Hand in 2nd February 2020
Judged 11th February 2020
Judge Stephen Womack
What is Depth of Field (DoF)?
DoF is the zone of acceptable sharpness within a photo that will appear in focus. In every picture there is a certain area of your image in front of, and behind the subject that will appear in focus. For this competition we are looking for photos in which at least part of the picture (either foreground, background or both) is deliberately out of focus. How shallow the area of sharpness is in distance will depend on the subject and genre of the photo – for example, macro photography will always produce a shallower depth of field than the deliberate use of out of focus sections of a landscape for creative effect (landscapes are more conventionally intended to be sharp throughout).
What Affects Depth of field (DoF)?
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. You can if you wish download a free depth of field calculator to your phone.
Aperture refers to the access given to light from the lens to the camera sensors. The size of your aperture (the diameter of the hole through which light enters the camera) controls the amount of light entering your lens. Using the aperture (f-stop) of your lens is the simplest way to control your depth of field as you set up your shot. A general rule of thumb is:
Large aperture = Small f-number = Shallow (small) depth of field
Small aperture = Larger f-number = Deeper (larger) depth of field
The closer your subject is to the camera, the shallower your depth of field becomes. Therefore, moving further away from your subject will deepen your depth of field.
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. For example: if 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 (23.4 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.
What is a shallow depth of field (DoF) and what is it used for?
A shallow or small DOF might be used when only a small amount of the image is in sharp focus while blurring any background or surrounding areas in view that could distract the viewer’s attention.
Using a shallow depth of field is a good way to make your subject stand out from its background and is great for portrait photography. Shallow DoF can also be useful in wildlife photography where you want the subject to stand out from its surroundings. This is also useful because many wildlife photo opportunities are low light situations and increasing your aperture size will give you more light. Shallow DoF is also effective for sports photography where you might want to separate the athlete from the background to bring attention to them. The result of this can also help give you a fast enough shutter speed to freeze the action.
What subjects can I use?
The use of a small depth of field can be used in many situations where you want to isolate your subject from the background or the foreground. It does lend itself well to sports, wildlife and portraiture but can be used for effect in many other genres. When using a large aperture, you will need to understand the exposure triangle (aperture, shutter speed and iso) to balance the exposure. Remember that when using a small DoF the composition of the photograph is still very important and so some prior planning and preparation will make your photographs much better.