Learning about exposure, when taken step-by-step, is actually quite simple! Let's take a look at the basic elements of exposure, or how light or dark your images are:
To fully understand exposure, it's important to know exactly what a camera is and the basics of how it works. There are four fundamental parts to every DSLR:
- A body | Your camera's body is a light-proof box.
- A sensor | This is your DSLR's equivalent to film. The sensor, as illustrated, is an electronic, rectangular piece placed on the inside of the camera's body. The sensor is extremely responsive to light and is cornerstone of exposure.
- A hole | Your camera's hole is placed opposite the sensor. It's through this hole that the light enters the camera body and touches the sensor.
- A lens | The lens is attached to the hole, allowing you to control how much light enters the camera for each picture.
Webster defines exposure as "The state of being exposed to something." It can be helpful to separate this word from the context of photography and consider it's general meaning. When a person is exposed to the elements, for example, he or she is opened up to wind, rain, sun, etc... When a crooked politician is exposed, his deeds are revealed for all to see.
Your camera's sensor is exposed to light every time a picture is taken (the lens opening and closing). How exposed the sensor is depends on how much light comes into camera, which is controlled by the lens!
The goal, then, is to let just the right amount of light into the camera. As you continue on your photography journey, you'll learn how to adjust the size of the hole in your lens (aperture) as well as how long the lens is open for (shutter speed) to correctly expose the sensor.
Below is an example of how varying amounts of light entering the lens will affect exposure:
When you look through your camera's viewfinder, you'll see a strip of analog numbers and symbols on the bottom of the screen. In the middle of these, you'll see a set of small lines, with a "+" and a "-" on each side and a "0" in the middle. This is your camera's light meter, and it's there to tell you whether your image is over, under, or correctly exposed.
When more small lines appear to on the "-" side, it indicates that your image is underexposed. When more small lines appear on the "+" side, it indicates that your image is overexposed. The goal is for no lines to appear on either side, indicating a proper exposure.
Of course there are situations when a photographer cannot rely 100% on the light meter. For example, when taking pictures in the snow or on a bright beach a lot of light will reach the sensor. Your camera does not know that the scene is supposed to be very bright and the light meter will probably indicate that your scene is overexposed. You may have to outsmart your camera in these situations! In less extreme settings, however, your camera's built-in light meter is very reliable.
A properly exposed picture normally has three main features:
- Details in the highlights: Bright areas are not "blown out" and all white
- Detail in the shadows: Dark areas are not solid black
- A range of tones between white and black
Experimenting with exposure is one of the joys of photography. We encourage you to explore the options available on your camera and discover how the built-in tools can help you to create the images you envision.