focus point problems

[carrbowl]

I have had issues in the past with focusing problems. I tried just using the center focus and it seemed to make a huge difference. Could this be possible. Is it me or the camera or is there a way to tell?

[kenw]

the huge difference was better? which were you using before?

[carrbowl]

I was using the outside focus points for the most part...

[JohnT]

When using an outside FP, you would put the point on the subject, focus, then shoot without recomposing, right?

[carrbowl]

correct John...and that is what I did yesterday with the center point too. In the past I thought I was doing something wrong. Now I am starting to believe it might be the camera...since I did the exact same thing, but with the center point. I am wondering if that is possible..and how you check it??

[JohnT]

To make a good, reliable test, you would need to put the camera on a tripod and photograph a focus test chart (find one online that you can download). Then examine the results at 100%.

[linque]

You can download a focus test chart and instructions here.

[CaptainTom]

move your focus select to the * button on the back of the camera.
Once you master this technique, your focus issues will go away.

[johnastovall]

Canon's problems with the outer focus points is a well known problem.

[Collins]

Originally Posted by CaptainTom

move your focus select to the * button on the back of the camera.
Once you master this technique, your focus issues will go away.

Dunno about that.

What model camera are you using? The outer focus points are less accurate in general on most cameras and on older cameras (for example, the 20D), are only sensitive to contrast in one direction making it harder to get an AF lock in many circumstances.

[carrbowl]

Originally Posted by johnastovall

Canon's problems with the outer focus points is a well known problem.

This is what Canon told me. Not that it is a problem, but less reliable. Because the center focus mmmm...I can't remember exactly what he said, but something similar to the center focus point will examine the point horizontally, vertically and diagonally, where as the outside focus points do not do that.

So that might not be the exact explanation but you technically folks can explain it so the other technical folks can understand!!

So I'm still playing..I just have to say, that 5D got me some sharp photos like I haven't seen since I first got it. And I have been using the center and outer focus points, pressing the shutter half down, all the tricks everyone has showed me, and nothing has seemed to matter. So something changed the other day...?? We'll see if I can duplicate it on another shoot.

So tomorrow I'm hopefully going to try the test and will post the results, maybe you guys can help me decide if there is some sort of issue...with the camera that is!!!

[Shane]

Just remember, if you focus and then recompose . . . your focus could be off as the distance between you and your subject changes slightly when you recompose, so depending on how wide open your f/stop is, you might lose that sharpness.

[johnastovall]

Originally Posted by carrbowl

This is what Canon told me. Not that it is a problem, but less reliable. Because the center focus mmmm...I can't remember exactly what he said, but something similar to the center focus point will examine the point horizontally, vertically and diagonally, where as the outside focus points do not do that.

So that might not be the exact explanation but you technically folks can explain it so the other technical folks can understand!!

So I'm still playing..I just have to say, that 5D got me some sharp photos like I haven't seen since I first got it. And I have been using the center and outer focus points, pressing the shutter half down, all the tricks everyone has showed me, and nothing has seemed to matter. So something changed the other day...?? We'll see if I can duplicate it on another shoot.

So tomorrow I'm hopefully going to try the test and will post the results, maybe you guys can help me decide if there is some sort of issue...with the camera that is!!!

If it's less reliable it's a problem.

[AndrewCCM]

Outer AF points are definitely not as sensitive or accurate as the center one, and on many bodies, are not cross type sensors. The center point on nearly all Canon bodies will perform much better than the peripheral ones.

What lenses? Maximum Aperture plays a role too since the peripheral points are not as sensitive. Faster glass will AF better regardless of F-stop due to the AF mechanism using the widest/largest aperture available. It stomps down to the "chosen" aperture once the shutter is released.

[CaptainTom]

In my opinion the "half press" focus on DSLR's is a throwback to point and shoot cameras. No brain needed. Might as well put everything on P and just let the camera decide what to do. Maybe face recognition in DSLR's is next?