Metamerism: Seeing the light on color management challenges

April 18, 2019

Metamerism has a huge impact on color reproduction. If you understand this phenomenon, then you’re ideally placed to handle its effect on color management – and to improve the accuracy of your print output. Print Service Providers (PSPs) can combat metameric mismatch easily with Device Link profiling, but it helps to know what metamerism is and how it works, first.

WHAT IS METAMERISM?

If two color samples seem to be identical under one light, but there’s a difference when they’re exposed to another set of lighting conditions – that’s metamerism.

How humans see color is primarily dependent on the reflectivity of a material, the colors perceived by each individual and – importantly – the light source. Different wavelengths of light are responsible for different colors. When they hit an object, some are absorbed; others are reflected – it’s the reflected wavelengths that are responsible for the colors we see.

However, the situation changes under different light sources. Those light sources will be emitting a range of varying wavelengths. For example, a pair of green socks viewed under a fluorescent light (emitting red and blue wavelengths) will appear differently when viewed in natural daylight, which emits red, blue and green wavelengths.

HOW DOES METAMERISM AFFECT COLOR MANAGEMENT?

Print businesses are all too aware of metamerism. Due to pigmentation differences in inks, PSPs may find the output on one printer doesn’t match another under different lighting conditions, particularly if the same job is being printed across multiple substrates.

Metamerism brings heavy costs to a business, as time, ink and media are all wasted during the troubleshooting process to correctly match color under different illuminants.

If colors don’t match under certain light conditions, profiles must be adjusted until the correct combination of colorants is identified – minimizing the effect of metamerism, guaranteeing accurate color reproduction.

HOW CAN I RESOLVE COLOR MATCHING ISSUES CAUSED BY METAMERISM?

It’s almost impossible to achieve this by eye. Thankfully, advanced color management tools can do all the work for you by using different algorithms (profile variants) during the profile calculation to account for different lighting conditions.

CMYK to CMYK conversion can help to improve color accuracy in the face of metamerism. This direct conversion method is used to create Device Link profiles, preserving the K-channel when reproducing color. A strong black channel can improve a job’s resistance against illuminant changes – resulting in less metameric color degradation.

Adapting colors to changes in light to produce different output variants requires simulating different lighting conditions. This can be achieved using a Light Adaptation Tool (LAT) in color management software, which provides a variety of actual viewing conditions outside normalized D50 daylight to guide color tuning. LAT allows for shifts in hue to the gray balance to enable a neutral gray under a specific light. Printing yellow, green, cyan, blue, magenta and red variants and comparing these with the original profile enables printers to pick the desired gray balance to suit the display lighting condition.

Metamerism is just one of many challenges facing PSPs looking to achieve absolute color accuracy across printers and substrates. By using the latest color management technology and Device Link profiling, print businesses can overcome this costly phenomenon for matching color under any lighting condition.

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