Light source visible in frame that actually works: ceiling fixture, desk lamp, monitor, window. The DoP uses it for illumination and typically reinforces or gels it.
Technical Details
Practical light sources typically operate with wattages ranging from 15 watts (LED bulbs) to 500 watts (halogen spotlights in table lamps). Household incandescent bulbs produce a color temperature of around 2700K, while daylight LEDs reach 5600K. Candles generate extremely warm light at 1900K with a luminous intensity of only 12 lumens. Modern LED strips can be dimmed and their color temperature varied between 2700K and 6500K via DMX control. Screens used as practicals deliver 100-400 lux depending on the content, with an average color temperature of 6500K.
History & Development
The use of practical light sources dates back to the silent film era, when real candles and gas lamps were the only available options. Their deliberate use as a conscious design element developed in the 1940s within Film Noir. Orson Welles systematically employed table lamps and chandeliers as narratively motivated light sources for the first time in "Citizen Kane" (1941). The 1970s brought the breakthrough of dimmable halogen technology, while programmable LED systems since 2010 have opened up new creative possibilities.
Practical Use in Film
In "Barry Lyndon" (1975), Stanley Kubrick exclusively used candles as practicals and developed special f/0.7 lenses for the low-light conditions. Denis Villeneuve utilized over 200 programmable LED panels as practical light sources for a futuristic atmosphere in "Blade Runner 2049" (2017). On set, practicals are often enhanced with hidden auxiliary lights: a 40-watt bulb might be supported by a 650-watt tungsten Fresnel outside the frame to achieve sufficient light output.
Comparison & Alternatives
Set lighting remains invisible and serves purely technical purposes, whereas practicals are always visually present. Bounce light is reflected indirectly; practicals illuminate directly. VFX light sources are added digitally, while real practicals create authentic light distribution and reflections. In low-budget productions, cleverly used practicals can replace expensive lighting equipment. High-budget films combine both systems for maximum control over lighting and atmosphere.