The introduction of the Chromega colorheads in 1959 ushered in a new era of color photography.  Previously, color printing had been a laborious and time consuming task, using either the additive system - three separate exposures through red, blue and green filters usually mounted under the lens - or the subtractive system which required adding and removing yellow, magenta, and cyan filters in a filter drawer in almost complete darkness. 

With a colorhead, the user had only to adjust a dial to change filtration values, thus saving considerable time and increasing productivity tremendously.  In addition, since they were diffusion lamphouses, they added a significant level of dust and scratch suppression, further increasing productivity and reducing costs.

The original Chromega heads used the same type of acetate filters as were previously used in subtractive printing, but mounted in a wheel-like arrangement so the filtration could be adjusted by dials.  Since diffusion lamphouses are less efficient than condensers in terms of light output, two 100w incandescent lamps were used.  Even so, rather lengthy printing times were required, especially for small format negatives.

The second generation of Chromega heads improved on the design by utilizing recently developed tungsten-halogen lamps which were more efficient than incandescent both in terms of light output and the fact that the lamps did not blacken with age.  The Super Chromega heads also used interchangeable "integrating spheres" so that light output was significantly increased for smaller formats.  However, the weakness in both designs was still the acetate filters which faded in use and required regular replacement.

The next generation of Chromega heads incorporated more new technology - quartz-halogen lamps with highly efficient built-in reflectors, and one-piece, fade-free dichroic filters.  The dichroic filters were adjusted simply by moving the filter further forward or back in the light path.  "Mixing chambers" thoroughly mixed the filtered light with the non-filtered to provide consistent illumination.  It also meant that the entire housing could be altered to a smaller box-like design.  This type of Chromega lamphouse is the one still in production today.

The D5500 Dichroic lamphouse represents a fourth generation - the application of electronic control to the lamphouse. Servo motors in the lamphouse adjusted the filters while the user input those changes from a counter-level control panel. Sensors monitoring the light output adjusted the filters automatically if anything caused the filtration to vary from what the user had set. This "Closed Loop" system provides repeatability that cannot be matched by mechanical systems. The Controller also provided a port to allow the unit to be connected to a computer, and with the optional Translator/Controller, the unit could be connected to a VCNA.