放大镜和望远镜的放大倍数也都是依照这个标准距离来确定的。
The magnification factor for magnifiers and telescopes depends on the reference distance.
光线（特别是白天的自然光）的强度可以降低眼睛对放大倍数的要求，有时只要有足够的光线，就没有必要再使用放大镜。
The presence of a lot of light (mainly white daylight) can considerably reduce the magnification required. Sometimes, good lighting alone can make reading possible again.
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