1920s additive color camera exposing three separate film stocks in RGB simultaneously — analog trichromatic system. Rare, but available for experimental work demanding period authenticity.
The Kromskop belongs to that category of camera exotica that today only interests experimental filmmakers and nostalgics — but anyone who engages with it learns a lot about the roots of color cinematography. The system works on the principle of additive color mixing: three separate film strips are exposed synchronously, each behind a red, green, and blue filter. During projection, these three monochrome images are superimposed again to create color.
In practice, it was always a disaster. The mechanical synchronization of the three film chambers required extremely precise engineering work — even the slightest deviations led to color fringing and flickering. The light loss through the filters was considerable, which is why extremely bright illumination was necessary. It might have worked for outdoor shoots in sunlight; interior shots became torture. In addition, one needed not only three cameras or three chambers but also three projectors that had to run in absolute synchronization — an economic nightmare for film studios.
However, experimental works showed interesting qualities: additive color mixing creates a luminosity and saturation that subtractive processes (like later Technicolor) did not achieve. Colors appear to be emitted rather than printed. For artistic purposes, documentaries, or special effects, it is occasionally still worthwhile to engage with it — not least because the surviving originals are extremely valuable as digital resources today and offer new reconstruction possibilities.
Anyone working with Kromskop material today does so almost exclusively in digital restoration and recombination of historical films. Handling it on set is historical, but the conversion into modern color material — the summation of the three channels into RGB digital — opens up entirely new workflows. Some DoPs also consciously experiment with hybrid setups to achieve that classic additive look without taking on the technical hell.