My camera Canon 40D.
Now that it is clear as to how to lock the AF prior to recompose a scene [after earlier discussion in here in the forum]
I was reading the tutorial in here on the subject of "understanding Camera Autofocus"
I felt it would be better to keep active the "Central AF Sensor" alone to take photo of my family member in a scene off centred that would require recomposing my scene.
However further reading on the tutorial suggests:
Quote" If one were to instead use the central AF point to achieve a focus lock (prior to recomposing for an off-center subject), the focus distance will always be behind the actual subject distance—and this error increases for closer subjects. Accurate focus is especially important for portraits because these typically have a shallow depth of field."
So does that mean I would be better using one of the adjacent vertical line AF sensors to focus lock on my family member who will become off centred in my scene composition.?
The photo here shown was taken prior my understanding of Focus lock [This was taken without focus lock]