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Spectrum is the journal of the Colour Society of Australia – and only available to members.
The Spectrum contains information about events and developments within the Society and in the international area, including the text of papers delivered at National and international conferences and divisional meetings. Members are encouraged to submit original information for publication. We invite your comments and letters with relevant and interesting points of view for potential inclusion in future issues of Spectrum. Longer articles may be edited or serialised for publication.
The Spectrum Editor is Glenys Thomson: glenysdesign@smartchat.net.au
A recent article from Spectrum: Autumn/Winter 2008.
Digital Paint Colours - comparing monitor colour to physical colour: a journey between Art and Science!
Rex Hesline, MDIA -
Spectrum 2008
Around the world today many house paint consumers are turning to computer colour to assist them in purchasing paint colour. Paint Manufacturers have long known that while they are in the business of selling paint – customers are generally in the market to buy colour. It does not matter that manufacturers know most consumers must buy paint to protect the exterior or interior of one of their most valuable assets, such as the family home. Until that consumer has the confidence they have chosen the “right” paint colour for the job – no sale will be completed. The difficulty is in finding the “right” colour. Assisting their clients to confidently select colour is a critical part of any successful paint business.
A quick history of improvements in paint colour offerings.
The first Cave dwellers who started decorating their walls with paint around 30,000 years ago used locally available earth pigments and charcoal for colour. This was handy, because the colours were laying about, even though the range of colours was limited. In Roman times the most popular colours of the Red and Blue lakes: namely Madder, Cochineal, Kermes, Purple and Indigo were available. Roman Villas from ancient Pompeii and Herculaneum have survived where coloured and decorative paints created 2000 years ago by skilled artisans still adorn the walls and can be admired today. Later, in America, the old-time craftsmen who made their own paints and colours were greatly assisted when premixed paints became available in a range of popular colours from local Hardware stores in the 1870’s. While the heavy oil bases dictated the range of available colours – the world became a more colourful place. The spread of this idea and the creation of “take home” cards with square samples of the available colours attached, helped kick off the modern DIY revolution. Around this time, the hundred or so available colours seemed to cover the needs of the average consumer.
But, in the Colour business, new fortunes have regularly been made through technological change and with the commercial tinting of white paint in-store from a range of pigment colourants the colour offering expanded a thousand fold. With modern tinting – almost any colour imaginable became available. The coloured cards previously given away to clients were now supplemented with wall mounted racks filled with hundreds and hundreds of small coloured chips. The number of colours presented was limited by the number of chips that could fit into the rack. Size seemed to matter and in 1992 the Dulux Master palette would offer 6,134 colours. The offering was so large it was presented in a huge colour atlas and with 126 colours per page – and 47 pages of different hues!
Now, it was possible to tint almost any colour, and the range of colours presented to the customer seemed only to be limited by the number of colour sample chips on display. A new way to expand colour offerings was needed and science came to the rescue. The in-store spectrophotometer was the answer. Samples of any coloured object that could fit into the spectro-device could likely be measured and formulated as a paint colour. Whether it was carpets, curtains or garden leaves – it could be matched! After 30,000 years, here was the Holy Grail of paint colours selection – you could now make whatever colour you wanted! Or was it? No- it was not!
Science had expanded the range of possible colours – but good taste and sophisticated choices lay not in the realm of Science!
The great couturier Christian Dior was once asked what was his formula in proportioning the perfect amount of Navy to Camel in a stunning co-ordinated outfit he had just presented? Dior pointed to his eye and then to his heart – and replied: “there is no formula – this is not science – this is Art!” He summed up what so many knew. Cave men at Lascaux in France 30,000 years ago created masterpieces still highly regarded today - from a simple palette of the few available colours. Having a huge palette of colours may assist the “Artist” – but it does not make him an artist. Any fool can create a disaster!
