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Let there be colour
Before we look at any type of moving light we need to look at the old school methods for animating light. In the early days of lighting, the only way change the colour of light on the stage was to use one lantern for each colour required. In the case of a followspot, where an operator can manually change colours, it was impractical to keep sliding filters in and out so some bright spark came up with the hand operated semaphore change
A semaphore changer typically has five or more colour frames, each pivoted in one corner, that can be moved in and out of the beam. Each colour is operated by a lever which enables the user to change colour while using the spot. It was only a matter of time before someone realised that a motor could be used to automate colour changing.
The first colour changers that could allow lighting designers to have remote control over colour where probably motorised semaphore changers. These work in exactly the same way as the manual equivalent except the flags are motorised and controlled remotely by the lighting operator. I am not sure when the colour wheel came into existence but I suspect that the ability to control the absolute position of the wheel came later. If you don’t know what a colour wheel is, it is in essence , a wheel made of more than one colour that rotates in front of a lantern changing the colour of the light. Typically the wheel is a metal frame with large holes cut out of it (to allow the light to pass through) where coloured filter is fitted.
The last type of colour changer is the scroller. In principle this works just like the film in a slide projector. A ‘film’ of colour filter called a string or scroll is made up of all the colours a designer needs for a show, including a clear ‘open white’ which is required as there is no option for removing all the filter from in front of the lantern with a scroller. The string must be precisely cut and joined with high temperature tape to prevent jamming or confusing the scroller as the length of each colour filter on the string is not normally measured. The scroller is controlled either by an analogue voltage ranging from zero to ten volts or (more commonly) by a digital signal that allows the lighting operator to control everything from the lighting desk using one or two cables. A minimum signal (0 volts or 0%) represents one end of the scroll and maximum signal (10 volts or 100%) represents the other end. Values between 0% and 100% cause the scroller to scroll on to proportional point on the scroll.
Unfortunately scrollers are not always all that reliable. If the string is not fitted correctly or is cut wrong the scroller could jam, break or just be unpredictable. Many scrollers use optical sensors to locate the end of the string before the tape holding the string to the spindle is ripped off by the motors. In principle this is a good idea, however, dust and fluff can easily stop these sensors working as can the end marks coming off the string.
Now we have the ability to change colour, lets look at moving the light... [ Click Here for Part 2 ]