How is a photograph “Exposed”?
How you expose an image is everything in photography. If your images are too light or too dark, you lose a lot of the information that makes a good photograph.
In the “old days” light reacted with the chemicals on the film surface to create your image. Today an exposure is an image recorded on your camera’s sensor. It’s called an “exposure” because the sensor is being exposed to light from outside the camera.
To get the correct balance of light and dark, the right amount of light has to reach the sensor. This is typically done by combining an appropriate aperture and shutter speed. They both control the amount of light that enters the camera. When they are combined in the correct proportions for the amount of light available, you will get a correctly exposed image.
The aperture is the opening in your lens through which light travels to the sensor. The shutter speed is the length of time your shutter stays open to allow light in. If the size of the opening increases, and is for a longer period of time (slower shutter speed), the image will be lighter.
When an image is too light, we call it an “overexposure.” Either the shutter was open too long, or the aperture we picked was too large. Too much light hit the sensor, and the image is too light, with no detail.
Underexposure is the exact opposite of overexposure. It’s what happens when too little light hits the sensor and the resulting image is too dark. This usually happens when your aperture is too small or when your shutter speed is too fast. In most cases, underexposure is tied to an overly fast shutter speed. If you take a picture at 1/2000 sec, for example, the image sensor doesn’t get much time to receive the light. The image left behind is so dark that you can’t see many details.
The amount of light entering the camera depends on aperture size and shutter speed.
A larger aperture number means a smaller opening, less light entering the camera, and more of the image in focus.
A smaller aperture number means a larger opening, more light entering the camera, and less of the image in focus.
A slow shutter speed (1/8 sec.) lets in more light than a fast shutter speed (1/500 sec.)
A faster shutter speed (at least 1/125 sec.) is required to stop action
An overexposed image has received too much light and is too light.
An underexposed image has not received enough light and is too dark.
Paying attention to how you use these components should help improve your photography.