youdao

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。

youdao

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。

youdao

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