Enlarger Illumination -Dichroic Light Source

These enlarger heads are of the diffused type but have colour filters built into the head usually with cyan, magenta, and yellow. As minor fluctuations in voltage can alter the colour temperature of the lamp in the housing, they also have a stabilizing transformer in line to keep the voltage stable.
This image shows the removal of the mixing head where the light is mixed before it is channeled down through the lens. Also visible are the three filter setting which are measured in CC. I.e. Cyan 60 CC or Magenta 20 CC.
With the head removed the filters are exposed. Each of these are linked to a control on the front or side of the enlarger. As any of  these filters are brought into the light path the rays of light is mixed through the diffusion into a constant quality before it travels down through the head and the negative. While the head is designed for colour work, the filters can be used for Multi contrast B&W printing, it should be remembered that they will produce less contrasty prints than a condenser enlarger.
Here we can see a close up of the three filters which can be moved up or down in the path of the light entering the mixing head to achieve small graduations of change and give the desired colour for printing a particular photograph.