Color Producing LEDs versus Colored Lighting Gels|
Article - January, 5 2016 By LarsonElectronics.com
Color Producing LEDs versus Colored Lighting Gels
Color manipulation is an important feature in commercial lighting systems. In the film industry, there are two ways to achieve colored lighting: RGB LEDs and colored gels. Deciding which method to apply strictly depends on the lighting objectives of the operator and the type of fixtures being used on the set.
This article dives into the mechanisms of both light color manipulation techniques. At the end of the post, individuals can find recommendations for suitability and application.
RGB LEDs produce colored light using the following colors in the visible light spectrum: red, green and blue (hence, the acronym). When combined, the primary colors are capable of producing over 16.7 million different types of colors. Individually, each color contributes 256 different shades; and when multiplied together (256 x 256 x 256 = 16,777,216) the colored diodes have the ability to generate an “unlimited” number of combinations. Unlike a conventional LED that is composed of a single cathode and anode, an RGB LED comes with one anode and three cathodes- one for each primary color.
Traditionally, RGB LEDs rely on a regulator that changes the light’s intensity in order to achieve specific color combinations (also known as dumb RGB lighting). An example of this type of RGB LED fixture includes simple RGB nodes found in ribbons or string lights. During output, the operator will not be able to control the diodes individually in the fixture, and all of the nodes support the same colors. Intelligent or smart RGB lighting supports more robust controls through the use of microcontrollers to process incoming data from the main controlling feature.
To achieve accurate color depictions during output, RGB LEDs utilize specific RGB ratios. For example, equal amounts of green and blue will generate cyan, while yellow is a result of combining equal intensities of red and green. Combining all three RGB colors at equal intensities will generate white; and the quality of that white light highly depends on the accuracy of the RGB diodes. Taking this process one step further, in order to generate light teal (an uncommon and complex hue), green should be at full intensity and blue should be at 80 percent intensity with red completely shut off.
Like RGB LED features, colored gels are used to manipulate light colors in live environments. The material is constructed out of heat resistant, dyed polyester sheets and is applied over the light source during output. It may also be applied over other surfaces where light passes through, such as windows and large transparent panels. Such lighting accessories vary in quality, with inexpensive variants having low tolerance to heat and high quality “tough gels” being able to withstand high temperatures from nearby lighting equipment for filming.
During application, colored gels absorb specific light bands and allow others to pass through the filter. Contrary to popular belief, the optical filters do not add color to the light beam (it removes specific hues). The main issue with using colored gels is that they contribute to light intensity loss (e.g., a Color Temperature Blue [CTB] gel blocks up to 66 percent of light output), especially with dark hues and heavy correction variants. Over time, the quality of the gel degrades considerably and will need to be replaced to maintain optimal levels of correction.
Types of Colored Gels
There are several types of colored gels available in the market today. Below are four gel-based filters that are widely used in the filming sector:
- Color Correction Gels: This type of gel is useful for adjusting a light source’s color temperature rating. The two most common types of color correction gels include CTB and CTO (Color Temperature Orange). CTB can be utilized to convert a quartz incandescent light source with a 3,200K color temperature rating (yellowish) to 5,600K (bluish). A CTO gel has the opposite effect, changing a 5,600K rated light source to 3,200K. These specific color temperature variables (3,200K and 5,600K) are considered to be the most widely used color temperature ratings in the filming sector. To cater to other color temperature ratings, the gels come in various intensities, ranging from ¼ and ½ to full and double.
- Color Effect Gels: Color effect gels, which are mostly found in theatrical settings, change the color of the light- for example, changing a white light source to green or adding a subtle, bright pink tone to a white light source. For accurate results during filming, it is crucial to set the camera’s white balance before applying the desired gel.
- Diffusion Gels: This type of filter is designed to diffuse light beams without adjusting the source’s color temperature rating. Diffusion filters can be made out of gel material or synthetic cloth called “spun.”
- Neutral Density (ND) Gels: ND gels are used to reduce light output without diffusing the light source or changing the light’s color temperature rating. During application, the filter equally absorbs all bands.
Which One is Better?
Both RGB LEDs and colored gels have been around for a long time and are capable of accurate color handling and manipulation. The main difference between the two is the way they process colors. RGB LEDs rely on additive color mixing processes (adding specific hues to achieve the desired color of light), while colored gels use subtractive color mixing (by removing visible bands that are not desirable).
In some aspects, RGB LEDs are limited only to controlling the components in the LED light source. They are not versatile and cannot be applied to other types of fixtures, panels and windows. For such applications, gels are suitable for controlling even natural light sources (sunlight).
A clear and perhaps the ultimate advantage of RGB LEDs is their compact and readily deployable features. The solid-state light source does not take up a lot of space and is not prone to long-term degradation in demanding environments, such as studios and outdoor sets. RGB LED settings can be set quickly and accurately using a digital controller. Hence, there is no need to invest in a wide selection of colored gels, which can be costly to acquire and maintain (as mentioned earlier, gels are expendable accessories that are prone to degradation- even when handled and maintained carefully).
Furthermore, setting up colored gels during filming is a tedious process. This is especially true for shots that require multiple lighting configurations. An operator can easily cut the setup time in half using RGB LEDs by configuring presets before the shoot. With RGB LEDs, there is no need to pause filming and install filters over the light sources.