Over the last few weeks, we have concentrated on making images, compositions, Automatic and some features in Program Mode (exposure compensation and white balance).
Continuing along the theme of making images, this week, we look at Depth of Field, what it is and how to achieve it when making images.
This post will be split over two weeks as it’s a hefty area of image making, next week will be the more technical aspect of controlling depth of field.
What is Depth of Field (DOF)?
In the most basic terms, depth of field is how much is in focus from the end of the camera lens to what you see in the distance. It can be a little or a lot. Focus is the point you intend to be sharpest within depth of field.
Imagine an elastic band with the capacity to stretch a mile.
When the band is not stretched, the depth of field is small, i.e., 4 inches. Anything within the length of the band is acceptably sharp (including the focus point). Anything outside of the length of the band is blurred.
When the band is fully stretched to a mile, this is broad depth of field. Everything from the end of the lens to one mile away will be acceptably sharp (including the focus point) .
Depth of field is always from your viewpoint and stretches in the direction you are looking.
Let’s look at this from a different angle (i.e., from the side). In the image below and using the relaxed elastic band metaphor. From the photographers viewpoint, you can see the band of focus is small and only one person fits within it. They are in focus whilst the people beyond the focus band are out of focus (blurred). This is a shallow depth of field.
In the next example, the band has been stretched out and now everyone fits within the focus band. This is a broad depth of field.
Why is depth of field so important?
It comes down to the detail you intend to include when you photograph. As a landscape photographer, broad depth of field is used for landscape scenes. Landscapes are more distant subjects. In the example below, note the grass at the bottom of the frame is detailed, as are the trees on the distant hills.
However, as a creative photographer capturing flowers, you might want to use shallow depth of field to isolate one flower from a bunch and make it the subject, as seen below. A broad depth of field makes all the flowers detailed and multiple subjects fight for attention.
Shallow depth of field may be used to lessen distraction in the background and to direct the viewers eye to the intended subject. With the flowers above, a shallow depth of field was used to separate the foreground flower from the mass of flowers in the background.
Typically as onlookers, viewers deem primary subjects to be the biggest subject, the sharpest subject and/or the brightest subject (or combination of these three factors). The secondary subject in this instance would be the next biggest/sharpest and/or brightest item in the scene.
How do I control Depth of Field?
There are three things affecting depth of field. Distance, focal length and aperture.
Distance has a major impact on depth of field, the further away the subject is, the broader the depth of field is going to be regardless of aperture used. Photographing flowers more than a meter away with a standard kit lens (18-55mm) reduces the shallow depth of field effect. Whilst photographing subjects closer to the lens increases shallow depth of field by blurring out the background quicker.
Focal length, i.e., how zoomed in the photographer is to the scene. Greatly zooming in at larger apertures can make depth of field shallower. Telephoto lenses are referred to as ‘soft’ lenses (shallower depth of field), whilst wide lenses are ‘hard’ lenses (broader depth of field).
Apertures are the F-number settings in camera. F3.5 achieves a shallow depth of field whilst following proper procedure. Larger F-numbers broaden the depth of field. More will be revealed about Apertures in next weeks post, join us then.
Summary
Focus is the sharpest point in a scene (this should be the subject). Depth of field is how much clarity is within the band of focus from your viewpoint (which includes the focus point).
Depth of field varies but is used to show off the intended detail of the subject from the foreground to background of the scene.
Depth of field is affected by distance, focal length and aperture: all of which depend on the size of the subject and how much detail is intended to be captured.
Join us next Monday to learn more about apertures and how to control depth of field.
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