| Exposure (ISO, f-Stop, Shutter Speed) |
| There is a set of three basic settings that control exposure levels and it is important to learn how to use each one separately and together. They are ISO, Aperture (f-stop), and Shutter Speed. ISO (ASA) This controls the light sensitivity. A roll of film can only have one ISO setting while digital cameras allow you to select from a list. Select a low number for bright sunlight and higher numbers for low light. The standard settings are 50, 100, 200, 400, 800, 1600, etc. Each increase from 100 to 200 to 400 etc, doubles the amount of light. However, higher numbers also cause the photos to appear grainy with lots of noise. Aperture (f-stop) This is the size of the opening inside your lens. The numbers is actually a fraction of 1 over the number and is computed by dividing the length of the lens from the size of the opening. This is why longer lenses need to also be wide. Some of the cheaper long narrow lens only open up to 5.6 f-stop. The standard stop settings are 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22 etc. Each increase cuts your light in half. Each decrease causes your depth of field (DOF) to be smaller. Shutter Speed This controls the length of time the camera sensor is exposed. Longer time gives you more light. Less time stops motion. The shutter speed is a fraction of 1 over the number you see displayed. The standard shutter settings are 15, 30, 60, 125, 250, 500, 1000, etc. Monitoring Exposure There are two methods to monitor the exposure level of each photo. They are the histogram and the light meter. Histogram That little graph in your camera’s display is your friend. Learn how to use it and understand it. The most important thing you need to know is you never want any part of the graph all the way to the right or left side of the chart. Your goal is to have the graph to the right side of the center. Light Meter This is the bar at the bottom of your view finder. This feature will only work in full manual mode. However, it is not very useful while using a flash. Setting Change You may need to change the setting because of motion blur or you want to change the DOF. For example, you had motion blur using the setting ISO 200, f/5.6, and 1/60. If you double the speed to 1/125, that would also cut your light in half. You now need to change one of the other two settings to correct the exposure level. You can use ISO 400 or f/4 to double your light. |