Canon: Selecting AF point?

c18913

I'm a bit confused about this ... can someone walk me through your thought process about when to change the AF point from the whole array of nine to a manually selected point?

Is there any value in using just the center point? Is it best to keep it on all nine? I've read the manual and the Peter iNove e-book, but I'm still not getting the "point" (no pun intended!!)

I'm not clear on why you would do this if you can pre-focus, then recompose when dealing with an off-center subject.

Thanks so much for all your help.

Mike Lane

Why Focus Recompose Sucks.

Anyhow, FWIW (I'm assuming you're talking 20D here) I always have all 9 selected unless I am trying to focus on one thing in a distracting environment or if I have something in very near foreground that should be OOF I'll set the AF point to match up with the subject.

I wouldn't call that much of a technique, just a make-it-work-ism ... uh ...

wxwax

Here's an example of using an off-center focus point. Narrow depth of field, so center focus and recompose was dangerous. Too much in the shot to be sure that the camera would grab the correct focus point using all nine. AI Servo might have worked, but might have grabbed the wrong part of the train. Manual focus might have worked, but focus is difficult to guage on these small viewfinders.

Because I knew where in my frame I wanted to focus, I could preselect a point, and when the train came through that point I could accurately grab focus and shoot.

wxwax

Mike Lane wrote:

Why Focus Recompose Sucks.

There's no question there are dangers to 'focus-recompose.' I think some folks use those reasons to dismiss the technique entirely. This is a mistake, as 'focus-recompose' works, as long as you're aware of when not to use it.

ginger_55

I keep it on one pt, center, unless I can think of a reason not to.

I have taken it off of center pt, to all nine and been very sorry.

Sid, I see your "point" perfectly on the model train. If I ever have such a setup I hope I remember to use the correct point.

When I was just learning these cameras, I was always on all nine points. When I had been doing birds for awhile, I found center point. I am kind of used to it by now. Don't know how I did it before, as well as I did, with all nine pts, but that is just me.

Actually, why do you who do, why do you want all nine points?

ginger (Maybe I can learn something. I know why/when I want one point. Why/when do I want all points????)

System

thank you for a very good example, Sid-

I usually stay on the center, focus and recompose, but I need to be educated more on this subject-

ginger's question is mine: when and why all nine? a group portrait? should you be on P or Tv to allow the aperture to change for dof if need be?-

thanks
george

System

Mike-

thanks for the link-

when I do the center point and then recompose I'm doing the shutter half-way down lock the af thingy, to put it in technical terms-

george

firedancing4life

good question...I too wonder the same thing...but I find myself using the center the most...or one off center if I know I want to off center the subject. Sometimes I'll use all 9 and press half way until I find the desired focus area.

Jeffro

Points....
The 20D makes it real easy to choose the correct focus point. Hit the focus select button with your thumb, spin the dial! Takes some practice, but is worth the effort!

If you're not using them, why pay for them?

ivar

Jeffro wrote:

If you're not using them, why pay for them?

Canon is supposedly out of 20d's with one focus point...:D

Jeffro

There must have been a big demand from all the one pointers above!

Bodwick

A screen shot from Canon File Viewer showing focus points.

I've selected to move the point to the front wheel rather than the clutch bar end.
Moves the focus line to the centre of the bike.
I'm sounding a bit anal here...


Bod...

TristanP

Jeffro wrote:

The 20D makes it real easy to choose the correct focus point. Hit the focus select button with your thumb, spin the dial! Takes some practice, but is worth the effort!

If you're not using them, why pay for them?

Even easier on the 20D is to set Custom Function 13 to "1", allowing you to use only the joystick to pick your focus point, rather than hitting that button on the back first. Makes it much easier.