Tungsten or LED fixture integrated into the scene as practical light — table lamp, overhead fixture. Motivates fill and key without looking constructed.
You place a fixture in the frame that has to be there — a bedside lamp next to the bed, a floor lamp in the corner, a ceiling light over the dining table. This is the Natural Lamp. It only works if it makes dramaturgical sense, if the viewer accepts it as part of the scenery, not as set lighting. That's why you work with Tungsten (3200K) or modern LEDs in this color range — the color temperature must match the environment, the interior, the time of day.
On set, the Natural Lamp is your silent tool: you position it so that it supports the main lighting concept without looking like you put it there for that purpose. The lampshade directs the light, dictates direction. Often, you don't even need it as the primary light source — it's the motivator, the reason light is coming from there. A scene in the living room at night: the table lamp is on, casting a warm pool on the couch. You feed that pool with additional units, but the lamp itself remains visible and believable. The viewer's eye doesn't ask: Where is the light coming from? It sees: Ah, the lamp.
Practically, this means: RGB LEDs in the lamp itself are often better than Tungsten bulbs because you can avoid flicker and control intensity without risking color shifts. But the optics have to be right — a cheap lampshade destroys the effect. You might put diffusion inside, build in a reflector, angle the fixture to support the key light concept. In harsh scenes (offices, modern lofts), the Natural Lamp can also be cool (LED 5000K), but then the entire lighting design must be cool — otherwise, it looks disjointed.
The common mistake: installing Natural Lamps too bright or too visible. They should illuminate, yes, but not dominate. Often, a 15 or 25-watt equivalent LED is enough, further dimmed by set dressing. In the edit, you'll later notice if the placement worked — conversely, the lamp must also match the key camera positions. If the camera is in front, the Natural Lamp will glare at you. If it's from the side, it gives you side light and a warm background. You decide this before shooting, not after.