The greatest assistance to date for consumers needing to select paint colours has been the invention of the “paint colour visualiser”. Using modern computer graphics and a digital camera – a user can now view a library of rooms [or their own rooms from home] and observe the effect different colours make on the scene – and all in an instant. There is no guess work or imagination here – but a coloured representation of how the image will look in any combination of colours – in an instant. For the person with a flair for design creating beautiful combinations has never been easier. And for those more colour challenged – a range of designer schemes and inspirational colour photos are only a click away. This new tool not only allows any combination of colours to be put side by side and compared, but also the scale and different proportions of colours can be evaluated. For both the Paint manufacturer and the artist – here is a dream come true – to see your room painted – before lifting the brush.
Unfortunately, something appearing so simple, which is built upon a number of logical levels of colour science is relatively new digital colour science - and can be confusing even to experts involved in other areas of colour science.
The most common problem occurs when someone compares the “actual” paint colour to that on the monitor and discovers - they don’t match!
Before burning our colour scientists at the stake – some education is necessary.
Why Digital and Physical Paint colours should not match.
In 1997, when total sales for the paints and coatings industry were approximately $16.4 billion, at Autech Research, we were exporting “paint colour visualisers” to paint companies overseas. They were buying technologies we had only pioneered a few years earlier. Today, people from jungles in Vietnam to penthouse apartments in New York, use our software to choose colours.
At Autech the colours we generally use are scientific digital values or NUMBERS! (We use CIE XYZ’s to two decimal points and for viewing at illuminant D65). We use spectrophotometers for measuring and capturing colour, light boxes for viewing colour, and expensive calibrated monitors for displaying colour. A number of instruments and software applications confirm or warn us of the validity of any colour profiles used to check that our colours are being handled correctly. The “Human Eyes” in our office are the least trusted scientific apparatus in the building, being unreliable and primarily used as an early warning system to check instruments if something “looks wrong”! Alternatively, “Human Eyes” are used at our office to evaluate the beauty and artistic side of software interfaces and designer colour schemes.
Recent technology advances in digital image acquisition, colour-processing systems, colour printers, and other photographic input/output devices have been little short of remarkable. As well as ever-higher resolutions, the range and depth of colour reproduction has also shown significant improvements. A standardised colour space offers the benefit of consistent colour reproduction across all digital platforms and devices - the so-called colour workflow - from the point of acquisition to the point of delivery. Accurate colour consistency in an “as large as possible” colour space is required for professional users from the DTP and colour-proofing areas, as well as for the use of special devices for image processing and also industrial 4-colour printers. NEC’s SpectraView Reference 21 is an example of the Super Advanced Super Fine Technology (SA-SFT) Dual-IPS panel and LED backlight technology available today. NEC claims this expensive display technology covers more than 100% of the Adobe® RGB colour space and ensures absolute colour accuracy in all areas of colour processing on the monitor.
Colour scientists know that when comparing the colour of a paint sample held in one’s hand or placed on a bench top in front of the monitor should not match the same colour being displayed on a coloured display screen. A problem is that the average person expects the colours should match! [A visual match may be simulated under strict laboratory conditions using a light box and calibrated equipment, and then, usually at a theoretical light source!]
Why don’t they match? They don’t match because colour is dependent on light [illumination], whether reflected or emitted. For most designers and non-scientific colour experts comparing colours displayed under two different illuminants was likely an alien experience prior to the introduction of colour visualisers. The following “lay explanation” is to help those not from a scientific background to understand why those sample and screen colours don’t match.
A monitor is a display device usually set for a known illuminant, and for many modern monitors, LCD’s and Plasmas today, the sRGB colour space at D65 is a default display illuminant. On the contrary, the paint colour sample is likely viewed in a room where the illuminant is unknown and variable. The two viewing conditions are therefore unequal, and the appearance of the two colours by a single observer will not appear the same. In the room, the unknown lighting conditions could include be fluorescent, incandescent and any combination of other lighting sources including daylight and reflected lighting. The following image, image 1, is an example of a typical room – and a combination of different lighting temperatures is obvious where they wash across a single paint colour. The result is the single paint colour appears to vary all across the image!
Image 1.
To illustrate the point, here some random samples of the same off-white colour selected from a photograph demonstrate how the temperature of the lighting across the wall surface differs. The extreme example is in the room upstairs where an absence of light makes the off-white sample appear black. Because light changes colour and physical objects, such as paint samples, we must agree the appearance is dependent on external light sources. Our computer screen on the other hand, is independent of external light sources – instead using its internal light source to create colours.
