20D Focus points

[tommykjensen]

Exactly how is the focus points supposed to work?

If I select all points to be used the camera is supposed to select the best point(s) correct?

I can also select each individual.

In basic zone the camera use all automatically and when half-pressing the shutterbutton one or more lights red. This also occurs in green box and A-Dep. But not in P, Av, Tv and M ? Does the camera always use only the middle in these modes?


For my last shoot (http://photography-on-the.net/forum/showthread.php?t=43796&highlight=) I had selected all focus points and used P mode as well as AI Servo. But on all the photos I have checked so far the middle point was used to focus. Resulting in a lot of out of focus shots :(

[CyberDyneSystems]

Essentially.. letting the camera decide what point to use is a recipe for disaster.

The ONLY time it makes sense to use ALL focus points is when you are trying to track a moving subject in AI servo focus mode.. in which case the Camera can use all 9 points and MAY do a better job of keepng the subject focused than you can.

At all other times.. it is HIGHLY recomended that you decide and select the correct focus point to use manually.

Fortunately with the 20D this is easier than with any other camera.

Set Cunstom Function 13 to setting "1"

Now .. when you press the multi eraser in the center, you get center focus,. or you can use the multi eraser thing to select any of the nine AF points by pushing the "eraser head" in the appropriate direction.

When you DO want all nine AF points to be used by the camera to track a moving subject.. then press the right most rear button "+" with your thumb. All Nine af points will then be selected.

[tommykjensen]

I normally use centerpoint but for this flying action I wanted to use all points hoping that I would get better results than with my 300D - based on todays result 300D won in that category sofar !

Next time I will try sportsmode :shock:

As for the joystick, I haven't gotten used to that yet. Also it is a little to far to the left for my thumb to reach it.

[CyberDyneSystems]

Tommy,

In light of the additional info in this thread;
http://photography-on-the.net/forum/posting.php?mode=reply&t=45565

I think I know the problem.

The center AF point was used in all the shots because you were shooting with a T-con.

When this occurs is not completely consistent from lens to lens.. but I do know that using a T-con EVEN when AF is retained often the T-con will force you to work with the center AF pint only. This is even true of the 1D series cameras.. (albeit at smaller apertures)

Since you were in AI Servo AND had all 9 points selected on your end,.. the cameras default to the center point did not light up for you. (actually I don't know if it would have lit up in single shot either but I think it would)

At some point you may want to try all 9 AF p0ints and AI servo again when you don't have a T-con on.

[tommykjensen]

I also thought that it might be the extender. So I will try without it next time.

Hopefully the sun will shine a little next weekend.

[davidwegs]

All Canon bodies (recent years) default to the center point when you introduce 1.4x or 2x between the body and lens. There are, as best I remember, no ways around this :(

[tommykjensen]

All Canon bodies (recent years) default to the center point when you introduce 1.4x or 2x between the body and lens. There are, as best I remember, no ways around this :(

That could be an explanation but following was shot in portrait mode with the 70-200 mm f4 L and the 1,4x extender. See the focus point that is lit.

http://photo.klein-jensen.dk/photohtml.php?n=focuspoint.jpg