世界本是彩色的,而摄影术在一开始却是以黑白面目示人,因此,用彩色来记录、再现彩色的世界,是摄影术早期的一个大梦。1840年,英国人约翰·弗雷德里克·威廉·赫舍尔爵士(Sir John Frederick William Herschel, 1792-1871)把色彩显影在外层为感光氯化银的纸上,但是无法最终固定色彩,即使在微弱的光线下,它们最终还是变黑了。这就是我们现在熟悉的蓝晒法,或称氰版印相法
By 2004, the occupied and disturbed land area had reached 3.393 million ha by mining, of which forest land took 532 000 ha; In addition, mining also caused 3.72