Lighting within different room is never even at any given time, and in a room lit by natural light the colours are never at any constant colour temperature; they are continually changing with the movement of the day light, be it ever so slowly.
Decorating and Colour Scheming
For those in the artistic world - the relationship between colours is more important than worrying about colours at varying lighting temperatures. You could attempt to alter your screen colours settings throughout the day in an attempt to resemble the changing light conditions on your paint colour samples at hand, but accuracy would be momentary, and the overall objective a futile exercise. Professional colour experts use colour visualisers as tools to test colours combinations and create colour schemes. Knowing that our decorating scheme colour combinations are accurate, pleasing and harmonious is the objective. And a pleasing colour scheme viewed at one light setting will likely be pleasing under most lighting conditions. This is because the harmonious relationship established between the colours will be preserved where the lighting changes occur as a global effect.
Printing accurate colours.
Today we are witnessing the greatest colour revolution the world has ever known. The printing and photographic industries have undergone fundamental change and digital colour is now displayed on High Definition TV, captured on digital Cameras and printed as RGB colour. Galleries such as the Tate Modern in London now offer their inventory as high quality on demand prints and “Giclee” art grows in importance as is offered as limited edition prints. Most paint colour visualisers today display their colour as sRGB colour: calculated for best viewing at the D65 lighting condition. Through clever colour science today we can profile almost any colour printer to print a best match of our paint colours displayed on screen, best when our colours are within the gamut of the printer output. In image 2, we have an example of a paint colour displayed on a paint colour visualiser screen being printed through an inexpensive $200 Epson printer [custom profiled to print optimal results].
The result printed on a cotton rag paper has been compared with an actual dry paint sample of the same colour in a D65 light box and they are seen as a close visual match. Using instrumentation, they have both been measured with a spectrophotometer and a colour difference (DE 2.0) recorded.
Image 2.
This result has been created with two distinct types of media – one printed and one painted. The printed sample is made up of four inkjet pigmented inks - Cyan, Magenta, Yellow and Black being sprayed across white paper. The other, the paint colour sample is made from four pigment colourants mixed into a can of titanium Dioxide, painted on a substrate and dried leaving the resultant film of paint. While these colours are a close visible match at illuminant D65 – the match degrades under other light sources, exhibiting metamerism. This is because the colours are from different materials and have a different spectral fingerprint.
Image 3.
Image 3 shows the different spectral curves of the two colours. When the spectral curves are different – this shows the colours to be different. While they may appear a close match under one light source, they may not match under another light source.
Images 4 and 5 confirm the printed and painted colours metamer under the theoretical Illuminants A and F2 . The Delta E difference between the colours grows to DE 4.7 under Illuminant F2 – to DE 7.7 under Illuminant A.
Also, measured numerical values of the paint sample colour have changed under the different Illuminants. Image 4 and 5 demonstrates how the colour appearances have changed, and why comparing colours under different Illuminants will guarantee a visual mismatch.
Image 4.
Image 5.
As you can see, science can explain what may be misleading to the average person. It is easy to understand and appreciate the reverence, mystery, magic and respect our ancestors placed on colour when they discovered the magic of painting. The study of colour is both an art and a science.
Conclusion.
The majority of people are not scientists, and many wrongly believe colours and their properties are fixed: that is that Red is Red – and not Black once the lights are turned off! For the average person confronted for the first time when viewing a paint colour sample and an accurate onscreen display of the same colour; they will likely assume the onscreen colour to be wrong! Where the same paint colour is compared under different lighting conditions, the same colour must look different. For many of us this concept will at first be difficult to comprehend. But, in the future decorators, designers and artists will place a greater reliance on digital colour, as colour management gains importance in work flows. The ability to understand and explain perceived discrepancies in colour appearance will grow easier as online colour, and the use of digital tools, becomes more common place. For me as a human – the magic of colour is in its beauty – not in the maths – and as long pleasing and harmonious relationships are created – it is art I will worship – not the science.
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