the presenter suggested several ways in which to improve one's pictures:
1- use only the center focusing spot- it is more accurate than multispot
2- Constant aperture, faster glass will focus faster because more light gets to the focusing sensor
3-dof is greater will smaller sensor size digital cameras, so the wider apertures of faster glass will enable the photog. to control dof better.
The third is true from my observations, but has any one tested or know of a trest to confirm the first 2 statements; both make sense to me.