早晚的光线颜色很漂亮，但不容易掌握好。尤其是不容易碰到好的云彩。云较高时，才有机会出现火烧云。这时天空较大的面积的亮度会比较均匀，色彩也较好。如果云较低，就象你邮件中的第一和第三张，则反差很大，太阳附近很亮，而云的后面则很暗，地面就更暗了。这种情况下，如果有一片水面作前景就比较好。因为水面可反射天空的光线，使得画面不至于有太大的黑暗区。测光时，我通常会以需突出的主要云彩或天空为点测的目标，并参考最亮和前景的亮度来决定所需暴光。我在这方面也还在探索中，还需要积累更多的经验。有些摄影师喜欢用渐变中灰镜来调整天空与地面的亮度，效果也不错。这种滤镜上部的密度较大，可将天空的亮度减少1-3挡（不同的镜减光的系数不同），下部则是完全透明的，使地面的亮度不受影响。我没用过这种镜，还没有实际经验。据我观察，云彩的形状有的很上镜，有的拍出来现得散乱，不好看。云彩要突出，后面天空的亮度和颜色很关键。相互间要有一种对比的关系，太接近的话就不好看。例如白云就需要蓝天来衬托，这时偏光镜就可发挥作用。

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