Aperture and Depth of Field

Aperture
Aperture (光圈) is the function of a camera which controls the amount of light collected, and equivalently the brightness at an image point. Technically, the structure itself is known as Aperture Stop. It is a hole or an opening through which light travels.

http://www.whatsoever.hk/my.photo.album/aperture.gif

Aperture is usually expressed as F-stop or Aperture Value, e.g. F2.8 or f/2.8. The smaller the F-stop number (or f/value), the larger the lens opening (aperture).

Depth of Field (DOF)
The Depth of Field is the distance wherein objects from near to far appear to be in focus. It is the zone of acceptable sharpness. For any given focal length, the depth of field varies directly with the aperture selected.

When you desire a great depth of field, i.e. where objects both close to you and far from you are in focus, a small aperture is desirable.

http://www.whatsoever.hk/my.photo.album/1881.Heritage.F8.0.JPG
Location: 1881 Heritage, Tsimshatsui, Hong Kong
Equipment: Kodak Z981
Focal Length: 26mm
Focal Range: Macro
Aperture: F/8.0
Shutter Speed: 1/20-sec
ISO: 100


When you want to isolate your subject, i.e. where your subject to be in sharp focus but the background to be out of focus (a shallow depth of field), a large aperture is desirable.

http://www.whatsoever.hk/my.photo.album/1881.Heritage.F2.8.JPG
Location: 1881 Heritage, Tsimshatsui, Hong Kong
Equipment: Kodak Z981
Focal Length: 26mm
Focal Range: Macro
Aperture: F/2.8
Shutter Speed: 1/125-sec

ISO: 100

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