Depth of Field Explained
Understanding depth of field is key to beginning to take competent photographs. Depth of field is one of the most important adjustments you can make on any camera that can radically change the outcome you get when you press the shutter button. So what is depth of field?
It can be defined as the distance around your focal object in the picture frame–or the field of best focus. Artistically, it situates the viewer and can communicate so much about the relationship between the subject and the rest of the image. So how do you become a master of changing your depth of field?
Adjusting the lens aperture: how to change the depth of field
Okay now we won’t pretend that this rule for changing the lens aperture
(and thus altering the depth of field) is easy to remember. In fact, it even seems counterintuitive. Here we go: the smaller the aperture (F8 over F2, for example) the greater the depth of field in your final image.
As your subject moves further away from you, this also will lead to an increase in depth of field. Following on, in close ups, the depth of field is quite limited. Playing with this effect can produce interesting landscape images, such as the one above taken in the forests of Tasmania.
How aperture and exposure are connected
The relationships don’t stop there. Aperture and exposure are connected via light and focus. A smaller aperture of course lets in less light, which means a sharper and more focused image will be the result. Think of all those overexposed images you’ve taken before–aren’t they all blurry and impossible to make out?
Why you can change exposure with focal length
By manually changing the focus on the camera, you can also affect the depth of field. A longer focal length makes the differences in the focus more dramatic, which can reduce the depth of field in the final image.
This can be great to take some photos in urban areas where you have limited space to work in. It’s also great for portrait photography when you need to situate your subject in a dramatic way (sometimes it’s easier to learn through looking at someone else’s work than seeing depth of field explained). To the eye, objects will appear at the same size.
Revisiting the subject of close-ups, changing the focus distance can lead to increased magnification of your image. As an image becomes larger in the viewfinder, small variations in the depths of the subject mean the lens must be focused at varying distances from your sensor or your film.
This means that subjects closer to you require more careful setup to photograph. Mastering this setup means that you can take extremely detailed and impressive close-ups, such as the one above.
Once you’ve mastered the concept of depth of field, and how it works with the other controls of the camera, it will add a new layer to your photography. Instead of taking flat images, you can manipulate depth of field to truly take storytelling images with the camera and capture environments in all of their nuanced glory. A good way to start would be to look at work by some of your favourite photographers and see how they use depth of field to their advantage in creating dramatic images.