Fill flash is when you are outdoors for example and the light you are getting from the sun is the main light. Fill flash is just that.

现在来谈谈闪光灯补光，补光是指当你在户外，阳光是主要光源时，闪光灯用来照亮阳光给人物带来的阴影等影响(如兔眼等)。

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This time the flash fires just the right amount of light to "fill-in" the subject with the flash produced light. Now you have a rather nice shot where you can see the subject and the background.

然后你再次拍下照片，闪光灯发出刚够照亮拍摄主体的闪光，这一次的照片要好多了，你可以同时看清主体和背景。

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If the person is within five feet, use the fill-flash mode; beyond five feet, the full-power mode may be required.

如果人物在五英尺内，可使用充分闪光模式，在五英尺外，则需要使用完全闪光模式。

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To get creative in challenging light, a built-in pop-up flash supplies extra lighting when capturing images in low-light situations or to provide a fill flash to eliminate shadows.

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