Understanding Exposure

If you want to venture out of your camera’s auto mode to have more control over your images, one of the most important things to understand is exposure, which determines how light or dark your photo will be.

If your camera doesn’t let in enough light, your photo will underexposed and you won’t see things very well. If you let in too much light, your photo will be overexposed – it’ll be too bright to see details. Your goal is to achieve perfect exposure by balancing three main elements: ISO, aperture, and shutter speed.

  • ISO is the measure of the camera sensor’s light sensitivity.
  • Aperture is the opening in a lens that can be adjusted to let more or less light hit a digital camera’s sensor.
  • Shutter speed is the amount of time, expressed in fractions of a second, that the shutter is open to let light through the aperture.

ISO, aperture, and shutter speed all work together. These settings can help you achieve certain creative effects, but you have to keep in mind that if you adjust one setting, the other two will be affected. You’ll have to adjust all three in order to maintain perfect exposure. Refer to the chart below to see how they affect your photos.

 
 Exposure cheat sheet. Aperture, shutter speed, and ISO settings for digital photography.
 

Your DSLR should have a light meter to gage your exposure. If your meter is at 0, your photo is perfectly exposed; -2 is underexposed, and +2 is overexposed.

If your pictures are too bright, try upping your shutter speed, increasing your aperture, and/or reducing your ISO. If your pictures are too dark, reduce the shutter speed, decrease your aperture, and/or increase the ISO.