Light sources

Tungsten

Vacuum tungsten lamps are widely used forms of artificial lighting in photography, film and television. They have a color temperature between 3200K and 3400K. Despite the extensive use of flash in a commercial studio, prior to any flash exposure the way a subject is lit is determined by the tungsten modelling lamps built into the flash heads. Flash gives a much shorter exposure time and a comparable quality of light to tungsten. It should be taken into account when learning the use of tungsten light that all film and television lighting is tungsten based. Generally they all fall into two major categories, floodlight and spotlight.

Floodlight A floodlight produces a spread of light across a subject. The light from the globe bounces off the reflector in which it sits and travels forward as a broad light source. This diffuse light gives ‘soft’ edges to the shadows and some shadow detail. The quality of the light is similar to that of sunlight through light cloud.

Spotlight A spotlight can concentrate light at a certain point. The light is directed forward by a hemispherical reflector and focused to a point by a focusing (Fresnel) lens. The shadows will have ‘hard’ edges with no detail. The quality of the light is similar to direct sunlight. Spotlights can be flooded to give a more diffuse quality. This change from spot to flood is achieved by moving the lamp and the reflector inside the lamp housing away from (spot) or closer to (flood) the lens at the front of the light. On ‘full spot’ shadows are harsh with no detail, on ‘full flood’ shadows are softer with some detail. Most spotlights come with barn doors and nets. Barn doors are metal flaps attached to the front of the light and control the shape and amount of light. Nets are pieces of wire gauze of varying densities that reduce the output of the light by diffusing the light at its source without greatly affecting the shadows. They are manufactured in half and one and two stop increments.

Rodrick Bond

Flash is a generic term referring to an artificial light source of high intensity and short duration. It has a color temperature of 5800K and is balanced to daylight. Unlike tungsten it is not a continuous source of light. Between flashes it has to recycle (recharge) to maximum output before it can be used. Large tungsten lights have an output 100 times greater than the average household light. With a film rated at 100 ISO this will give exposures of around 1/60 second at f4. A modest studio flash with an output of 5000 joules (measurement of output) at the same distance from the subject as the tungsten light will give exposures of around 1/500 second at f11. This is six stops faster or a ratio of 64:1. Its advantage when photographing anything that moves is obvious.

The advantage of modern flash is its lightweight construction and versatility. Most studio flash systems consist of a power pack, flash heads and attachments. The power pack is usually a separate unit where light output is stored until the instant of exposure. After exposure the power pack recharges ready for the next exposure. Recycling times vary from seconds to fractions of seconds. The faster the recharge to full power the more expensive the unit. The flash heads are the actual light source. The basis of their design is to produce light similar to that produced by floodlights and spotlights. The way in which this is achieved ranges from varying sizes of reflector bowls similar in design to a floodlight to a focusing spotlight equivalent to its tungsten counterpart. Flash, being a non-continuous light source, is generally confined to ‘still’ photography whereas tungsten lighting is used almost exclusively in ‘moving’ photography (film, video and TV). However, the lessons learned with one light source apply equally to any other.

Mick Downes

Activity 1

Using various resource material compile a collection of studio photographs using tungsten or flash as a light source. Divide into the two categories. Consider why a particular light source was used, its advantages and differences.

Swimming pool, soft box, fish fryer and others are names for variations of a floodlight. In some the light source is placed inside and to the rear of a collapsible tent with direct light transmitted through a diffuse front surface. In others the light is reflected off a white/silver surface before it is transmitted through a diffuse front surface. These sources create a very soft diffuse light with minimum shadows. Soft diffuse light is also created when flash is used in conjunction with a collapsible umbrella. With umbrellas having a white/silver inside surface, light can be directed into the umbrella and reflected back onto the subject creating a quality of light similar to a soft box. With umbrellas having a transparent diffuse surface light can be directed through the umbrella creating a quality of light less diffuse than the reflected light from the white/silver umbrella.

James Newman

Spotlight

The use of an open flash (direct light to subject without diffusion or reflection) will give the same effect as a spotlight. Some brands have focusing capabilities closely imitating Fresnel spotlights. The light will be hard with no shadow detail. Barn doors, nets and filtration of the light source are approached in exactly the same way as a tungsten source.