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What is Depth of Field?

Depth of field in photography is a reference as to how much of the area in an image appears to be in sharp focus.
In some photos, the entire scene might appear to be in focus. In other photos, the main focusing point and a certain
amount of the area around it will appear to be in sharp focus while the background and foreground will be out of focus.

Images in which the subject and most of the
background and/or foreground are pretty much
in focus are said to have deep or wide depth of
field. Images in which the subject is in focus but
the background and/or foreground are out of
focus are said to have shallow depth of field.

Wide or deep depth of field is useful when you
want just about everything in your photo to be in
sharp focus. Shallow depth of field is good for
making the main subject stand out more against
the background.

Notice how the large flower in image #1 as well as
everything behind it seems to be in focus. That is
an example of wide or deep depth of field. Next,
take a look at the flower in image #2. The flower is
in focus, but everything in the area not too far
behind it is out of focus. That is an example of
shallow depth of field.

There are three main factors that determine the depth of field in photography. They are the size of the camera lens
aperture opening (F Stop), the camera to subject distance, and  the camera lens focal length.

Camera Lens Aperture Size: The lens aperture opening size plays a big part in the depth of field in  an image.
Pictures taken using wide aperture openings like F2.8 or F3.5 will tend to have a more shallow depth of field. Pictures
taken using small aperture openings  like F11 or F16 will have a deep or wide depth of field.

Just keep in mind that the lens aperture setting alone will not completely determine the depth of field in an image. As we
previously mentioned, the  lens focal length and camera to subject distance also play a part in determining the depth of
field in a photo.

If you are not familiar with the function of the camera  lens aperture, check the
Lens Aperture tutorial for a few more
details about it.

Camera to Subject Distance: The closer you are to your focal point or subject, the more shallow the depth of field will
be. That is as long as your lens aperture size and lens focal length remain the same for that subject. Of course, the
opposite will be true if you move further away from your subject.

Camera Lens Focal Length:  The focal length of a lens is also a factor in determining the depth of field in an image.
Using a longer focal length like 300mm will generally produce more shallow depth of field than using a shorter focal
length like 50mm.

In review, the camera lens aperture, the camera to subject distance, and the camera lens focal length all help
determine the depth of field in photography. However, the type of equipment you are using will also make a difference if
you are trying to control the depth of field in an image.

For instance you cannot manually control the lens aperture with most basic
Compact Cameras. The best you can do
with those type cameras is use one of the pre-set modes like portrait or landscape.

When using those modes, the camera will set larger aperture openings for the portrait mode and use smaller aperture
settings for the landscape mode. (The assumption is that you might want more shallow depth of field for a portrait and
deep depth of field for a landscape shot.)

If you are using a
Digital Slr camera like the Nikon D3200 or Canon T4i, you can manually control the lens aperture
settings. That will give you more flexibility in controlling the depth of field. However, even then, the
type of lens and the
lens aperture settings available at a given focal length for that lens are factors in controlling depth of field in an image.

There are more technical aspects to depth of field, but hopefully this has given you a basic understanding of Depth of
Field in photography.
Image #1-Deep Depth of Field
Image #2 -Shallow Depth of Field
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