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Understanding depth of field
Depth of field is the amount of the frame that is in focus, a large depth of field such as f22 will keep all or most of the frame in sharp focus, whilst a small depth of field such as f4 will focus mainly on the main subject that you are focusing on.
Depth of field is also effected by the distance that the main subject of focus is from the lens. For example if shooting a subject from a mid to long distance with a large aperture of f4 will produce similar results that a small aperture would produce. Whilst shooting from a short distance will produce clearly visible differences.
On this page there are six identical photographs taken at different points of focus and two different apertures. F4 = Large aperture. More light allowed through the lens. F22 = Small aperture. Less light allowed through the lens. Notice that all three photographs taken at f22 are almost identical, whereas the three taken at f4 are all very different.
For this example I have chosen chess pieces to illustrate the depth of field however the same applies to all subjects alike within the rules of the distance the subject is from the lens.
I have chosen to do this illustration at f4 and f22, most lenses are capable of apertures within this range. However some lenses can stop down to f2.8 and even f1.4 there is one lens that can stop down to f1.0, this is a specialist lens. In addition to this some lenses are capable of using apertures up to f32. f1.0 being a very shallow depth of field whilst f32 is a very large depth of field.
Using depth of field to your advantage.
In each case it can have its use, for example if you are photographing a landscape you may want as much of the frame in focus as possible. Or if you are photographing a person or a flower you may want the main subject in sharp focus but to blur the foreground and or background to draw attention to the main subject. The amount of depth of field that you can achieve will depend on your camera, lens and available light. In low light conditions it may be necessary to use a tripod to eliminate camera shake at slower shutter speeds. In bright light you may have to select a smaller aperture or faster shutter speed to prevent over exposure. Note that changing the aperture will have an effect on your depth of field.
Shallow depth of field (f4) foreground focus
Foreground in sharp focus
Middle ground slightly out of focus
Background out of focus
Deep depth of field (f22) foreground focus
Foreground in sharp focus
Middle and background in relatively sharp focus
Shallow depth of field (f4) midground focus
Middle ground in sharp focus
Foreground out of focus
Background out of focus
Deep depth of field (f22) midground focus
Middle ground in sharp focus
Foreground and background in relatively sharp focus
Shallow depth of field (f4) background focus
Background in sharp focus
Middle ground slightly out of focus
Foreground out of focus
Deep depth of field (f22) background focus
Background in sharp focus
Foreground and middle ground in relatively sharp focus
Please Note: These are guidelines only, there are many variables, and every
situation can differ.
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