You can use natural light in its simplest way, Be it a window with a big glass or a direct natural sunlight you can modify it and use it the way you want.
This is a favorite technique of mine and can make some really dramatic portraits. The soft light through the window acts as the perfect highlight for a strong and moody image and works particularly well if you have the light cast on just one side of the subjects face, leaving the other in shadow.
The general rule is that the closer to the window you are, the more light you’ll have to work with and the stronger the contrast. Also, if the light coming through the window is too bright, you can use curtains or a blind to diffuse some of the light.
CAMERA : SONY A7RM2 / 85MM F1.8 | F1.8 | SHUTTER : 1/125 | ISO : 200