kino flo and colour science
Everything you wanted to know about colour temperature and LEDs (but were afraid to ask...) Kino Flo’s research on the colour science behind LEDs and camera interaction is a complicated affair Words: Paul Middleton Over the past few years, Frieder Hochheim has been presenting the results of research his company, Kino Flo, has been doing into the colour science behind how LED lights react with different types of video cameras. It was something Bernie Davis first reported on in Set & Light126. Cirro Lite (who distribute Kino Flo fixtures in Europe) hosted a Zoom meeting in February to help members try and get to grips with why LEDs and digital video cameras don’t always mix as well as you might like (you can watch the video on YouTube). Before watching it, I felt it would help some people, or more probably, a lot of people, understand what Frieder talks about by going through a brief history of colour theory, and give some more background of the terms and concepts he uses, as well as some history of colour on film and TV to see why Colour Temperature is so important. Sir Isaac Newton first investigated the splitting of white light into its constituent colours via a glass prism in 1666 but until the 1830s, no one had really thought about reproducing a scene by anything other than painting it. There was great debate about whether light was made up of particles or waves of light, and whether the colour of an object was a result of the light it emitted when illuminated by a beam or by the way the wavelengths were reflected, or absorbed, by the object. We now know the latter is the reality. Newton eventually proved that the rainbow effect of a prism was not caused by imperfections in the glass, but by the light waves being refracted in different amounts as it passed through. Henry Fox-Talbot first produced permanent still pictures around the mid 1830s and Louis Daguerre had a different system around the same time but these were monochrome and because of their low sensitivity needed to be used somewhere there was a good amount of light (i.e daylight). In 1887, the wavelengths of the different colours of light were first measured by the Michelson interferometer and around 1888, William Friese-Greene was credited as the inventor of ‘Kinematography’. He is probably lesser known for also patenting a two-colour movie process in 1905 that 18
Set & Light | Spring 2021
went on to become the basis of the original Technicolor film system in 1916. It was not until ten years later though that John Logie-Baird produced his first monochrome TV pictures and also amazingly went on to demonstrate the first live colour TV pictures using a mechanical two-colour system just two years later. The various properties of light are due to the behaviour of extremely small particles called photons that are invisible to the naked eye. We cannot see light. We can only see it when it hits something and the colour of that object is revealed. In 1905, Einstein proved that photons have energy (E) equal to (h), Planck’s constant x oscillation frequency. The brightness of light is decided by the quantity of photons. The energy is packed in and each is of a certain wavelength and has a specific fixed amount of energy. The energy of light is thus not the amplitude of the wave, as is the case in acoustical waves. More light means more photons. This discovery led to the formulation of quantum mechanics. Black and white movie film in the late 1920s had a reasonable grey scale response, but the ASA value was very low so a lot of light was still needed to expose it properly. Shooting outdoors was the norm as lighting levels needed when shooting indoors without any daylight were high. The same restrictions also applied to all early TV scanning systems which were also very insensitive. Early colour movies used prisms to separate red and green onto alternate frames of a monochrome film running at twice the normal speed. The alternate frames were then printed on separate chemically-tinted reels and physically stuck together to give the full-colour effect. As the sensitivity of film increased, it became practical around 1930 to shoot in studios using the Tungsten filament lamp that was in widespread use in photographic studios. As
