Other Useful Links & Definitions

Here are some other great links that describe technical camera functions in a somewhat simplistic way.
Lens Elements & Image Quality
Camera Metering & Exposure
Understand Depth of Field



Aperture
The aperture is the lens opening. It controls the amount of light coming into the camera.
Light passes through the lens opening to reach the sensor. The aperture is adjustable, it can be opened wide to let more light in, or closed down to keep out light.
F-Stop is the measurement of the size of the lens opening. The larger the f-stop the smaller the lens opening. The smaller the f-stop the larger the lens opening.
A change of one full f-stop on either side means doubling or halving the amount of light passing through the lens. F8 allows twice as much light through as f11, and half as much through as f5.6.


Depth of Field
Depth of field refers to the zone of focus in a photograph or the distance between the closest and farthest parts of the picture that are reasonably sharp.
Depth of field is determined by:
Lens Opening: The smaller your aperture, the greater the depth of field.
Distance: The greater the focus distance (from camera to subject), the greater the depth of field.
Focal Length: The longer the focal length of the lens, the smaller the depth of field. A telephoto lens produces an image w/less depth of field than a wide-angle lens (assuming the same aperture and focus distance).



The Shutter
1. A shutter sets the amount of time for which film is struck by light.
Shutter speed (how fast the shutter opens and closes)
Use the faster (or shorter) shutter speed when there is a plenty of light
Use the slower (or longer) shutter speed when there is less light.

2. A shutter affects the amount of movement rendered in the image
The longer the shutter speed the more movement you are going to get.
The shorter the shutter speed the less movement you are going to get. (you can even stop something in midair).

Here are a list of usual shutter speed options: 1,2,4,8,15,30,60,125,250,500,1000
1 stands for 1 full second; the other numbers represent fractions; 2 means 1/2 second; 125 is 1/125 of a second; and so forth.
Each setting doubles the time of the setting on one side of it and halves the time of the setting on the other side.
“4” represents half as much time, so allows half as much light to reach the film, as “2”.


Light Meter: A light meter measures light and translates that measurement into a workable set of f-stop and shutter-speed combinations, appropriate to the lighting conditions of the subject. As such, it is a guide to using the three exposure controls: lens opening, shutter speed, and film speed.


Combining the Controls
F-stop and shutter speed have a reciprocal relationship. If the shutter speed is slowed down (to allow more light to reach the film), the f-stop must be closed down (to let less light strike the film) to make an equivalent exposure. The smaller the aperture, the slower the shutter speed.
Different combinations can give you the same exposure. F16 at 1/30, is the same as f11 at 1/60, is the same as f8 at 1/125.

In effect, the choice of exposure is a trade-off between maximum depth of field and minimum image blur. The exposure choice is made according to the needs of the particular picture. If a lot of depth of filed is needed, use a smaller aperture. If a fast shutter speed is important to stop the action, choose a larger aperture and sacrifice some depth of field.