Colour Theory

written 14 April 2000 being revised May 2006
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1   Overview        

Features of this project are: The curriculum objectives:

This project fits the Visual Arts Objective - Developing Practical Knowledge in the Visual Arts. This is effectively a Level 3-5 activity. Colour is typically the last Visual Arts element to be studied, after Line, Form, Sensation... etc.

Technology - one would expect that this project is pertinent to the Technology Curriculum. It deals with the basic problem of presenting colour using various processes and mediums. The curriculum is rather broad but this exercise would seem to fall into Level 3 and 4 of Technical Knowledge and Understanding. The Level 3 component is to do with the way colour is transferred from one technology to another. And what can happen to it on the way. The Level 4 component explores the different technologies, paint, print and computer screen, and how different colour theories need to be used in different technologies. At the same time, the ways that the computer components are connected can also be studied. For instance why scanners and printers have big connection plugs. Also the different formats for storing images.

Mathematics - Colour has not figured in the Math's curriculum because up till now there has been no easy way to empirically measure it. Plotting graphs of the colour mixing and their computer RGB values fits into Level 3 Statistics. The 3-D unit model of colour is the key example of its kind in the real world.

Health and P.E. - This curriculum focuses on overt activity and fails to mention aspects of perception in relation to Physical Education, such as how eyes and ears work, how to protect them, kinds of defects they may have or develop. The effects of tiredness or illness on perception is also omitted. Since pubertal change is covered in level 4, this material should probably be covered in Level 2 or 3.

Overall the two major factors determining when this project is done is the Mathematics graph component and the availability of a scanner for class use, not to mention the cost of colour printing. This project could be done anywhere between Y4-Y8.

2   Exercise 1 - Web Search and Colour Perception        

The first exercise involves sourcing information on colour theory and then doing some practical exercises on the web which compare the students own experience of colour with the theory that has been read.

The theory material does not need to be searched on the web. It can be printed and provided as class material, sourced in the school library, or available in text books.

In the exercises on the Web, the student is asked to note how the theory relates to his observations. Some people can see colour very differently due to some form of colour blindness, while others perceive colour slightly differently due to genetic influences. Therefore the results of the exercise will show some variation. In fact the results themselves will form an interesting information resource about colour perception. It can later be a subject of statistical hypothesis and testing and be a demographic resource.

So there are no "right" answers to this exercise. The comments that the students provide will indicate their understanding of colour theory and the exercise.

The exercise is a simple experiment. It is an instrument on which settings are manipulated and observations made using a simple quantitative measure. However when we perform an experiment we assume that everyone makes the same observations. This is a false assumption, as this experiment will indicate, and is an important lesson to learn regarding the theory of experiments to verify hypotheses.

The second issue with the experiment is the quantitative measure - although extremely simple it is still open to different personal interpretations. It is not easy to test the difference in this measure between different students. But the scale chosen, (little or none, slight, strong) is as simple as can be usefully used. The teacher will need to play with the experiment beforehand, to get some feel for what these three measures mean so as to be able to guide students in their answers.

These are important issues to note with respect to the exercise as an experiment in Physics.

Here is the webpage for the color comparison exercise to be done after the web search.

Finally the relationship between the students observations and their expectations derived from reading about colour theory should be noted. The limitations of Colour theory to predict a perceived colour come into question.

3   Exercise 2 - Colour Mixing        

For this exercise, paper paints and brushes are required. For ease of use, quick drying and ease of washing up acrylic medium should be used. However it should be noted that acrylic paint changes colour as it dries and the scanning in Exercise 3 should not be done until this process has completed. Students are each given 2 pigments and white with which to paint a page of colours. Since these pages are going to be used for a number of tests, and will stand as a permanent record, good quality pigments and paper or better still canvas should used. This should probably be provided by the teacher so that a uniform quality result is achieved. A sample page can be displayed to give students some idea of what is expected in the final result. A sample page is included in the webpage instructions for this exercise. The pigments should be artist quality if possible, and at the end of the year the final book of pages could be given to an achieving Art student, as a book such as this is an everyday resource for an Artist. The colours should be assigned to the students to ensure a balanced and comprehensive set of colour combinations is tested.
The Reds Oranges and Yellows

Alizarin Crimson
Light Red Oxide
Cadmium Orange
Yellow Ochre
Raw Sienna
Burnt Sienna
Raw Umber
Burnt Umber
Cadmium Yellow Medium
Cadmium Red Deep

The Blues Greens and Purples

Prussian Blue
Cobalt Blue
Cerulean Blue
French Ultramarine
Phthalo Blue
Dioxazine Purple
Permanent Green Deep

This list provides 40 colour combinations.

The scale of mixing ratios is chosen to make mixing easy.
Starting with 1:0 a pure colour from the Blue set, and 0:1 a pure colour from the red set. Mix equal parts of each colour to get the 1:1 ratio mix. Then mix equal parts of the 1:1 and pure colours to get the 1:3 and 3:1 ratios. Work out to the 31:1 and 1:31 ratios. For the white tint rows use the same mixing ratios 1:1, 1:3 and 1:7.

Each student will apply the paint differently - but encourage a medium coverage with reasonably even and well mixed application. This will help ensure good quality results in the following exercises.

As each page is completed, pin it up to dry so that other students can see results, and compare to their own work. Some students may need 2 or 3 attempts to mix and apply the colours to their satisfaction.

4   Exercise 3 - Scan and determine RGB values        

The painted pages are scanned and stored. A photoimage editor is used to observe the RGB colour value of each colour swatch. This data is then plotted on a dot graph against the colour mixing ratio. This is not a simple exercise on two counts. Firstly the RGB is a 3 dimensional value and each component needs to be plotted separately. Secondly the colour mix is a ratio. A unit scale should be used from 0 to 1. 0 represents a ratio of 1:0 while 1 represents a ration of 0:1. The midway point (.5) represents a ratio of 1:1 and the ratio 1:3 is plotted on the .75 line.

The point of this exercise is to see if the colour components form a linear graph. Some may, some may not. The students can suggest reasons based on what they have already learned about colour for why some graphs are not linear. In particular we perceive a wide range of green that is not reproduced well in computer or printed media. So we would expect the green graph to "cutout" at its ends.

5   Exercise 4 - Print and determine degradation        

In this exercise the colour swatches stored on the computer are printed out and rescanned. The new scans are then observed using the same photoimage editor and the new RGB values noted and compared against the initial ones. The degree of degradation caused by the printing process is measured. This data gives students some insight into how to enhance computer images to restore the effects of colour degradation.

6   Exercise 5 Photography and enhancement        

The initial colour painted pages are photographed using a polaroid camera and the prints are scanned and their RGB values are assessed. This information is added to the previous two sets of direct scans and printed scans and comparisons made as to how the photographic process distorts colour. Students will already know from the web links that photographic processes can incorporate quite strong colour biases.

Again students learn how to enhance colour in images to restore them as well as possible to their original colours depending on the processes that the colours have been subjected too. For instance the Polaroid process is relatively good at capturing blues but poor at capturing yellows.

Students may also wish to measure the degradation caused by time or ultraviolet light on the painted, printed and photoed swatches.

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