What are shadows in a photo?
The light shines in all directions from a small point source and moves outward in straight lines.
A small light source such as a naked lightbulb or candle produces a hard-looking light with deep shadows and sharp edges.
The sun is a bright sky has a similar effect as its great distance makes it appear as a small spring.
Small lamps and torches may also produce similar effects. This is a helpful exercise to try yourself with the help of a small desk lamp or similar.
Only the parts of the subject directly within the luminous path are illuminated. Anywhere else stays in the dark. But watch what happens when you put tracking paper into the light beam.
The tracking paper passes the light but diffuses it as well. The light that passes through the paper scatters in new straight lines moving in all directions of each part of its large surface. The object you are lighting now projects a softer graduated shade, and the bigger your diffusing material, the harder and more contrasting the shade becomes. This is because the light of a large area cannot be completely blocked by the subject; most of the formerly dark parts now receive at least some illumination. The same occurs with sunlight on a cloudy day; clouds act like diffusers, spreading the light source over a larger area.
It is very important in practical photography to recognize the difference between direct, hard, and soft lighting, scattered lighting, and all the stages in between.
Shadow qualities have a major influence on the appearance of subjects and scenes.