Ease of operation in total darkness A good quality enlarger is required to produce high-quality color prints. Color enlargers used in Navy imaging facilities are diffusion type of enlargers. Like all image-forming equipment, the lens is an integral part of the enlarging system. The lens used in a color enlarger must be free of chromatic aberration; that is, it must be a  color-corrected  lens. COLOR   TEMPERATURE The color temperature of light used to expose the color  material  must  match  the  spectral  sensitivity  of  the color material. This is true when making the original camera exposure, and it is also true when you are printing  color  materials.  In  color  printing  equipment, color temperature is usually regulated by adding filters to balance the light source and by regulating the voltage source  supplying  the  lamp. Corrective  Filters In color printing, three emulsion layers in the printing material must be correctly exposed from the three color images in the negative. The exposure of these three layers is manipulated by both exposure time and the  color  quality  of  the  exposing  light  reaching  the  paper. The color or quality of light is altered by placing color filters in the light beam of the enlarger. You can use color printing (CP), color compensating (CC), or dichroic filters. CP and dichroic filters are placed between the light source and the negative. Generally, dichroic filters have  replaced  CP  filters.  Dichroic  filters  more accurately control the light, and unlike gelatin filters, do not fade over time. CC filters are placed between the lens  and  the  light-sensitive  paper. The filters that control the exposing light are called the filter pack The basic filter pack differs among each characteristic of color negative film; that is, film size, manufacturer, film type, and film speed. For example, the basic filter pack for 35mm Kodak Vericolor III differs from the basic filter pack of 120 Kodak Vericolor III. The basic filter pack for 35mm Scotchcolor differs from the basic filter pack of 35mm Fuji color. The basic filter pack for Kodacolor Gold differs from Kodak Vericolor III. The basic filter pack for Kodacolor 100 differs  from  the  basic  filter  pack  of  Kodacolor  400. In addition to CP, CC, and dichroic filters, a CP2B or equivalent filter is usually built into the enlarger to absorb  ultraviolet  radiation  emitted  by  the  light  source. Voltage  Regulation Fluctuations  in  line  voltage  are  more  common  than most people realize. Power fluctuations affect both the intensity and color quality of a light source. As little as a  5-volt  variation  in  the  normal  operating  range (l00-125volts) can change the output of a lamp by about 15 percent. This change in voltage results in a change in the color quality of the light source. This variation is about the equivalent of a CC10 filter. To prevent voltage fluctuations, you must connect the  enlarger  to  a  voltage  regulator.  Most  voltage regulators provide a constant voltage between 95 to 120 volts. Two main types of color enlargers are in common use by the Navy. The two color enlargers differ in the way they control the exposing light. They are the subtractive  and  additive  printers. SUBTRACTIVE   PRINTERS The subtractive type of color enlarger uses a dial-in dichroic filtration system. This type of color enlarger has three filtration controls that move yellow, cyan, and magenta filters into the path of the exposing light. Segments of the dichroic filters are moved in and out of the exposing light beam on calibrated cams. This type of filtration system provides accurate and repeatable filter  pack  combinations. Most color enlargers use a tungsten-halogen light source. These light sources produce a great amount of heat. When a tungsten-halogen light source is used, the color printer must have forced-air cooling fans in addition  to  the  heat-absorbing  glass.  An  ultraviolet absorber, such as a Kodak Wratten Filter No. 2B (CP2B), must always be included in the light beam, preferably above the negative. The most common type of subtractive printer used in the Navy is the Chromega D dichroic enlarger. NOTE: Never touch a tungsten-halogen bulb. Handle it only by the edges or reflector cone. Oil from your fingers can heat up and create a hot spot on the light bulb, causing it to burn out. If you touch the bulb, clean it with a soft cloth and isopropyl alcohol. Allow the bulb to  dry  thoroughly  before  energizing. ADDITIVE   PRINTERS The additive type of color enlarger uses the additive or primary colors of light (red, green, and blue) to expose color printing paper. This type of enlarger uses 12-4