3 Lighting Sources and Equipment

© Tim Meyer

Creating Light

We need light to make photographs. Like the painters of the Renaissance, we create the lighting environment in a way that allows us to envision and capture the portrait. To do this, we need to understand how to control light. We will deal with this topic in this chapter, discussing light and lighting equipment, and in the next chapter, where we will discuss the modification of lighting.

Discussing light as energy is the most accurate way to approach this subject. Light, regardless of type, is part of the electromagnetic spectrum (EMS). When there is a release of energy, there is the potential that part of it will be released as visible light. All light that is used in photography involves an energy release, whether it is the sun, continuous light, or electronic flash.

We will begin by introducing incandescent and ambient light, including sunlight, and then concentrate more on electronic flash since it is so prominent in photographic portraiture. We take this approach to lighting because all light, regardless of how it is generated, acts the same. Therefore, the controls we use with electronic flash are the same as those used for sunlight or incandescent light.

Continuous Light

While not heavily used in contemporary portraiture, some photographers do rely on continuous lighting equipment. Most common are incandescent lights, but soon we may see more solid-state light-emitting diode (LED) systems. The advantage of continuous lighting is that there is no difference between the light seen before the shutter is activated and the light present for capture.

Incandescent light is the easiest type to understand from a generation standpoint. It is created from heat, and the heat is the energy source that releases the light. The sun, fire, candles, and light bulbs create light in this manner. To understand how this works, look at a common light bulb. The bulb is constructed of a glass envelope filled with an inert gas and a tungsten filament, which is a doubly wound fine wire. This construction has a very small cross section with a larger surface area. When electricity passes through the filament, it heats up and glows. As the filament gets hotter, its color changes from a warm red to a bright yellow.

Incandescent lights are used both as lighting for portraits and as integrated modeling lights for electronic flash. For primary lights, there are two types of bulbs. Photofloods, an older technology, are traditional in design and have a limited color life consistency. Quartz halogen bulbs, or tungsten lights, have extended color constancy because of their high heat. Regardless of the type, incandescent lights use a great deal of electricity and generate a great deal of heat. In addition, the “hot lights” can make the subject of a portrait uncomfortable. Newer LED systems have the advantage of reducing both power usage and heat.

Ambient Light

Ambient refers to light that is not part of a lighting pattern created by equipment. This can be light from an open window, light in nature, or other sources that provide light to a set. Ambient light is most obvious in environmental portraits, but it is also a major concern in outdoor photography. When present, it does not necessarily become the main lighting or key light, and it may or may not be involved in the image capture.

The sun is the most available form of ambient light and it is often used in portraiture. The sun provides the majority of the energy reaching the Earth. Depending on the cloud cover, the light can vary from specular to exceptionally diffuse.

As far as photography is concerned, the distance from the sun to Earth is constant. This leads to the “Sunny Day Rule.” During midday (between 10 a.m. and 2 p.m.) with clear sky conditions, the proper exposure is f/16 at a shutter speed of the reciprocal of the ISO. This exposure method is accurate and is further developed in the Basic Daylight Exposure method (described in chapter 5). If direct sunlight is used as the key light for a portrait, that is lighting the face of the subject, then this method gives the base exposure.

When making a portrait in ambient light situations, you must consider whether the ambient light will be the main light source or whether other sources will be required.

Window Light

There are several considerations when using window light. First is the direction the window faces. If the window allows direct sunlight to enter, it will have a different color bias than a window facing away from the sun. Also, if the sky is clear and sunlight shines directly into the area used for the portrait, it can be used either as a specular source to light the subject or to create effects on the background. However, because the sun constantly moves in the sky, it tends to be unreliable as a controlled source to create a particular lighting style. If the light enters the room from an overcast sky or away from the sun, it will have a blue cast and be more diffuse the closer the subject is to the window.

Window light is often used in a found environment. As compared to a studio with window light, it is more difficult to envision modifying the light in found settings with lighting equipment. This situation can be addressed with portable power packs and small, self-contained electronic flash units. However, whether in a studio or in a found environment, window light can serve as the concept setting light if not the key light for the portrait itself.

Monoblock self-contained unit, left, and studio power packs and heads, right (Courtesy of Profoto)

Strobe Light Sources

Unlike incandescent light, electronic flash, or strobe light, results from an atomic particle action that causes the gas enclosed in a flashtube to glow. To make this glow, electricity passes through an inert gas, usually xenon, causing electrons to move out of orbit. As the electronic charge subsides, the electrons return to their original orbits and release stored energy that causes the gas to glow. With the speed of the electronic energy flow, the glow is very short. The energy is released primarily as visible light approximately the color temperature of daylight. A substantial amount of ultraviolet light accompanies the visible light.

The major concerns for strobe equipment design are the strength of the light, the duration of the light, and the flexibility of the unit. Strobes create less heat than incandescents, and heat dissipation from the electronic flash is not a great issue. A more important issue for strobe lighting equipment is holding the charge needed to affect the flash and getting it to the flashtube to create the light. This is handled by the capacitor. The normal way to discuss the power of an electronic flash unit is through the watt-second rating of the capacitor. The higher the watt-second rating, the more light can be produced by the unit. As the light intensity increases, so does the duration of the flash. The power from the capacitor is limited based on the flashtube, so the flashtube must be matched with the power to be released through it.

