Basic Photography Aperture and Depth of FieldSource: http://www.illustratedphotogr aphy.com/basic-photography/aperture-and-depth-field
Aperture and Depth of Field The aperture explained• In photography, aperture refers to the size of the opening in the lens of the camera through which light can pass.• The size of this aperture is adjustable in nearly all the lenses that fit digital cameras.• By adjusting the size of the aperture, the photographer can ensure that the correct amount of light reaches the digital sensor during any given exposure.
Aperture and Depth of Field The aperture explained• As such, it is one of the three elements used to provide a correctly exposed image.• The others are the length of the exposure, called the shutter speed, and the light sensitivity of the sensor, called the ISO.• The aperture can be adjusted either manually or, in most cameras, automatically by the camera.• When the diameter of the aperture is changed, a set of blades inside the lens narrow down or open up to allow more or less light to pass through the lens.
Aperture and Depth of Field The aperture explained• The act of narrowing down the aperture is often referred to as stopping down while opening it up is called stopping up.
Aperture and Depth of Field The aperture explained• The number indicates the inverted size of the aperture as it relates to the focal length of the lens.• This is quite a mouthful, and not easily understood, but the point is that the larger the number, the smaller the hole, and therefore, the less light is allowed to pass through the lens.• The smaller the number, the larger the hole, and the more light is allowed to be transmitted.
Aperture and Depth of Field The aperture explained• So, other things being equal, the brighter the light in which the picture is taken, the less light would be needed for an accurate exposure and the bigger the f-number one must use.• Inversely, the dimmer the light, the bigger the hole that is needed, and the smaller the f- number that is selected.
Aperture and Depth of Field The aperture explained• Something interesting happens when the size of the aperture is changed. When it is opened up, and more light passes through the lens, the area which appears in focus on either side of the distance for which the lens is focused becomes smaller.• Picture this: you are taking a portrait picture. You focus the lens on the subjects eyes. Behind him is a tree. If you set the lens at a large aperture (small number) the tree behind him will not be in focus. If you use a small aperture (large number) the tree will be in focus
Aperture and Depth of Field The aperture explained• This byproduct of adjusting the size of the aperture is referred to as depth of field and translates into the depth (or distance) of the area which will remain in focus for a given aperture and focus distance.• The creative utility of adjusting the depth of field should immediately be apparent.• By changing how big a part of the photograph is in focus, you can control exactly which details show up, and which do not, allowing you to lead the viewers eye anywhere you wish.
More about depth of field• The depth of field becomes greater with smaller apertures, and vice versa, that much is true, but things are a little more complicated than that.• Depth of field decreases the shorter the focusing distance, so if you are focusing on a subject that is very close to the lens, you will have less depth of field than if you are focusing on a subject which is far away.
Source: http://www.illustratedph otography.com/basic-photography/aperture-and-depth- field