After the first three more theoretical and philosophical parts of the article, this part deals with the practical uses of colour in our Light Painting pictures. What possibilities do we have for creating coloured light trails in a picture? How do we illuminate a room in colour?

Probably the most commonly used method in light painting to “colour” light is the use of colour filter films or “gels”. These films are available in many different colours, they are heat resistant and they are relatively inexpensive. We usually buy films from LEE filters – the films are quite expensive compared with others, but they have clean, well-defined colours which means if I buy a new roll of “Tokyo Blue” after 3 years, I can be absolutely certain that the colour will be absolutely identical to the previous roll. This is not the case with many inexpensive films as the colour is not specified so precisely. They may simply be designated as “red” or “blue”.

However, there is a problem when used on current high-power torches. The film emits smoke signals within a very short time. The picture shows the FENIX LR35R with 10000 lumens. After two seconds, the foil looked like the picture. This is not a DIY film from the 1€ shop. This is high-quality headlamp film.

Acrylic colour filters are more heat-resistant than foils. At some point, however, even the acrylic filters will melt. If possible, you should not operate the 10000 lumens at the highest level when using a colour filter.

An alternative to using colour gels between the flashlight and light painting tool is to use light painting tools which are, themselves, already coloured. In this case, you simply need to attach a white flashlight and away you go. The obvious disadvantage of this approach is that, of course, you now have to pack five different coloured tools if you want to paint five different colours. This takes up a lot more space in the backpack than one tool and five small pieces of foil. With this approach, you can however apply different colours to different parts of the tool or stick different colour foils on the outside to create multi-coloured tools. All the tools shown below are very cheap and to be honest, such things tend to end up in the garbage! Just keep your eyes open and, if in doubt, attach it to a flashlight to see whether it will make a good new light painting brush.

In my opinion, the best solution for creating coloured light is to emit the light in the desired colour in the first place, rather than “colouring” it with a filter. Whereas a coloured LED solely emits light at the desired frequency, a filter takes white light and simply blocks all wavelengths except for the desired colour. The result of this is that coloured filters can decrease the intensity of the light, and the strength of the reduction in intensity depends on the colour selected. A bright orange filter will absorb about 20% of the incident light whereas a dark blue may block as much as 80%. Due to this effect, the 3000 lumens become 2400 lumens when passed through an orange filter and only 600 if passed through a blue filter. This causes problems when working with colour gels as, if I want to use both orange and blue in the same image, I need to remember that they will have different intensities and as such I will have to illuminate much longer with the blue filter than with the orange.

The LEDs in the flashlights in the above picture are identical in performance. All of the colours have a luminous flux of approximately 900 lumens and will therefore show up in the finished light painting with equal intensity. Although this is extremely convenient, the disadvantage of this approach is that the number of available colours is limited.

The only problem: most colours are not available as ready-made torches. I assembled most of the torches in the picture myself. In the case of the Convoy S2+, it's quite easy. There are empty housings in many different colours, matching PCBs with the coloured LEDs and matching drivers available.