Almost any type of light can be used for copy work, provided the intensity of the light is enough to prevent excessively long exposures. Another principle requirement of the light source is to produce a light with a color temperature suitable for the type of film being used.

Tungsten Lamps

Tungsten lamps 3200 K and 3400 K are suitable for normal black-and-white copy work When a reflector type of bulb is used, the need for external reflectors is eliminated. A lens shade should be used with a reflector type of bulb because the built-in reflector does not extend the full length of the bulb, and stray light may reach the lens and cause flare.

Lamps such as 3400 K are not as economical to use as 3200 K lamps because of their short life (4 to 6 hours).

Fluorescent Lights

When fluorescent tubes are used to light an original, they should be arranged to form a square-the sides of which are parallel to the edges of the copyboard. The size of the tubes and their distance from the copyboard are governed by the size of the original to be copied. Because this type of lighting setup is not easy to adjust, it is best used when the size of the originals to be copied does not vary much from one to another. Because of its diffused nature, fluorescent lighting is suitable for copying originals with a textured surface that must be eliminated in the finished print. Regular fluorescent lights should not be used when shooting color film because it is difficult to color correct them accurately. Special fluorescent lamps with a high color-rendering index (CRI) should be used whenever possible. When ordinary fluorescent lamps are used, consult the Photo-Lab-Index to determine what filter should be used as a starting point for the type of film you are using.

Electronic Flash

When used properly, electronic flash units are an excellent light source for copy photography. An electronic flash unit allows for extremely short exposures that can be helpful for shipboard photolabs when the ship is underway. The flash unit is balanced for daylight color film and does not produce the heat associated with tungsten or quartz bulbs.

Unless specifically designed for copy work and attached to the copyboard, electronic flash lamps may be difficult to position for proper illumination of the original. The task can be made easier if you use studio electronic flash units with built-in tungsten modeling lights. With this type of lighting unit, the modeling light can be used to position the lights accurately for even illumination of the original. Even with this, the light may have to be heavily diffused to prevent hot spots. A hot spot is a surface area that receives too much light, causing an unwanted reflection that is noticeable in the final copy product.

Quartz-Iodine Lamps

The quartz-iodine lamps (tungsten-halogen) are of the incandescent variety but bear little resemblance to conventional light bulbs. A quartz lamp is a short tube of quartz glass, housing a coiled filament that runs the length of the tube. In ordinary tungsten lamps, the tungsten evaporates from the filament and settles on the glass and gradually darkens the bulb. In the quartz-iodine lamp, however, iodine vapor combines chemically with the tungsten and causes it to redeposit on the filament. This prevents the tube from becoming tarnished with age. The intensity and color temperature of the tube remain almost constant throughout its life. Although the quartz-iodine lamp is very small, it produces intense light that is particularly suited for copy work. There is a disadvantage-quartz-iodine lamps generate extreme heat that could cause your original to curl. You should never touch a quartz-iodine lamp with your fingers. The oil from your hands can create a concentrated hot spot on the lamp, causing it to bubble and burn out.

LAMP REPLACEMENT. As lamps get older, their color characteristics and light intensity may change. Therefore, when one lamp in a set bums out, the new replacement lamp is usually brighter and has a different color temperature than the remaining lamps. You should replace all the lamps, not just one to avoid the need for adjusting the new lamp to get even illumination. Replacement of all lamps in a set is particularly important when you are copying with color film because the color temperature of the new lamps is higher than the old lamps. The variation in color temperature would be seen as an uneven color quality over the resulting reproduction.

VOLTAGE VARIATIONS. Fluctuations in the voltage or electric current affect the color temperature of copy lights. When the voltage to your copy lights varies, consult an electrician. The electrician can trace the source of fluctuation and recommend the best action to overcome the problem.

Parabolic Reflectors

An important element of the lighting equipment for copy work is the reflectors. Parabolic reflectors should cause the light to be evenly distributed over the surface area of the original and not cause hot spots. Certain types of lights, such as reflector photoflood lamps, have built-in reflectors. By use of the correct reflectors with artificial light sources, exposure times can be shortened.

Daylight

Daylight can be another excellent source of illumination for copying. When the sun is used, you should try to use the sun during the midday hours where a combination of daylight and skylight is present, because of the shifting of color temperature throughout the day. The early morning and evening hours should be avoided when color film is used, because the lack of blue light present. Heavy overcast skys or copying in shadow produces a bluish cast and should be avoided or corrected with a filter.

Filters

The use of filters was fully discussed in chapter 3. Both correction and contrast filters, as well as special filters, are used extensively in copy work

FILMS FOR COPYING

For copying, you can achieve the best results by selecting the correct film for the type of copy work to be done. Copy-type films are designed specifically to compensate for the compression that occurs in tone reproduction and it provides an improved highlight tonal separation. Copy films are available only in 70mm and sheet film formats. Although 35mm film can provide acceptable results, you should use sheet film since it provides higher-quality enlargements and is easier to retouch.

Film characteristics, such as color sensitivity and contrast, are important when you select the film to copy a specific type of original. Film characteristics were discussed in chapter 2.