What you need to know about your camera's exposure settings
Break out of the automatic mode to get better photos
I edit the home A/V and pro audio articles on Crutchfield.com. It's a cool gig for a guy who's been seriously into audio since way before 1974. I started buying records, guitars, and gear with the money I made mowing lawns and delivering newspapers. Now the way I earn my money has changed for the better, but where it goes hasn't changed too much. Just give me the proverbial three chords and the truth. I'll do my best to help you feel it, too.
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One of the most important things you need to grasp in order to become a skillful photographer is the concept of exposure – the creative control of the light hitting your image sensor.
Three settings to coordinate
Aperture is the diameter of the opening that allows light to pass through your lens.You adjust the size of the opening by selecting an “f stop” value. One stop lower than your current setting lets in twice as much light, and one stop higher lets in half as much light. A large opening gives your pictures a shallow depth of field, meaning objects in the background appear out of focus.
At f 2.8, the background is out of focus. At f 22, everything is in focus.
Shutter speed controls the amount of time light is allowed to pass through your lens. If aperture is a water pipe, shutter speed is the amount of time you leave the valve open. To freeze fast-moving objects, use a fast shutter speed. If you want a moving object to blur, use a slower speed (or pan the camera to follow a moving object, and the background will blur).
Sensitivity – Once commonly known as “film speed,” sensitivity is measured in ISO numbers. The higher ISO number, the higher sensitivity. In bright daylight, a camera adjusted to a low sensitivity, such as ISO 100, will make a cleaner image with less “noise” or “grain” than one set to a high sensitivity. Use higher numbers indoors or in low light.
Experiment with the mix
As you may have surmised, these three settings are interdependent. How you choose to mix them is part of the organic process of fine tuning a picture. Yes, your automatic settings will make a "best guess" about what will make an optimal picture, but you might have a different vision of the scene in front of you. That's why it pays to experiment.
CameraSim: A great practice tool
We'd like to introduce you to a simulation tool that will help you better understand the interrelationships of these settings. Jon Arnold's interactive CameraSim is a wonderful tool that enables you to try out changes in aperture, shutter speed, and sensitivity. You can also vary the light level, zoom (focal length of the lens), and distance from the subject. Snap simulated photos, and you quickly see the results you get from various combinations, with or without a tripod to steady the camera. Take a bad shot, and you get a tip on how to improve it. Take a good one, and you get a compliment.
We hope the CameraSim inspires you to put your camera in manual mode and apply what you’ve learned. With practice, you’ll learn how to get the kind of shots you want in any setting. You’ll become a more intuitive and fluid photographer who knows how to make art with a camera.