To make sure that the cameras are accurately recording small changes in reflected light, engineers look for a bright light against a dark background to provide a reference point.

为了确保相机准确地记录来自反射光的细微变化，工程师寻找暗背景上的亮光，来提供一个参照点。

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The computers needed a strong, clear guiding light to track, as a kind of reference point.

计算机需要强大而清晰的导向光作为一种参照点。

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If I can see the light source, I usually make sure to leave a mark here on a separate layer as a point of reference.

如果我能看到光源，我通常一定要在一个单独图层上留个记号作为层参考点。

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President Obama even made a light-hearted reference to Mr Netanyahu's warning of a "red line" with Iran's nuclear programme.

BBC: Obama limo breaks down in Israel after 'fuel mix-up'

An audience member shouted out "Doc" perhaps a light-hearted reference to Sherlock Holmes's sidekick.

WSJ: Folk Musician Doc Watson Dies

The gift was a light-hearted reference to US Vice-President Joe Biden's recent remark that the new US administration wanted to reset ties with Russia after years of friction.

BBC: Button gaffe embarrasses Clinton