"Black pearl" is a Cantonese colloquial expression to refer to someone who has a darker skin and a beautiful face. Some years ago, the Popular Photography magazine had an article giving out tips on photographing a group with dark skin-coloured people in it. If I was not mistaken, it advises arranging those persons to the center of the front row, metering them or metering the persons with lighter skin tones while compensating the light loss on the darker faces with fill-in flash.
But if there is no flash and the environmental light is minimal, one has to pray for luck. Just as now the sky here has turned very dark after lunch, we have to pray for luck for the coming few days of the Easter holiday. But the weather forcast says that we will have tunderstorms until Monday.