Focus

Pardon what I imagine will turn out to be a fairly dumb question:

In a number of posts I read about focusing on something and then composing the shot. Can someone explain the process or point me to a thread that does.

Currently I am placing my focal point over what I want in focus, pressing half way, confirming auto focus and taking the photo. I get the idea I am missing something?

As long as you don't change the distance from your subject you should be fine.

Northwoods Bill wrote in post #14890988
Pardon what I imagine will turn out to be a fairly dumb question:

In a number of posts I read about focusing on something and then composing the shot. Can someone explain the process or point me to a thread that does.

Currently I am placing my focal point over what I want in focus, pressing half way, confirming auto focus and taking the photo. I get the idea I am missing something?

What you're talking about is the "focus and recompose" technique where instead of having the subject positioned always on one of the AF points, you focus, then reframe the shot so that the subject is where you want it to be to make the best composition. Also, this is frequently used when the centre point is more sensitive than the outer points (as is the case on most, if not all cameras) so as to have a better chance of accurate AF. For example, if you're taking a portrait of someone with a fast lens, you may wish to use the centre point as it is more accurate when used with lenses of f2.8 or faster, but you may not want the subject's face to be right in the middle of the frame, so you'd focus on the eyes, then move the camera slightly to position them off centre or whatever.

This however, has the downside of possibly moving the plane of focus sufficiently far to throw the subject out of focus if your DOF is very narrow, and/or your movement too large; when you tilt or turn your camera, as you will when recomposing, the plane of focus moves correspondingly.

TheRisingArms wrote in post #14891031
As long as you don't change the distance from your subject you should be fine.

For the last reason in the reply to the first quote, this is not always correct.

Sirrith wrote in post #14891080
For the last reason in the reply to the first quote, this is not always correct.

Technically it is though, is it not?

TheRisingArms wrote in post #14891096
Technically it is though, is it not?

If you focus and recompose by shifting yourself sideways, up or down without tilting the camera at all, then yes, but how often do you do that? I know I never

I used to use the focus and recompose method quite a lot but due to the problems described above with the technique, I find it better to frame the image the way I want it, and then simply shift the focus point being used (I almost always shoot with a single point only) to where I want it.

onona wrote in post #14891138
I used to use the focus and recompose method quite a lot but due to the problems described above with the technique, I find it better to frame the image the way I want it, and then simply shift the focus point being used (I almost always shoot with a single point only) to where I want it.

for those of us without 12793127398 focus points, its a bit problematic

IF the center focus point is on the eyes, then you're good when shooting wide open.
Otherwise, look in your "Custom Functions" & put the choice of focus point under your control.
And I use AI Servo with that, so that if you or the subject moves a little bit, the eyes will still be sharp.

Good explanation of why center focus, while more sensitive, doesn't always result in a sharp shot.
http://www.visual-vacations.com …focus-recompose_sucks.htm

PhotosGuy,
Thanks. Just read it from end to end. Had not developed the habit and looks like I am not going to!

Wow, Frank. I agree with Bill. No more focus-recompose for me, at least for close subjects.

If you recompose while keeping the focal node (whats the name again?) in the same spot, and the lens has a spherical focal plane, then there are no problems with focus and recompose. While neither will usually be the case, you will have problems, but 90% of the time i'd say they would be minimal unless your settings result in a very shallow DOF as has been said. Actually the more i think about it, do any lenses have spherical focal planes? Fishe eyes?