Quality of light refers to the color, and hardness or softness, of light.
In this tutorial you will learn:
Hard light comes from a single, direct source. It produces shadows and sharp lines.
Hard light happens at mid-day or in a room with a single bright light source.
Soft light comes from a diffuse or indirect source.
Soft light happens during sunset or sunrise, or indoors if there are many diffuse light sources.
Compare the pictures below. Notice how the feel of the photo changes depending on the lighting it was shot in.