How to Define Camera Exposure

How to Define Camera Exposure thumbnail
Set the camera mode to "Manual" (M) before determining exposure.

Understanding how camera exposure works is essential when shooting film, as you cannot visually preview the results of your settings. In the realm of digital photography, most cameras have automatic exposure settings, but knowing how to manually override the automatic exposure can help you quickly achieve more accurate results. The following instructions detail how to determine camera exposure according to your light meter's guidance.

Things You'll Need

  • Camera with manual exposure control and built-in light meter
  • Fresh camera batteries
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    • 1

      Purchase fresh batteries for your camera. Older film cameras will still take images with a dead battery even though the light meter will not function properly. Newer film and digital cameras will not turn on at all without a charged battery.

    • 2

      Set the film speed. This is essential for a film camera, as the light meter will misread the amount of light in a scene and incorrectly expose the film otherwise. Older cameras have a dial marked "ISO" or "ASA" with numbers in a range from 100 to 1600. Newer film cameras may have an ISO button that should be pressed while using a scroll button to choose the options displayed in a digital panel. Digital cameras allow you to choose any film speed, though the higher the number, the grainier the image becomes.

    • 3

      Set your camera mode to "Manual" (M) if you have an option to do so. Older cameras are often only manual. Newer cameras have "Program" (P) mode, which denies you control of your camera exposure.

    • 4

      Determine how your light meter conveys overexposure or underexposure. With older cameras, this could be as simple as a needle in the viewfinder that balances between a plus and minus sign when proper exposure has been reached. Other cameras may have a series of dots or boxes that increase toward a plus or minus sign, indicating proper exposure with only one box in the center of the signs. Consult your camera's manual if necessary.

    • 5

      Alter your camera's shutter speed until your light meter indicates that you have reached a proper exposure. This is done by turning the shutter speed dial on older cameras. This dial will feature numbers such as 2, 4, 8, 15 to about 1000. Newer cameras have a scroll that allows you to browse these numbers on a digital panel. As you change shutter speeds, you will see your light meter's indicator light or needle move. Once proper exposure has been indicated, note the resulting shutter speed and aperture combination, and take your picture. If you move your camera even slightly, the indicator may change entirely. Different scenes may need different amounts of light for a proper exposure.

    • 6

      Consider that there is more than just one shutter speed and aperture combination that will work for a given scene. If the meter says that a shutter speed of 1/60 at an aperture of f/8 is the proper exposure, and you want a faster shutter speed of 1/125, you can change it, but you also need to change the aperture to compensate. Therefore, if you let in one stop less light by shortening the shutter speed to 1/125, you must let in one stop more light by widening the aperture to f/5.6. In this way, many combinations are possible, as your light meter will affirm as you change settings.

Related Searches


  • "Photography", 9th ed.; Barbara London, Jim Stone, John Upton; 2008


  • Photo Credit camera dial image by Tanya McConnell from

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