底光是刻意的：光源压到低位、偏右，先照亮下巴底、脖子和锁骨，脸的上半留暗，再加闭眼低头，气氛一下就静下来。底光很容易搞成恐怖片，关键是别太硬，边缘留一点滚落。
analog film portrait, photorealistic raw film scan, low key chiaroscuro,
one young Chinese woman, pale skin, long black hair falling over her left shoulder,
a jade hairpin in her hair,
a crinkled white silk pibo covering her head and draping down over her right shoulder,
sheer fabric catching the light, a soft flowing edge,
eyes closed, head tilted slightly down, lips faintly parted, a calm serene expression,
a faint beauty mark, bare skin, minimal makeup,
warm soft light from below and to the right, illuminating the underside of the chin,
the neck and the collarbone, the upper face and left side falling into deep shadow,
a thin golden rim light along the edge of the silk,
a deep blue-black background with no visible set,
close-up, head and shoulders, vertical composition,
shot on a 6x7 film camera, 105mm f/2.4, warm 800 speed film pushed one stop,
heavy grain, warm orange-brown grade, crushed blacks, soft highlight roll-off on skin,
fine facial hairs catching light, natural skin texture, fine art portrait, meditative mood
底光要是太亮，把 warm soft light 换成 faint warm light，暗部会更沉。