在睡前灯光越暗越好，最好是一点灯光也没有，用一些黑色的窗帘阻挡灯光，替换所有会吸光的东西，如会发光的钟。
Use blinds or blackout curtains to keep out light. Switch off or cover anything that emits light, such as an alarm clock.
但是，黑色素的吸光度下降迅速，到光谱红端它几乎什么都不能吸收了。
But, melanin's absorbance falls down so rapidly that by the infrared end of the spectrum its hardly absorbing anything at all.
黑卡，就是一般的纸，重点是要黑色，黑色会吸光，如此相机才不会拍摄出这片卡的颜色。
A black card is just a regular cardboard paper. The key point is the color black. Black absorbs light. Therefore, the camera will not capture the black card.
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