Source size → hard vs. soft light
How a light source’s apparent size controls edge softness and shadow transitions.
What it is
Source size is how large the light appears from the subject’s point of view, not its wattage. A nearby bare bulb appears larger than the same bulb farther away. Larger sources create softer light-to-shadow transitions, while smaller sources create sharper transitions.
Hard light from a small or distant source produces crisp cast shadows, sharp terminators, and strong highlights. A terminator is the line where light turns into shadow on a rounded form. Soft light from a large or close source produces blurry cast shadows, a wide penumbra, and gradual form turns. A penumbra is the fuzzy zone around a shadow edge.
Choose one light behavior and apply it consistently. With a small, distant source, cast shadows keep firm edges as they travel. With a broad source, edges soften, contact shadows break up, and strong contrasts blur at their boundaries.
Why it matters
Source size connects cast-shadow edges and form transitions across a scene. Weak control can produce mixed shadow hardness, mushy forms in hard light, or flat, cut-out forms in soft light.
You can check it when
- ✓Describe a reference as having a small, hard source or a large, soft source from its cast-shadow and form-turn edges.
- ✓Keep cast-shadow and form-edge hardness consistent throughout a painting.
- ✓Change a study from hard light to soft light, or the reverse, by adjusting edge softness and transition width while keeping the lighting readable.
- ✓Check that sharp and blurry edges occur only when the setup supports them, such as changes in source distance or overlapping sources.