So you have these two parameters, shutter speed and aperture size, both of which do essentially the same thing: control how much light gets in.

现在你已经了解了这两个参数——快门速度和光圈大小，他们从本质上来说有同一个功能：控制进入相机的光线总量。

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The size of the aperture not only affects how much light reaches the sensor, but also how much of the image is in focus.

光圈的大小不仅影响感光程度，同时还影响在对焦范围的大小。

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Each number does not necessarily correspond to a specific size of the aperture opening, but is a relative number.

每组数字并非是光圈打开大小的特定值，只是一个程度的相关体现。

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By combining the observational power of six 5-inch aperture telescopes spread over hundreds of feet, the NPOI is able to measure the size of stars down to one milliarcsecond on the sky.

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