Exposure: understanding shutter speed and aperature

Rembering that pictures are actually representations of light will help you understand why balancing the amount of light is so important. Overexposure is the result of too much light being capture. The photograph will be washed out and indistinct. Underexposure is the result of not enough light. Images will be extremely dark. Optimum exposure will give you a photograph with rich colors and vivid details. The three main things to pay attention to (camera-wise) when setting exposure are:

1. Shutter speed (you might see camera literature refering to "ss")


2. Aperature (f-stop)


3. Light meter

In keep this lesson from being too long, I will cover the first two and save light metering for its own day.

1. The numbers on your dial represent the shutter speed--the length of time that the shutter opens to allow light to reach the film. They will read something like 1, 2, 4, 8, 15, 30, 60, 125, 250, 500, and 1000. (many newer, higher-end cameras will go even higher.) these numbers are actually not whole numbers, but are fractions of a second. Thus, 1 is a second. 2 is 1/2 of a second. 4 is 1/4 of a second. These number sound quite small, but are actually a long length of time to expose film to light on an average day. Each consecutive shutter speed lets in one-half the previous amount of light (more than or less than, depending on which way you're moving). Thus, 1/60 lets in twice as much light as does 1/30.

(Notice the subject is backlit--the light meter adjusted for the bright exterior with the result that the subject is underexposed.)

2. The lens will have a ring close to the camera body with more numbers stamped on it. These numbers correllate to the size of the aperature and will read something like: 22, 16, 11, 8, 5.6, 4, 2.8, and 1.4. (some lense will not have numbers all the way down to 1.4, but that's due to the mechanical properties of the particular lens.) The largest number corresponds to the smallest opening. This is, again, because they are fractions. Think of it this way: 1/22 is definitely smaller than 1/4. Simple! Just like the shutter speed functions, one f-stop is exactly one-half the amount of light as the previous f-stop. So, if you were using an f-stop of f/11 and needed to let in less light, f/8 would be axactly half the amount. Going from a larger aperature to a smaller on is called stopping-down.