Light is energy, and cinematography begins with understanding how that energy behaves. All radiative energy exists on the electromagnetic spectrum, from harmless radio waves to lethal gamma rays. Nestled between ultraviolet and infrared lies a very narrow band we can see—the visible spectrum. This tiny slice, measured in nanometers from roughly 400 to 700, is the only portion of the spectrum available to cinematographers. Everything we do with light begins there.
Color, in practical cinematography, is inseparable from temperature. Color temperature describes the relationship between heat and the color of light emitted by a theoretical “black body radiator.” As thermal energy increases, emitted light shifts predictably from red to orange, yellow, white, and finally blue. This relationship is measured in degrees Kelvin, a scale developed in the nineteenth century by Lord Kelvin. A toaster coil glowing red, a candle flame, and the sun at midday all obey the same physics—they simply exist at different points on the Kelvin scale.
For most of film history, movie lighting relied on incandescent filament lamps. These tungsten sources produced a continuous, predictable color spectrum at approximately 3200K, regardless of wattage. For decades, cinematographers shaped color using gels, dimming lamps to warm them or adding blue filtration to cool them. It was an intuitive, physical process, and for many years, it worked remarkably well.
As filmmaking moved increasingly outdoors after World War II, the need for powerful daylight-balanced sources led to the use of carbon arc lamps. These fixtures produced intense 5600K light by igniting carbon rods with massive electrical current. They were bright, beautiful, and extremely labor-intensive, requiring constant adjustment, dedicated generators, and careful handling. While many cinematographers loved the quality of light, studios did not love the cost.
That problem was solved in 1969 with the invention of the HMI (Hydrargyrum Medium-Arc Iodide) lamp. HMIs delivered daylight-balanced output without the drawbacks of carbon arcs and quickly became indispensable. They remain widely used today, particularly when large amounts of “punch” are required. Although not a continuous-spectrum source, HMIs provide reliable daylight output and are critical during the frantic hours as daylight fades—what some call “magic hour,” and others know as organized chaos.
Fluorescent lighting marked the next major shift. For years, filmmakers struggled to shoot in practical locations lit by commercial fluorescent fixtures plagued by green spikes, flicker, and poor color rendering. In 1987, Kino Flo introduced high-quality fluorescent tubes designed specifically for cinematography. With improved CRI, flicker-free operation, and remote ballasts, these fixtures transformed how sets were lit. They allowed cinematographers to work softly, efficiently, and invisibly, helping usher in the naturalistic lighting style common today.
The most dramatic transformation, however, has occurred in the last decade with the rise of LED technology. Once crude and unreliable, modern LED fixtures now offer high CRI, full RGB control, programmable effects, and extraordinary efficiency. Incandescent lamps—95 percent heat, 5 percent light—have nearly vanished from sets. LEDs are cooler, faster, and endlessly flexible, expanding the creative toolkit of cinematographers at an unprecedented pace.
Light and color have always been bound by physics. What’s changed is the speed, precision, and control with which we now shape them. Understanding where these tools came from—and why they behave as they do—remains essential to using them well.