Module 30 | Updated: 01/27/2008 |
LightingInstruments
"Quartz" Lamps |
HMI Lights
First, compared to standard incandescent lights they deliver five times the light output per watt. This means that they generate less heat, which is an important consideration when shooting inside in a confined space. (Incidentally, HMI stands for Hydrargyrum Medium Arc-length Iodide.) The light on the left side of this picture is a HMI light; the one on the right a standard quartz light. Despite the difference in size, both put out the same amount of light. The color temperature of HMI lights is the same as average sunlight -- 5,600K. This makes them an ideal fill light for on-location work where the sun is the key. The standard quartz (incandescent) light
must use a blue filter to bring it up to the color temperature of
sunlight. Note the blue filter below the quartz light on the right
in the photo above. This significantly reduces the light output when
this light is used
outside. The main disadvantage of the HMI light is the bulky, high-voltage power supply that's needed. The power supply for the HMI light at the bottom left of the photo above.)
The Fresnel lens with its circular glass rings is at the left of the picture (more on that in a second) and the HMI bulb is at the right of the picture. Now that we've covered the lamps used in lighting instruments, we can turn to the lighting instruments that house these lamps. LED Lights In recent years LED (Light-emitting diode) lamps have
started being used in TV studios. A basic studio light, replacing the Fresnel
(to be discussed below) is shown here. LED lights have at least eight important advantages over other types of lighting
elements.1. They produce more light per watt than do incandescent bulbs, not only reducing power costs, but making them useful on locations and in battery powered devices, such as camcorder lights 2. They can be designed to emit light of an intended color without the use of color filters. 3. Unlike incandescent and fluorescent sources that often require an external reflector to collect and direct light, they can be designed to some degree to focus and direct light. 4. When dimming is required, LEDs do not change color as voltage is reduced. 5. Being solid state, they are difficult to damage. Fluorescent and incandescent bulbs are easily broken if dropped. 6. They have a long life -- 35,000 to 50,000 hours. This is longer than fluorescent tubes and far longer incandescent bulbs. 7. Unlike some types of lights, they light up and stabilize almost instantly. 8. They do not generate the amount of heat that many other lighting instruments do, reducing studio cooling costs. Although these are important advantages, especially in this era
of a need to reduce energy consumption, LED lamps have some disadvantages
-- all of which can be controlled or accommodated.1. They are currently more expensive than more conventional lighting technologies -- both in initial cost and light output. This may change, however, as production techniques are refined. The initial cost can be made up over time in reduced operating costs. 2. Performance and life depends on the temperature of the operating environment. High surrounding temperatures or heat build-up (if this is allowed) will reduce both. 3. They require stable voltages and current, which can involve regulated power supplies. 4. The color spectrum typically has two spectrum spikes that can cause some colors to be rendered differently than the way the eye seems them. However, this problem is not as great as with common fluorescent lamps. With the emphasis on reducing energy consumption,
we will probably see LEDs replace many of the familiar studio lights,
starting with....Fresnels
For decades the most widely used has been the Fresnel (pronounced fra-nell) . The HMI light pictured above is mounted in a housing with a Fresnel lens (see below). Although these lights used to be so bulky and heavy that they were confined to studios, recent versions are small enough to be packed away in lighting kits and used on location. The Fresnel lens, invented by French physicist Augustin-Jean Fresnel, consists of concentric circles that both concentrate and slightly diffuse the light. Note the photo on the left below. The coherence (quality) of the resulting light represents an ideal blend between hard and soft. In the studio these lights are typically hung from a grid in the ceiling.
A C-clamp or pipe clamp (on the right, above) is used to attach the light to the studio's ceiling grid. Because of the safety hazard
The distance between the internal lamp and the Fresnel lens can be adjusted with this type of light to either spread out (flood), or concentrate (spot or pin) the light's beam. This adjustment provides a convenient control over the intensity of the light, as well as the coverage area.
Scoops
Because there is no lens, the light is not projected any significant distance. As we will see, scoops are commonly used in the studio for fill light. Note that this scoop shown here has a square filter frame attached to the front. Colored gels, diffusers, and scrims can be slid into this frame to change the light in various ways. Ellipsoidal Spots |
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In some cases, a background pattern (see samples on the left) may be all you need in a medium shot or close-up to suggest a complete setting. For example, a colored stained glass pattern behind a person would suggest that the person is in a church.
Abstract patterns, or patterns suggesting the theme of a program, can also be used to break up what might otherwise be a blank background.
These can either be in the form of a cookie inside the light as indicated in the drawing above, or a large pattern mounted on a stand. When a coherent light source such as an ellipsoidal spot is directed at the pattern, a shadow of the pattern is projected on the background.
These large patterns are referred to as gobos, a term which stands for "go between."
Backgrounds, sets, and settings are discussed in 
this section.
Although Fresnels, scoops, and ellipsoidal spots are the most used types of studio lights, there are also several other types of lighting instruments. Some of these are covered here.
Camera Lights
In ENG (electronic newsgathering) where quality is often secondary to getting a story, camera-mounted, tungsten-halogen or HMI lights (often called sun-guns) are sometimes used as a sole source of illumination.
These lights can be mounted on the top of the camera as shown here or held 
by an assistant.
Camera lights are typically powered by batteries -- generally, the same 12-volt batteries that power the camcorder.
When used as the only source of light they provide the same (questionable) quality as the familiar single-flash-on-the-camera does in still photography.
As a result of the straight-on angle involved, picture detail and depth are sacrificed.
Plus, because of the relationship between distance and light intensity, the detail and color of foreground objects often becomes washed out, and objects in the distance typically go completely dark. (Recall the problem with tonal mergers.)
For these reasons, a camera light works best if important subject matter is all at about the same distance from the camera.
These lights are often used outside in combination with a color-correcting blue dichroic filter to reduce harsh shadows created by direct sunlight.
Attachments to Lighting Instruments
Barn doors
From lighting instruments themselves we now turn to 
attachments that are used with these lights.
Adjustable black metal flaps called barn doors can be attached to some lights to mask off unwanted light and to keep it from spilling into areas where it's not needed.
While barn doors provide a soft cutoff (edge) to the perimeters of the light, flags provide a sharper, more defined cutoff point.
Flags
Flags consist of any type of opaque material that can block and sharply define the edges of the light source. They are often created and shaped, as needed, from double or triple layers of aluminum foil.
Flags are generally either clipped to stands or attached to the outer edges of barn doors. The further away they are from the light source, the more sharply defined the light cutoff will be.
Filter Frames
Filter frames are typically a part of the barn door 
attachment that slides over the front of lighting instruments. They can hold:
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one or more scrims to reduce light intensity
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one or more diffusers to soften the light, or
- a colored gel to alter the color of the light
Each of these simply slides into the filter frame, which attaches to the front of the lighting instrument.
Now that we know the basics of lamps and lighting instruments, we're ready to put them into use. In the next Module we'll start with the most important light, the key light.
