When you look inside your digital SLR’s viewfinder or at its LCD screen, you see your camera’s internal light meter. It is represented by a continuum that goes from -3 to +3 (some DSLRs have -2 to +2). Depending on your camera, you may see numbers or thick marks that represent the numbers. When the tracking marker hits the dead-center mark of 0, you have found a correct exposure.
To the left of 0 means underexposure (too dark), while to the right of 0 indicates overexposure (too bright). Each +/- number represents a full stop of light. Between the stops are dots or smaller dashes that represent 1⁄3-of-a-stop increments or 1⁄2-of-a-stop increments if you have set up your camera that way.
When you are in any exposure mode other than Manual mode and you point your lens at something and press the shutter release button down halfway, the internal light meter automatically evaluates the scene and the camera selects settings to bring the marker to 0.
If you are using Aperture Priority mode or Shutter Priority mode, your DSLR will let you know when it can’t expose correctly for the setting you’ve selected in combination with the ISO setting and available light in the scene. It will blink until you choose a new setting that the camera can work with.
If you are shooting in Manual mode, you must dial in all settings yourself to bring the marker to 0.
When you are choosing aperture, shutter speed and ISO settings all on your own in Manual mode, use the internal light meter as your guide. Manipulate the settings until the marker underneath the continuum reaches 0. If you are way off the continuum, the marker will flash to guide you. If it flashes on the far left, you are underexposed and need to make adjustments accordingly; either choose a wider aperture, a slower shutter speed or higher ISO. If it flashes on the far right, you are overexposed and need to make adjustments accordingly; either choose a smaller aperture, a faster shutter speed or lower ISO. Be aware that you will not always be able to get a dead-center 0 reading in Manual mode, especially outdoors where light changes; even the slightest change can have an effect. The marker will bounce around above and below the center mark, but as long as it does not go beyond 2⁄3 of a stop in either direction, the exposure should be fine. Keep in mind that your evaluation of proper or correct exposure involves your personal taste and opinion—are you looking for more classical shots or something more creative like darker, moody photos that are a bit underexposed?
You’ve been absorbing quite a bit of information, so now it’s time to get out and shoot. Next up are some simple photography tips and techniques that you can immediately start applying to achieve beautiful results.
0 on the light meter marks correct exposure. To the left of 0 means underexposure (too dark), while to the right indicates overexposure (too bright).