In terms of the need for flexibility, strobe lights come in two formats: monoblock self-contained units and studio power packs. With monoblocks, the flashtube, capacitor, and controls are all contained in one unit. The unit can be placed anywhere as long as a power supply (usually an electrical outlet) is available. With monoblocks, there are several concerns dealing with the flexibility of power settings once the unit has been positioned. However, just as remote firing has been provided to monoblocks, some higher-end units allow remote control of discharge amounts.

Ring light
(Courtesy of Profoto)

Studio power packs are often called generators because they may use a generator to charge the capacitor quickly. These units include the capacitor, a method to charge the capacitor, and devices to control flash power. With the packs located either on the ground or in other stable locations, weight is not an issue, allowing for larger capacitors and greater light output. As mentioned, there must be a match between the capacitor and the flashtube’s ability to handle the energy sent to the flash head. If excess power is sent to the flash head, it can destroy the flashtube.

It is common for power packs to allow the connection of multiple flash heads with cabling. With all the flash heads attached to a single control unit, synchronization and control are simplified. In addition, the flash units themselves are simpler in design and lighter. However, cables will cross over spaces within the studio.

On location, an extension of the power pack is the portable flash pack. This is a highly efficient rechargeable battery that includes a circuit for connecting a flash head.

Most flash units, whether monoblocks or packs, use modeling lights to allow the photographer to see the approximate lighting effects that will result when the flash units fire. Today, these modeling lights are incandescent bulbs; on higher-end lighting equipment, they can be proportional to the amount of the light that will be created with the flash. A rheostat that controls the output of the modeling light is connected to the power controller so the capacitor can coordinate the approximate output. Problems with accuracy of modeling lights can be attributed to differences between the size of the modeling light bulb and the size of the flashtube and differences between their respective axes. However, depending on the design of the flash unit, these effects can be greatly minimized.

An additional specialized piece of lighting equipment is the ring light. This is a strobe designed to fit around the camera lens and send its light straight at the subject, creating a unique highlight and shadow signature. It is sometimes used as a fill light; since it comes from the same axis as the camera, it avoids the shadows created by typical fill lights. It adds a unique specular highlight to skin and is used extensively in fashion work for this reason.

Activation of the flash unit occurs when the capacitor’s charge releases into the flash tube. There are three basic ways to activate the unit. The oldest method is a PC cord, wiring that connects from the camera to the flash unit or studio pack. The PC cord is mounted through a PC connector integrated into the camera or hot shoe. Another method is an “optical slave” attached to the flash unit that is activated by a bright on-camera flash or the discharge from another unit. The last activation method is an infrared or radio trigger that sends a signal to a receiver on the flash unit. This remote activation can also be used to trip the shutter release, allowing the entire capture process to be completely away from the camera.

Because light generation takes a few microseconds, the flash unit and the camera shutter must be synchronized. In-lens leaf shutters do not have major problems with synchronization, but it can be a problem for shuttering sensors and focal plane shutters.

While an electronic flash may appear to be instantaneous, the light takes a short time to reach its full intensity. To address this temporal concern, many on-camera strobes have the ability to automatically adjust or stop the output when the correct amount of light reaches the film or sensor. A thyristor/quenching tube circuit diverts energy coming from the capacitor when the light energy from the film or the sensor reaches the proper level.

The release of energy from the gas that creates visible light in the flashtube generates a great deal of ultraviolet light, sometimes causing a problem called anomalous reflection. When the light from the flash reflects off certain materials, it can reflect more ultraviolet energy than normal and make the color shift to a bluish cast. This happens most noticeably with color-enhanced synthetic materials and other materials washed in brightness-enhancing detergents. This problem can be easily corrected with the use of an ultraviolet filter coating on the flashtube.

Power Requirements

Power consumption and access are ongoing concerns with lighting equipment. Dependable power sources are a necessity, whether in the studio or on location. Access to power determines which lighting equipment can be used. While wall outlets, generators, or batteries provide power, each piece of equipment creates its own draw and can stress wiring and/or produce an overdraw on the power supply.

In the studio, multiple circuits are required for lighting equipment, digital cameras, and computers. While electronic flash is less of a power draw, modeling lights (commonly quartz halogen bulbs) and generators or charging systems are heavy power consumers. Surge protection also plays an important part in modern studio electrical systems because of the use of microcircuits in most equipment, including electronic flash, cameras, and computers.

© Stacy Pearsall (Courtesy of the artist)

Several safety issues need to be addressed when working with any electrical equipment. With power packs, cables will cross the studio, and with monoblocks, wiring will be present throughout the setup. Also there are heat concerns, particularly with incandescent lighting such as modeling lights in electronic flash. Equipment and lighting situations that use quartz halogen lights need good ventilation with air movement to allow the heat to dissipate. Without care, the dissipation of the heat created can cause fires or other heat-related problems.

When quartz halogen lights are used, whether as direct sources or as modeling lights, care must be taken with the bulbs even when they are cool. In all situations, you should follow safety warnings with each piece of equipment.