Color Theory Basics – The Effect of Lamp Type on Color
For the last installment in my series about Color Theory we will look at how Color and the Perception of Color is affected by the source of the light, or the Lamp Type. Anyone who has spent any amount of time working with a mixed package of discharge sources and conventional lights knows that getting them to work together can present significant challenges. Further, the qualities of light (direct vs. indirect or spotlight vs. flood lights) can effect how we perceive the exact same color from the exact same lamp. It is useful to have a basic working knowledge of these ideas so that you can approach your lighting plot from a stronger position.
The Effect of Source.
Most lighting for live performance utilizes Incandescent lights. These are variations on the same bulbs found in any household or workplace. There is some kind of metal filament which is encased in a glass globe. Electricity is passed through the filament and the heat from that is discharged in the form of light. As much advancement as we have seen, these are very simple technologies, and not too far from fire. We burn an object and it creates light and heat. Oldest trick in the lighting book.
Because we are basically operating on the same system as our caveman ancestors, the colors are very similar. These bulbs make a warm soft glow. Our eye is particularly attuned to this range of colors and while the full spectrum of visible light is present in this “White” light, there is a preponderance of light in the Red and Amber range. This makes the light emitted from such bulbs appear “natural” and “looks good” on any range of skin tones.
An alternative to the incandescent bulb is the Discharge Source. A common discharge bulb used in Film, TV, and some live performance is the HMI. Rather than burning a piece (or pieces) of metal, the glass globe is filled with various gasses which, when excited by the introduction of electricity, emit light in rather precise wavelengths. Fluorescent bulbs work this way as well. Depending on the mixture of gasses, the color will be different. Neon is a commonly used gas as are Sodium, Mercury, and others.
How do these work?
Electricity causes a shift in the orbit of electrons around the nucleus of an atom. In these more agitated states, the atoms can absorb some amount of additional electrons. At some point the atom returns to its normal state and the electrons return to their standard orbit. When this happens the extra electrons are released from orbit in the form of photons. The wavelength of the photon (or as our eyes and brain would say, Color) is determined by the type of atom we are dealing with. The Earth’s atmosphere, for example, has a mixture of gasses which, when averaged, produce light in the medium Blue range. As the sunlight filters through the atmosphere, exciting the gasses in our atmosphere, the light emitted from the restored atoms averages out to Blue. Color mixing and physics!
Because the mixture of gasses produce different colors of light, the use of color filters on these lights will produce different effects than when used on incandescent lamps. We commonly see these differences when using Followspots. While the majority of our lighting rig might be incandescent spotlights, the followspots are very likely Xenon, or some other gas. Thus we must balance the color of the spots to blend with the rest of the lighting. The difference in lamp type in these situations is a primary cause of Missing Color Syndrome and a leading need to understand Color Correction. Similar situations arise through the use of many Automated lighting instruments. This is why many will include a CTO option in their color mixing and/or color wheel options.
Not only is the actual color different based on what kind of bulb we have, but the perception of the color can change based on whether the light is direct or indirect, a spot or a flood. Direct light from spotlights are the most common in live performance. Be they ERSs, PARs, Fresnels, or other, all of these lights produce a hard direct light. The light comes, more or less, straight our of the bulb in a concentrated fashion and hits an object. Because of this, the light is seen as being very present. Under certain conditions you can see the geometric shape of the cone of light itself.
Contrast that with floodlights like Mini-10s, Far Cycs, or Mercury Vapor Gym lights, and you see that the quality of light is much softer and more diffuse. We still have the directionality and the hardness, but we lose the geometry. While these can be useful for filling a volume of space efficiently with light, they are not so good for giving that light a clearly defined presence. As the light has less presence so too does our perception of the color. While you might want this effect, it can make colors appear muddy or unclear. You get illumination, but it can be hard to get a real sense of the light itself as an entity.
Taking another step back we have indirect sources like Softlites and Bounce Light. While you can bounce any kind of light off of any kind of surface, typically one uses a spotlight to bounce off a White surface. This is a technique common in Film and TV, but rare in live performance. The quality of light is similar to that of an overcast day. There is illumination, but it is shadowless. The light wraps around and enfolds objects. While it is a beautiful quality of light, one must very carefully consider their color choices here. The light itself is so recessive that getting basic visibility necessitates clear and considered color choices.
While the default choice for most designers is some version of the incandescent spotlight, there is a whole world of options available, each of which provides the designer with myriad opportunities for using Color in new and exciting ways. I would encourage you to explore the whole range of lamps and qualities of light to see how it effects your perception of Color.
Thank you for reading this series. I hope you found it useful.
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