Exposure is the most important concept in photography. Correct exposure means getting your pictures exposed the way you want them to be exposed.
- Too bright is overexposed
- Too dark is underexposed
- You shouldn’t have parts of the image burned out (no detail)
- Whites need to appear white in whatever lighting you’re using
Your camera uses a built-in light meter to determine proper exposure. The light meter senses the overall brightness in the scene and adjusts the camera's settings so that it exposes for 18% white.
Unfortunately not all scenes are 18% white. As a result, a winter scene with lots of snow will have grey snow and an image with lots of dark shadows will have grey shadows.
You can fix this problem in two ways:
1) Zoom in on your subject, lock your exposure (AE lock), zoom out and take the picture
2) If your subject is too far away you can use an 18% grey card to set your exposure
Don’t forget that you are always in control of exposure. Some images might be more interesting if underexposed, increasing the contrast between light and dark. Some images may look better when overexposed, leaving the viewer with only a few key details to focus on.
When taking a picture you have 3 choices to make that affect exposure.
1) Spot, center-weighted, or evaluative metering
2) Exposure compensation setting
3) Whether or not to use auto-exposure-bracketing (AEB)
Spot or partial metering: reads a small spot within the centre of the frame, disregarding the rest of the scene. This is good for scenes with strong backlighting.
Center-weighted metering: places emphasis on the central portion of the image.
Matrix and evaluative metering: subdivides the frame into small sections, then use software to evaluate the results. This is the default metering mode.
To make an image brighter with exposure compensation: Hold down the Av+/- button and turn the scroll dial to the right, towards the positive numbers.
To make an image darker with exposure compensation: Hold down the Av+/- button and turn the scroll dial to the left, towards the negative numbers.
After taking your pictures, return the exposure compensation to 0 so that the next images will not be affected.
Auto Exposure Bracketing: Takes exposure compensation a step further by varying the exposure automatically with three shots. The first shot is standard, the second one is underexposed (dark), and the third is overexposed (bright).
To set AEB, go to the menu, select the second camera settings tab, select AEB, then press the SET button. Use the left and right arrow keys to set the AEB amount.
AEB works best with continuous shooting. Just hold down the shutter and the camera takes the 3 pictures. Make sure to use a tripod if you are planning to use the images for HDR processing.
You can also use AEB with the drive mode set to single shot. Just take three pictures in a row and the software will do the rest.
Now that you understand exposure it's time to focus on two of the important elements that determine exposure, shutter speed and aperture.