When you have the brush tool selected, pressing the number keys will adjust the brush opacity.

当你已经选择了画笔工具，按下数字键可以调整画笔的不透明度。

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If you have the Brush tool selected, hold down Opt key will quickly activate the Eyedropper tool.

如果你已经选择了笔刷工具，按住opt键可以快速启动吸管工具。

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There are a lot of tutorials out there showing how you can do so by using the Healing Brush Tool.

有很多教程已经教给了你，应用修复笔刷可以修复人物照片。

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You then 'paint' the color back in using a brush tool, restoring the original colors into the areas of the photo that you want to.

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Nasa's Mars rover Curiosity has used its brush tool for the first time to sweep dust off the surface of a rock.

BBC: Curiosity Mars rover deploys its rock brush

That latter tool, the Advanced Healing Brush, lets you paint in corrections, rather than using the round dropper to make tweaks.

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