Exposure is the combination of the intensity of the light that reaches your camera’s sensor. This is controlled by your aperture (f/stops) and also by your shutter speed.
Your Aperture (f/stops) is the size of he opening of the iris that lets light into your camera. As the opening gets larger, smaller f/stop number the more light enters your camera.
Each f/stop represents a doubling or halving of the exposure. Going from f/stop 2 to f/stop 2.8 means that twice as much light is entering your camera.
When you have time, use your camera’s histogram to make sure your scene is exposed correctly. However if you are in a hurry, use your camera’s EV bar in your viewfinder.
Set your camera to Manual Mode and you will be able to control the amount of light that enters your camera by adjusting both your Aperture (f/stops) and your shutter speed.
For a properly exposed photograph you want your indicator right at the middle. If you go too far to the right the image will be over exposed and may looked washed out. If you go too far to the left your image will be underexposed and will look very dark. Remember that if you control your EV bar with your aperture, the more light you let into the camera (lower f/stop number) the less depth of field you will have.
If you have a low light situation or are shooting a scene and want to make sure to expose the photograph correctly you can bracket your shot.
Bracketing means that you will shot a photograph at the correct exposure your EV bar is telling you, and then shot another photograph of the same scene one stop lower or one stop less. This is bracketing manually.
***Do this in Manual mode otherwise your camera will compensate by adjusting your shutter speed for you to expose the image correctly***
Your camera should also have an Exposure compensation button that you can use while your camera is on Automatic (be that Aperture Priority or Shutter Priority).
Refer to your manual and find the EV compensation button, it should look like a little plus or minus sign. Press it then you can then use your scroll wheel to move over expose or underexpose the image. Also check your manual as to what modes EV compensation (bracketing) will work. For the most part EV will not work when you are using a flash (Bulb) or in Manual Mode. Also check to see how you can turn this off. In my camera I have to hold down the EV compensation button will pressing the green button, turning off my camera will not turn this mode off, but each camera is slightly different.
Another way to bracket is to tell your camera to bracket for you.
Your camera should have a the option to bracket. Check your manual to see what your camera calls it. It may be referred to as just Bracketing or Exposure Bracketing.
Your camera should have a bracketing button. It’s 3 overlapping rectangles one gray, one white, one black.
Press this and you can use your dials to set the number of frames you want to bracket and how many stops you will bracket.
The image to the right has 3 frames set to bracket. One at the correct exposure and one half a stop underexposed and one half a stop overexposed.
Bracketing helps you make sure that you get well exposed photograph. You can meter your photograph and then bracket the photograph to be on the safe side. Once you understand how exposure works you can then choose to overexpose or underexpose and image for effect. Like the image below taken by Jack Delano.