Mastering and understanding depth of field, and how to control it, will mean your portraits no longer have busy backgrounds and your landscapes will be pin-sharp from front to back.
There are three main factors that can effect depth of field and they are: the focal length you're using, the aperture you have selected and the distance between the camera and your subject.
The most common and probably easiest way to control depth of field is by turning your camera's mode dial to aperture priority. In this mode, you change the aperture while the camera selects a shutter speed to create the correct exposure for that particular scene. The smaller the f number (wider aperture) the shallower your depth of field will be. So a small f number will allow your subject to stand out from its background while a higher f number (f/16 for example) will help keep more of the image (front to back) sharp and in focus.
To further ensure the scene has total front to back sharpness you can use something called the hyperfocal distance when setting your shot up. This is the distance that you should focus on to maximise depth-of-field, thus keeping the whole scene sharp. When the lens is focused at this distance, all objects at distances from half of the hyperfocal distance out to infinity will be acceptably sharp.
For tips on using hyperfocal distance, take a look at our article
which includes Depth-Of-Field Hyperfocal Distance Charts.
Generally, the longer your focal length, the shallower your depth of field is so when shooting with a zoom lens, such as a standard 18-55mm, the longer end of the zoom will be great for portraits while the wider, shorter 18mm end will allow foreground and background detail in landscapes to be sharp.
Camera And Subject Position
The closer you stand to your subject the more limited the depth of field becomes. This becomes even more apparent when shooting close-up subjects as it can extend to just a few millimetres in front and behind your subject.
So, in general, the practical use of depth-of-field can be summed up as:
- To maximise your depth of field so more of your scene is sharp, use a lens with a shorter focal length (wider), set it to a small aperture and don't stand too close to your subject.
- To minimise the depth of field so only a small part of the scene is sharp, use a longer focal length, set a wider aperture (small f number) and move closer to your subject (if possible).