The document discusses aperture and depth of field in photography. It explains that aperture refers to the size of the opening in a camera lens, which can be adjusted to control the amount of light passing through. A smaller aperture number means a larger opening size and more light. Adjusting the aperture also impacts depth of field, which is the area of the image that remains in focus. A smaller aperture produces a greater depth of field, while a larger aperture gives a shallower depth of field with less in focus behind and in front of the focused subject. The depth of field effect allows photographers to control which image details are clear.

1. Basic Photography
Aperture and Depth of Field
Source: http://www.illustratedphotogr
aphy.com/basic-
photography/aperture-and-depth-field

2. 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.

3. 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.

4. 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'.

5. 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.

6. 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.

7. 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 subject's 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

8. 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 viewer's eye anywhere you wish.

9. 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.

10. Source: http://www.illustratedph
otography.com/basic-
photography/aperture-and-depth-
field