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WHY DO COLOURS NOT ALWAYS LOOK THE SAME?

INTRODUCTION

One of the main challenges when reproducing artwork is to match the colours of the reproduced print to the original piece. Even in this age of advanced technology, this is easier said than done.


At Studio74, we work with finely calibrated, high-end equipment and apply our many years of experience in giclée printing to give near perfect results. Our skill of digitally modifying scanned images to make them look as close as possible to the original is the hard work that sets us apart as a business and enables us to produce prints that our customers feel accurately represent their art.




A SPANNER IN THE WORKS


So, we’ve done our best to create perfect images in the studio for our valued customers. This means that both artwork and print will look almost indistinguishable when viewed side by side underneath our specialised light source that represents almost every visible light frequency that the human eye can see (an estimated accuracy of 98% Colour Rendering Index (CRI)). When the customer comes to view the results, we’ll make sure to present it to them under these optimum lighting conditions.


The customer is happy, we’re happy – job done?! Maybe. Let’s assume that the customer gets home and takes another look at the perfect match that we managed to create. All of a sudden they may find that things look slightly different. Here enters the phenomenon that is referred to as Metamerism.


Imagine you’re getting dressed in the morning under low lighting and you throw on a pair of black socks. Then, when you arrive at work, you realise that one of them is navy blue. This is another example of metamerism.


THE BASIC PRINCIPLE OF METAMERISM

Metamerism is a complex subject with a large number of instances and consequences, but what matters for our customers who are commissioning fine art prints is this basic principle:


Metamerism occurs when the colours of two different materials match under one type of lighting but not another.


HOW DO WE SEE COLOUR?

To understand this phenomenon, let’s take a step back and find out how colour is produced.


When light is projected onto a surface, it will either be absorbed by or reflected back from the surface. The colours we see are a mixture of those light frequencies that bounce back from the surface.


COLOUR AND DIFFERENT MATERIALS

Now we’re going to add a bit of complexity. When two different materials are exposed under the same light, they will absorb and reflect this light differently. We call this the unique colour footprint of the material.

Going back to our printing scenario, it is now starting to become clear why our perfect print didn’t look so perfect after changing the light source. First of all we adjusted the print digitally to make it look the same as the original artwork under our professional studio lighting. Then we looked at both under a different light (where some colours were either under or over represented). Unlike our studio lighting, incandescent light (typically used in the home) has a higher level of energy in the red area of the spectrum, meaning that an object will appear redder than it will under our studio light. At first glance we could have assumed that it should have affected both original and print in much the same way and therefore they should both still look the same but we now realise that the light reflectance and absorption of the two materials differs because of their unique colour footprint.



CAN METAMERISM BE AVOIDED?

In our case, not really. One way to circumvent metamerism would be by using exactly the same pigment and substrate compositions in the reproductions as the ones which were used in the original. Unfortunately we don’t have this luxury as we have no control over the wide range of artwork brought to us. Therefore, the best we can do is to work under the best possible light, which represents the highest match to the visible spectrum of colour, but it still means that variation can occur when viewing both original and print under less than perfect lighting conditions.


We believe that giclée prints are best viewed under the ‘older’ colour temperature standard of 5000K (Kelvin) for colour accuracy. Officially, the optimum colour temperature standard is 6500K (apparently measured in Norway at noon on a cloudy day!), but this is focussed on outside daylight conditions, whereas our slightly more yellow standard is more suitable as most artwork is viewed indoors, at home or maybe in an exhibition environment.


FINALLY – JUST TO CONFUSE YOU

We’ve concentrated on the light source and the surface material, but how about us, the observer? Does our eyesight have an influence on how we see colour?


“Observer Metamerism”, also known as “Observer Metameric Failure”, occurs when we (the observers) have differences in the way we see colour.


A common source of observer metameric failure is colour blindness, but metameric failure is also not uncommon between observers for other reasons. For instance, the proportion of long-wavelength-sensitive cones to medium-wavelength-sensitive cones in the retina, the profile of light sensitivity in each type of cone, and the amount of yellowing and clouding in the lens (cataracts) and macular pigment of the eye, differs from one person to the next. This alters the relative importance of different wavelengths to our eyes and brain and, as a result, changes our colour perception. Basically, all this means we all see light differently, which adds another dimension to the topic of metamerism.


I feel another blog coming on, but not today!



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