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Why does it matter how much light is let into the lens?” “Well, think about it a sec- ond. If the aperture is wide, it lets in more light. It’s good for close-ups.” “Oh, I see,” Meredith inter-

aperture the opening of a camera lens through which light travels Words to Understand

rupted. “But that isn’t good if you are trying to get a picture of scenery or something. Too much of the picture will be out of focus. So in that case you would want to close the aperture, and let in less light.” Colin laughed. “See, you do get this stuff! And there is something else you have to keep in mind here. That’s deciding what your shutter speed should be.” “Shutter speed?” “Yeah. That is a measure of how long the shutter of the camera is open. The shutter lets light in through the lenses. Shutter speed is another way of thinking about exposure time. That is, how long the film is exposed to light.” “How long is the shutter typically open?” Meredith asked. “Usually, a fast shutter speed—also known as a short exposure time—is somewhere around 1/1000 of a second.” Meredith stared at the camera. “You’re kidding, right?” “Nope,” Colin said. “It’s really that fast. But it could be open for several seconds if the pho- tographer wanted. That would let in a lot of light, but also hurt the focus, because things in the picture might move. The longer the shutter is open, the more light hits the film. In fact, a slower shutter speed often gives a blurring effect to a picture.” Meredith sat back and looked at her brother. “I had no idea this was what you were doing in that class. There is so much to know. I thought taking a picture was easy.”

The hole in the center of these lenses is the aperture, which can be made larger or smaller at the photographer’s choosing.

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