Inside every lens there is an opening where light travels into the camera. This is known as the camera's aperture. The aperture controls how much light hits the film in film cameras or sensor in digital cameras(from this point on in this article I will be talking about digital but it works the same with film cameras). The smaller the opening the less light travels to the sensor and the bigger the opening the more light travels to the sensor. Now you're probably asking why do I need to know this? Remember knowledge is power, and knowing this gives you the power of controlling the amount of light, which in turn gives you correct exposure and sharper photos when used in conjunction with shutter speed and ISO setting.
You can control the size of the aperture by changing the F-Stops in the camera. Each time your lens opens up one F-Stop, twice as much light reaches the sensor. Now I know this could get confusing but the higher the number the smaller the aperture is and the less light reaches the sensor. This is because the F-Stop number is an mathematical equation. It is not important to remember this equation but here it is. F-Stop = focal length of the lens divided by the aperture opening of the lens. All you have to remember is when thinking of aperture values you really need to think opposite. The higher or bigger the number means less light, the lower or smaller the number means more light.
When purchasing a lens it will let you know what the biggest aperture it has, for example a Canon EF Prime 50MM f1.8 II has an F-Stop of 1.8 as its biggest aperture. F-Stops are written on the lenses and the camera screen as f and a number or f then a / then a number. Now some lenses will have something like f3.8 - 5.6 as in Canon EF-S 10MM - 22MM f/3.5 - 4.5. This means that at 10MM the lowest F-Stop is f/3.5 but as you zoom the lens in the lowest F-Stop will be f/4.5. This is due to that calculation I had told you about before. So as you zoom in with the lens you will have less light reach the sensor.
Now for Dark attractions such as Pirates of the Caribbean the smallest you can get your F-Stop the more light will travel in to the sensor.
Here are two examples
In the Two sets of Photos the first shot taken with aperture f/1.8 second taken with aperture of f/3.8. Since the first photo had a lower F-Stop so it let more light into the sensor and so the Shutter Speed was faster and allowed me to get a much clear shots. The second photo was taken at a bigger F-Stop and let less light in to the sensor which in turn needed a slower Shutter Speed which cause the shot to have camera shake and is blurry.
I love using my 50MM Prime lens to shoot dark attractions because it has an F-Stop of f/1.8. which lets lots of light through.
With attractions and shows that are outside in bright sunlight you can use a larger F-Stop. like in this example.
Since Lights, Motors, Action is held outside, and it was a very sunny day I was able to get great shots with an aperture of f/9.0, which is a high number to let less light to the sensor.
Now the aperture also deals with DOF or Depth of Field
In the next Exposure lesson I will go into detail of Shutter Speeds.