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Me Mu

Metamerism

The term metamerism is understood as the effect that two things may look the same under one light, but completely different under another light.

In practical terms can be mooring at an example: If a yellow sheet of paper and a sheet of white paper under yellowish light are considered, both appear the same. If the same sheets are viewed under white light, one sheet is white, whereas the other sheet is yellow, so a completely different color.

This metamerism can especially occur very strong, if different colors and methods are used for the production. The gray of a proof is often made of several inks of the 11-color proofing systems, while a neutral gray in an offset print ist often made from only one color: black. The risk of color shift is therefore higher for the proof than for the pure black in offset printing. Even in colorpatches of fabrics and prints strong metamerism may occur.

Lighting can also be a reason for metamerism. A perfect proof-to-print-match unter D50 standardizes lightning might well be, but under sunlight with UV influence or incandescent light in the evening there can be huge color deviations because of metamerism.

 

multispectral

In order to describe colors accurately and avoid metamerism, modern color measurement is increasingly no longer carried out via colorimeter that can measure one color spot in the 3-dimensional colorspace LAB, but by spectral measurement, ie the recording of the complete emission spectrum or reflection spectrum of a color.

Even with cameras, this technology is used. So images are no longer to be photographed in RGB, but with systems such as the Can:View, images can can be photographed in 16 individual spectra between 400 and 700 nm with 11 million pixels. Each of these pixels is thus defined spectrally.

In retouching, one type of light can be used, D50 or D65 for example, and – since the spectrum of the illuminant is known – the image can be easily processed by the multi-spectral data with a mouse click on the required standard light for retouching.

At present, with the can:view (softproof system) and the can:scan (camera system) a complete system is on the market for recording and edition images with multispectral data. Outside catalog manufacturers and fashion companies, the technology has not yet arrived in the broad market.