I know this part isn't technically an exercise, but I feel it is important nevertheless to understand this section and I am sure over the next few weeks, months, years even, it will be paramount to my photography, so it seems appropriate placing it at the start of my blog.
(Aperture) f-stop numbers and light reaching the sensor/film.
Light reaches the cameras sensor through the lens and the amount of light getting through can be controlled by adjusting the size of the hole (aperture).
Aperture is measured in f-stop numbers, sequencing as follows:
f/1.4 - f/2 - f/2.8 - f/4 - f/5.6 - f/8 - f/11 - f/16 - f/32 - f/45.
Each step to a lower number doubles the amount of light passing through the lens, each step to a higher number halves the amount of light passing through. (range of apertures are subject to what the lens is capable of).
For example, a small f-stop/aperture number (e.g. f/2.8) is a large aperture. A large number (e.g. f/32) is a small aperture.
Changing the aperture affects shutter speed, which in turn affects motion blur and is key to controlling depth of field.
Big number = big depth of field (DOF).
Small number = small depth of field (DOF).
How shutter speed controls the light.
This is another way (as well as aperture) to control the amount of light reaching the cameras sensor/film. Aperture allows you to control and adjust how much light is coming through the lens but to correctly expose the shot, you must also adjust the amount of time the sensor/lens is exposed to the light. This is what the shutter speed controls.
So for this to be correct and to have correct exposure of the shot, or to control the exposure to under or over expose a subject to whats required, the shutter speed must be adjusted to suit the aperture.
A wide aperture will require a faster shutter speed for correct exposure.
A small aperture will require a slower shutter speed for correct exposure.
Now to place this into practice with the relevant exercises!
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