Atlantic Illumination Entertainment Lighting

(Image: Chromaticity Graphic)

AIEL Instructional


This short instructional teachs the basic, correct, accepted colour theory. Because so many books, Internet websites, and even university-level courses actually have it wrong, people are confused about primary colours. They have been taught old, obsolete 1930s theory.   )-:  What follows is the scientifically accepted, proper colour theory as may be proven by experiment and by logic.

Should this differ from what you have learned,
then you have been taught incorrectly! Please
now learn THIS lesson and then replace
what you currently believe to be true with it.

Note that for this lecture, colour names will have capital
first letters. This is only for distinction during the lesson.



Spectral Colours



Suggested Gel



    White light consists of seven distinct colours: Red, Orange, Yellow, Green, Blue. Indigo, and Violet. These may be seen in nature by viewing a rainbow, and in science by viewing the array of colours appearing when a sliver of white light is shone through a prism. This range of colour is called the "Spectrum". These seven colours may be remembered by the name: ROY G BIV. All colours other than Red, Green and Blue are combinations of these seven basic colours, as interpreted by the human brain. (See "Primaries", farther on.)

    Realise that something looks the colour it is because it reflects or transmits the colour we see and essentially absorbs or blocks all other colours. A Red cloth looks Red because it reflects Red and absorbs the rest. A Red piece of clear glass or plastic passes Red light through it because it transmits only Red and absorbs (or reflects out the back) all other colours.



    Of the seven Spectrum Colours, the human eye has receptors for only three: Red, Green, and Blue. The brain interprets other colours by combinations of stimulations to each of these three colour receptors.

    These three are called the "Primary Colours", or "Additive Primaries". They can be represented by Red, Green, and Blue coloured lights. The following chart shows how the Primary Colours combine to form the Secondary, or "Subtractive" Primaries.


Red    +  Green  =  Yellow

Green  +  Blue   =  Cyan

Blue   +  Red    =  Magenta

    The Primary Colours must be combined in the correct amounts so as to form the Secondaries. Additional colours are formed by varying the quantities. For example, Purple may be formed by using considerably more Blue light than Red. Conversely, using more Red than Blue will form Pink. This may be seen in the chromaticity graphic at the start of this article as the eye moves from the fully blue point along an imaginary line toward fully red.

    If you experiment yourself, be sure to use incandescent or quartz lighting sources of 3200K for the best results. Colours will be created by using standard stage lighting filters (gel). You will notice that as you add more and more coloured light, that near-White light will eventually result if the amounts of each colour are in correct balance. It will not likely be perfectly white because the filters would have to be very pure. (Your stage lighting filters are not pure, and need not be for most purposes. Because of their impurity, 3200K sources are recommended so as to come closest to theoretical results.)



    The Secondaries may be re-combined to get the Primary Colours. These Secondaries are best represented by Yellow, Cyan, and Magenta coloured inks. Painters, dyers, and printers call these Secondary Colours the "Primary Pigments" or "Primary Inks". In lighting, the same results may be had by combining coloured gel, one in front of the other, as seen in the following chart.


Yellow   +  Magenta  =  Red
 (R+G)       (R+B)

 Cyan    +  Yellow   =  Green
 (G+B)       (R+G)

Magenta  +   Cyan    =  Blue
 (R+B)       (G+B)

    Notice that the resulting colours are those that are common to each of the Secondary Colours that are being combined. Using a pigment example, Yellow ink is made of Red & Green, while Magenta ink is Red & Blue. The common colour of Red is the result when the two Secondary Colours of Yellow and Magenta are combined because they BOTH reflect Red while each absorbs the other's remaining colour. This absorbtion happens because one of the colours does not reflect Blue and the other does not reflect Green.

    To translate that example to stage lighting: Place a Magenta gel into a single theatre light and put a Yellow one in front of that; the colour shining out will be Red. This is because the Yellow filter blocks transmittance of the Blue component of the Magenta, while the Magenta filter blocks the Green transmittance of the Yellow. Since both filters can transmit Red, that is what we see. Once again, other colours may be formed by varying the quantity of each individual colour by selecting a more, or a less, saturated Secondary Colour to use when doing the combining. ("Saturated" colours are those that are deeper, as opposed to "pastel" ones, which are lighter in colour.)

    Experiment yourself to find that as you add more than two Secondary Colours of gel, the result will eventually approach, and then become, Black. That is, no light will be transmitted. (Again, because of the impurity of plastic colour media, 3200K light sources will produce results closest to theory.)

    People have a tough time understanding Secondary Colours. Many believe that by combining Blue and Yellow paints they will get Green. However this is not so. Truly Blue paint contains only one colour: Blue. So Red and Green are absorbed while Blue is reflected. Regarding Yellow, Red and Green are reflected while Blue is absorbed.

    Should these two colours be combined (Blue and Yellow), Black will result because the Blue content will absorb Red and Green (Yellow) while the Yellow content will absorb Blue. So all colours get absorbed, thus resulting in Black. (In actuality, a muddy brown or grey will result because the paints are unlikely to be absolutely pure in colour. If they are very impure, other colours may even result.) In the case where combining apparently Blue and Yellow paints does produce Green, then the Blue paint is actually some shade of Cyan and not truly Blue.

    For a good discussion of primary pigments, see:
-The True Primary Colours



    Atlantic Illumination is a Lee Filters dealer and has been since 1975.
This British company has the widest selection of gel colours.
It also offers photographic filters, along with reflection
and other specialty media.

    Below are the suggested Lee numbers and names needed to
experiment with the colours discussed in the preceding lesson.

    You may order them from us as full-size separate sheets (~ 510mm X 600mm).
Large rolls are also available. E-Mail AIEL, or see the AIEL Market.

    In addition, Lee Filters offers a selection of colour packages for experimentation:
Lee Filters Lighting Packs

Once again, if you have been taught any other method,
it is wrong, Wrong, WRONG!. If by chance you see a
person combining Blue and Yellow inks to get a result
of Green, then that Blue is actually a shade of Cyan.

By definition, Blue absorbs Green (and Red).

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