Understanding and Using Depth of Field for Better Photos
Get expert advice on DoF for beginners:
Depth of field is an important concept to understand in order to get the best photos possible.
In a nutshell, DoF is the area in your photo that is in focus. This is not a default setting and it is not the same as focusing the lens.
You can have a shallow depth of field, meaning the background (or foreground, or both) are blurry. Or you can have a deep depth of field, where pretty much the entire image is super sharp.
Three main factors that will affect how you control the depth of field of your images are: aperture (f-stop), distance from the subject to the camera, and focal length of the lens on your camera. Here are some explanations and answers to other common questions concerning depth of field.
The aperture controls how much light enters the camera. It may seem like you want to open the aperture up then to get all the light in. It isn’t that simple. The larger the aperture, the blurrier the image.
This is why controlling depth of field is achieved by a combination of tools.
Large aperture = Small f-number = Shallow (small) depth of field
Small aperture = Larger f-number = Deeper (larger) depth of field
The second part of the equation is to move away from your subject. If you are very close to the subject you will not be able to have deep DoF.
Your lens will also affect your DoF, specifically the focal length of the lens.
Focal Length refers to the capability of a lens to magnify the image of a distant subject. This can get complicated, but the simple answer is that the longer you set your focal length the shallower the depth of field. Example: Your subject is 10 meters (33 feet) away, using a focal length of 50mm at f/4; your depth of field range would be from 7.5 -14.7 meters (24.6-48 feet) for a total DOF of 7.2 meters (23.6 feet). If you zoom into 100mm from the same spot, the depth of field changes to 9.2-10.9m (30.1-35.8′) for a total of 1.7m (5.7′) of depth of field. But if you move to 20m (66′) away from your subject using the 100mm lens, your depth of field is almost the same as it would be at 10 meters using a 50mm lens.
One of the reasons to use a shallow depth of field is to let the subject pop from the background. In some cases the image would be so busy that we will lose the subject. Our human eye will not be able to figure out when looking at the photograph what it was that captured your interest in the first place.
Play with taking shots of the same subject with both shallow and deep depth of focus.
Read the entire lesson by Bruce Wunderlich at Digital Photography School
Photos by Bruce Wunderlich