- Exposure: From Snapshots to Great Shots
- Understanding Exposure: How to Shoot Great Photographs with Any Camera
- Master Photo Exposure
The basics of using a camera to take pictures start with this, the exposure triangle. It is step one in understanding how photography works.
As with any triangle, there are three main elements that interest us: ISO, shutter speed and aperture. In order for your camera to produce a photograph, it must allow light to pass through the lens and be exposed onto the sensor. So the first element met by light on its way to your sensor is the aperture. It works a lot like the iris of an eye and you can use cats to understand it better. Look at how big the iris of a cat is in low light, and observe how you can barely see it in powerful sunlight. That's exactly how the aperture works. If there is too much light in front of the camera, it will close down. If you want to get as much of it in there, the aperture must be open all the way.
The shutter is next in the light's trajectory. The faster a shutter opens and closes, the less light will enter the camera's darkroom and finally fall on the sensor. You want to use a fast shutter speed in powerful daylight or when shooting in a studio. A longer period between the opening and closing of the shutter will allow a lot of light on the sensor and this is called a long exposure. It is generally used in low light conditions or whenever the user wants to achieve certain silky motion effects.
The ISO sensitivity (or ISO speed as you might also encounter it) is the sensitivity of the sensor to light, which can be changed from very low to very high. The lower the sensitivity, the lower the numeric value will be. You will want to use a low sensitivity for outdoor shooting and studio lighting and a higher sensitivity for shooting in lower light situation.
Here is photographer Mark Wallace with detailed explanations in this video from Adorama TV.