Research 18: Depth Of Field

What I did not really pick up on through my AS course was the absolute importance of depth of field when filming. Not only is it used for music videos, but is used an awful lot in films, and for the same reasons:
Having a very focussed/thin depth of field is a way of pointing out to the audience where they should be focussing their attention on screen. It is mainly used to portray emotion, but can be used for purely special effects, or even going as far as creating subliminal referencing, which engages the audience even further into the film.
Just the other night I went to the cinema to watch one of the latest romantic comedies that have come out, and could not stop noticing the use of depth of field on nearly every single shot that was taken. It was amazing to think about how much effort must have gone into taking each shot, but the end result was well worth it, with the filming coming off with a very professional look to it.
I have found a video on youtube which has helped me understand the reasons for understanding, and when to use depth of field;

This makes it that much more important to get the depth of field right for every single shot, so that the audience can gain a greater sense of what they are supposed to look at (i.e. there is more of an attraction to looking into a sharp area of an image, than to a blurred out are of image.. it is just an automatic thing, as humans, that we do)
If needed, I can edit in depth of field after shooting everything in-focus, with the help of Adobe After Effects of course. But I would much prefer to get the depth of field right whilst filming, it just comes off with that much more natural a feel.