Black can be the most beautiful of colors you can photograph.
Black is also your single biggest roadblock to getting the right exposure in your picture.
A black-dress on your subject, the blackness of night, nothing but black in your frame - each is guaranteed to freak out your camera's light-meter - 'too dark! make bright!!' it screams. And then it promptly over-exposes your photo, attempting to bump-up the overall tone of your photo to gray.
This is because camera light-meters are built to reliably do just that : expose every time to get a gray tone. Too much black in your frame, and they overexpose; too much white in your frame, and they underexpose - all so that they eventually end up with gray.
So 'bye-bye' to all-black photos?
'Not so fast Light-Meter!' you can say, after you set your shooting-mode to the magical 'M' (Manual) marker.
And now you can take the gray-tone business completely out of the game. Here you tell your camera to use your dialed in aperture (f-stop) and shutter-speed, and you record on the sensor exactly what you see with your eyes, without any exposure-adjustments by the light-meter.
Then you watch as your camera obeys your command and brings into your snaps, that incomparable of colors - Black!
Happy Photographing!!