Keeping your shot in focus is something you'll spend most of your time as a
camera operator doing. Some cameras and lenses are easier to focus than others
and as we saw in the episode on Aperture, the F-Stop your lens is at can make a
big difference as well.
Autofocus systems are becoming more and more advanced all the time, which can
be a great help in some situations. But whether your using autofocus,
focusing manually yourself, or even if you have a focus puller on set with you,
you’ll need to have a basic understanding of what focus is, and what it can achieve.
So lets look at a diagram. Heres the camera, and this box represents
whats in focus,
referred to as your depth of field. As you turn the focus wheel on your lens,
the area thats in focus is going to get further away, or closer to the camera
depending on which way you turn. The further away from this box something
in your shot is, the more out of focus it will be. Also its worth noticing that
the closer to the camera you focus, the smaller your depth of field becomes.
We use several terms to describe how big this box is, and how much of
your shot is in focus,
deep and shallow. A shot with deep focus will have a wider depth of field,
and lot more of the shot in focus. This has several advantages, firstly its easier to
get the shot in focus in the first place, and also your subject will have space to
move around a bit without going in and out of focus. Notice though that the background
in this shot isn't very out of focus at all.
The opposite is a shot with shallow focus, this means that a very small amount of your
shot will be in focus. This is often something thats very desirable,
because it is an easy way of making your shot more visually pleasing, and more
importantly, it isolates your subject. This means that the audience will be
looking at exactly the part of the image you want them to be. It does mean though, that it
will be harder to not only get in focus to start with, but to keep focus as the action happens
and your subject moves. Several factors dictate how deep or shallow the
focus in your shot will be, the first is the aperture you set on your lens.
A low aperture, F1.8 or 2.8 for example, will give you really shallow
focus. Whereas if you use a higher aperture,
like F11 or 16, it will mean you'll have much more of your shot in focus.
Your focal length will also have a big impact, F1.4 at 24mm will have
a deeper depth of field than f1.4 at 100mm, so the
wider your shot, the deeper your focus will be, no matter which aperture your lens is at.
Sensor size also plays a big part. You will often hear people say that they prefer a full frame sensor so
they can get lovely shallow depth of field, thats because the larger
your sensor the shallower your focus will be. Thats does of course mean that it will
be harder to keep your images in focus, so there is always a trade off.
Its also worth mentioning that you can still get shallow depth of field with a
smaller sensor, you might just have to open your aperture wider, or
zoom in more than you would have to with a larger sensor.
So now we know how to change your focus, and what effects how
much depth of field you have, but what should you focus on? As a camera operator, you want
to keep your focus on your subject. Use it to tell the audience where to look,
if its a wide shot and you want the audience to examine the location and setting,
then make sure everything in that shot is in focus. But if you want them to
be looking at one person in particular, you’ll want to lower that aperture and keep
the focus on them, while letting everything else fall out of focus behind them.
One last quick handy tip is that if your doing a close up or an interview, maybe a shot like this one right now,
and your wondering where-abouts to focus on,
always go for the subjects eyes. If the eyes of the person your listening to aren't
in focus, then something is going to feel very odd for the audience.
If you have any questions at all about focus or anything else we cover here on
the channel, just leave a comment below and i’ll get back to you.
Thanks for watching