1. F-stops, Shutter Speeds & More
Exposure
F-stops, Shutter Speeds & More

2. Shutter
In a camera, the shutter blocks all light from exposing the film or digital medium until you press the shutter release button.Then it quickly opens and closes, giving the film a brief flash of light. You can control the length of time the shutter remains open by setting the SHUTTER SPEED.

3. Shutter Speed Scale
A half second exposure is 1/2 STOP darker than a one second exposure.
A 1/125 exposure is one stop brighter than a 1/500 exposure.
A 1/1000 exposure is 1.5 stops darker than a 1/125 exposure.
The longer exposures ( like 1 second ) give much MORE light to the film than a 1/1000 of a second exposure. So even though the number may look bigger, don't be decieved!

4. Aperture
When light passes through a camera's lens, it must pass through an opening called an “aperture". Aperture is a hole that lets in more light when it's wide open and less when it's small. The aperture is similar to the pupil in the human eye. You can control the aperture by setting the “aperture opening", also known as an F-Stop.

5. Aperture Scale
Like the pupil in a human eye, the aperture on a camera controls light. It does so by closing up to restrict light, and opening up to let it through. Lower F-Stop numbers indicate more light.

6. The Effects
Why is the background blurred in the right picture, and sharpest in the left ? Because if the exposure is made with a wide aperture ( like f2.8 ), then objects farther away from the subject are thrown farther out of focus.
So... if the aperture is small (like f22) then objects in the background (and foreground ) will appear sharper. However, since more open-shutter time was required to make the exposure on the left ( 1/4 Second ) the subjects became blurred from motion.

7. The Path of Light
Since the amount of light that reaches your film or memory card (aka your capture medium) is regulated by two factors -- aperture and shutter speed -- the two settings must work in concert to produce a good image.

8. Effects
E.g. Freezing action requires a high shutter speed. However, because having a high shutter speed means the shutter only allows a small amount of light to the capture medium (memory card, film) you must have an aperture that is open enough (low number) to compensate for the little light allowed by the shutter to ensure a good exposure.

9. More Effects
Effects like freezing action can be limited or even eliminated by some environmental factors, such as low light. For instance, in a dimly lighted room, you may be able to capture a good image with still subjects, but if they move, the movement may leave a blur (unless you compensate with a flash).Though opening your aperture wide helps, even the fastest lenses have aperture limits.

10. Using ISO to compensate
Remember, if you’re in a low light situation and you’ve maxed out your aperture, one final move is to use faster ISO -- e.g. move from 200 speed film to the more light-sensitive 400 or 800 speed film (or digital ISO equivalent settings, e.g. 200, 400, 800, etc).