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
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 was manufactured until
the end of Omega enlarger production.
The D5500 Dichroic
lamphouse represented 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.