Depth of field is usually described as
the amount of the frame that is in sharp focus. When we look at a scene
with our naked eye almost everything appears sharp. But that is not the
case when we compose the same scene with cameras. Some part of it is
blurred out. The more the frame is in sharp focus, the more is the depth
of field and vice versa.
Depth of field (DOF) depends on two factors: aperture and distance of the subject from camera (magnification). Wider aperture and closer subject give the shallower DOF.
There is an inverse relationship between
the aperture of your lens and the depth of field. Narrower is the
aperture more is the depth of field. Usually when you set your lens to
f/1.2 or f/1.4 (in a prime lens) or f/2.8 (in a zoom lens) a soft blur
is created around the back and front of the subject. This is also known
as bokeh.
When this happens only a small part of the frame (depending on where
you’re focusing) is n sharp focus and the rest is blurred out.
When you reduce the aperture the whole
frame starts to get into sharp focus. The narrower the aperture the
sharper is the image. As you move from of f/4 or f/5.6 all the way to
f/11 and beyond the images get sharper and sharper. The reason is the
light rays reflected against the subject and passing through the
aperture gets refracted by the front element of the lens and meets the
sensor at a precise point creating a sharp image. Narrower the aperture
more precise is this meeting of light creating a sharper image and thus
bigger depth of field.
Depth of field also depends upon the
kind of lens that you use. A wide angle prime lens offers more soft blur
because it has a wider aperture. But if you stop down to f/8 and even
narrower, a large depth of field can be created. A wide angle lens
reduces the perspective of the subject as it fits in more inside the
frame; also know as field of view. As such a hut on the beach will
appear smaller than the actual real life size when the picture is
finally taken. On the other tele lenses have an effect of increasing the
size of the subject on the final image. The higher magnification allows
you to capture more detail of the subject but also reduce the field of
view and the depth of field.
Basic tips to play around with depth of field
Set your aperture to a minimum of f/8 to
make sure you have a good platform to start with. Always ensure that
you zoom out and exploit the widest limits of your lens, even if you’re
using a tele lens. Tele lenses have a narrow maximum aperture so once
you have zoomed out completely you may still have an aperture of f/4 to
start off. Wide angle lenses can pack in a lot provided you can start at
f/8 or even narrower. When shooting landscape or any other subject,
never focus on the infinity. Always focus on something closer so that
you have a sharp depth of field behind the point where you’re focusing.
No comments:
Post a Comment