to lock focus and recompose. Compose the shot, and then just pick
the point that works best.
Another advantage is that when using this combination of settings with Evaluative
Metering, the camera will give more precise metering for your intended subject and do a better job of automatically compensating for backlighting and unevenly lit scenes.
For EOS-1D and EOS-1Ds cameras that use E-TTL (not the newer E-TTL II), this
combination will also give you much more reliable flash exposures when you’ve chosen
a focusing point that lands on your subject, rather than using FLR.

It will take some practice to break the habit of FLR, but once you learn how to use the
45-point AF system effectively, it can really improve your performance as a
photographer."

Obviously the above was written for the 1D series cameras, but the principals apply accross the Canon dSLR line. I am not criticizing the use of FLR, just noting that it is not the recommended technique and has some potential pitfalls to be aware of.
Mike K

Thanks for the info, I totally agree with this, but in practice I get poor results using this method. I actually get much better results with FLR, which is the opposite of what I would expect. Do you think my camera is faulty?

Oh and I am using the Tamron 2.8, so its a fairly large max aperture, so that shouldnt be a problem either. This lens focuses perfectly when using the centre point too.

Jon - do you have a link that explains what you wrote further, I think you may have the answer to my problems, I am just having trouble grasping the concepts.

Ok I did some searching and I came up with this info in another thread. http://www.fredmiranda​.com/forum/topic/24152​4
I think my camera is normal after all, I just need to find a line that runs perpedicular to the focus point to achieve accurate focus. Thanks to those that replied! Hopefully I can get this focusing working perfectly now.