When it's dark, we may bump into things without the help of light.

当天黑时，我们可能会在没有光的情况下撞到东西。

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For example, an edge might be a contrast between values (the difference between light and dark), colors, textures, or even rhythms (repetition of imagery), without the use of line at all.

例如，边可能是属性值(明暗差异)、颜色、纹理乃至规律(图像反复)的对比，完全与线无关。

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Flash or strobe light lets you photograph in dark places without having to increase your camera's ISO setting or use a tripod, as long as the subject is within the range of your light.

有了闪光灯，你就可以不用增加照相机的ISO刻度，或使用三脚架的情况下就可以在暗处拍照，只要拍摄物在闪光灯的有效范围里。

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Obviously at 400 feet it's really quite dark but at the surface it starts off being very very light, even without a mask I can tell that.

BBC: Breakfast with Frost