Dew Bow
露水弧
"Dewdrops...are large enough so that the bizarre, hyperbola-shape dewbow seen lying on dewy grass after sunrise shows all the rainbow's colors. The hyperbola results from the flat ground intersecting the 42°-radius cone of the rainbow, the apex of which is at your eye. If the dew lasts well into the day, the dewbow will become a parabola and then an ellipse as the Sun gains altitude." Schaaf
露珠...足够大，使得在日出后 lying on dewy grass 上看到的奇特的双曲线形状的露弧显示出了彩虹的所有颜色。这种双曲线形状是地面与彩虹的42°半径圆锥体的交线所形成的。彩虹的顶点位于你的眼睛处。如果露水持续到白天，露弧将逐渐变为抛物线，最后变为椭圆，因为太阳高度角逐渐增加。Schaaf
One of the best ways to see a dew bow is in a spider web on a foggy morning. The image above was captured when the sun came out after a cool foggy morning when droplets had condensed on the spider webs in the area. The colors are enhanced in the photo above, but the steps taken to enhance them also contain some elements of the physics of color. The web was about 20cm across and was photographed from a distance of about a meter.
要观察到露珠弓，最好的方式是在雾气弥漫的早晨观察蜘蛛网。上图是在一个凉爽的雾气弥漫的早晨，太阳升起时拍摄的，当时区域内蜘蛛网上的水滴已经凝结。图中颜色被增强，但增强过程也包含了一些颜色物理的元素。蜘蛛网宽约20厘米，拍摄距离约为一米。 This is the dewbow as photographed. Finding the dewbow involves understanding that a rainbow is formed around the anti-solar point at about 42° and that the conditions are the same for the dewbow. As in searching for a rainbow in a waterfall, you look for the shadow of your head and then position that shadow so that the droplets are out at an angle of 42° from the head shadow. As I positioned my head to see the rainbow colors, they were very subtle - colors that you would notice only if you were looking for them. Since the colored pattern of the rainbow does exhibit some polarization, the colors can be enhanced slightly be using a polarizer on the camera lens. The above photograph was made through a circular polarizer which was rotated to make the rainbow colors slightly more prominent. The moderate enhancement of the colors of the top photograph made use of the fact that much of the light coming from the spider web as reflected and scattered light is essentially white light, or an essentially equal mixture of all visible wavelengths. Increasing the saturation of the light basically has the effect of subtracting out part of the broad-spectrum white light, so will make the colors more evident. The colors in the top photograph were moderately enhanced by increasing the saturation and by removing some emphasis on the brightest and darkest pixels.
这张照片是雨后景象。寻找雨后景象需要理解，彩虹是在大约42°的反太阳点形成的，且形成雨后景象的条件与形成彩虹相同。正如在瀑布中寻找彩虹一样，你应寻找自己头部的影子，然后将影子定位，使水滴以42°的角度偏离头部影子。当我将头部定位以观察彩虹颜色时，这些颜色非常微妙——只有在刻意寻找时才能注意到。由于彩虹的彩色图案表现出一定的偏振，使用相机镜头上的偏振片可以略微增强颜色。上述照片是通过圆形偏振片拍摄的，偏振片被旋转以使彩虹颜色更加突出。顶部照片颜色的适度增强利用了这样一个事实：来自蜘蛛网的许多光是反射和散射的白光，或基本上是所有可见波长的混合。增加光的饱和度基本上相当于从广谱白光中减去一部分，因此会使颜色更加明显。顶部照片的颜色通过增加饱和度和减少最亮和最暗像素的强调而得到了适度的增强。 |
