Knowledge database of light, color, standard light

HOW YOU CAN assess your COLOR PROOF STATIONS

Together with our subsidiary GL Optic, we develop professional light measurement technology for a wide range of applications. One of them is the ISO 3664:2009 compliant light assessment of color matching stations with standard light D50. Find out here how you can measure and evaluate the standard conformity of your color testing equipment.

Capture light and take it back home...01 Capture light and take it back home...
How to do visual comparisons of coloured materials. According to ISO 366802 How to do visual comparisons of coloured materials. According to ISO 3668
ISO 12647-2:2013 COLOR CHANGES ARE NOT ALWAYS INTENTIONAL...03 ISO 12647-2:2013 COLOR CHANGES ARE NOT ALWAYS INTENTIONAL...
Soft proofing at work04 Soft proofing at work
Assessment of fluorescent materials05 Assessment of fluorescent materials
MUNSELL colour system
in standardised light devices06 MUNSELL colour system
in standardised light devices
Symmetrical or asymmetrical light design?07 Symmetrical or asymmetrical light design?
ISO 3664:2009
Colour matching in the graphic arts industry08 ISO 3664:2009
Colour matching in the graphic arts industry
DIFFERENCES IN LIGHT TABLES, COLOUR PROOFING LIGHTS AND COLOUR VIEWING STATIONS09 DIFFERENCES IN LIGHT TABLES, COLOUR PROOFING LIGHTS AND COLOUR VIEWING STATIONS
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Capture light and take it back home...

In conjunction with our subsidiary GL Optic Lichtmesstechnik, we have developed a process to reproduce exactly the light in a JUST standardized viewing booth that is measured before at any place. Find out how it works!

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How to do visual comparisons of coloured materials. According to ISO 3668

Measuring instruments are only one part of comparing and quality controlling colours and substrates. Since no technical device is as precise as the human eye, the visual colour control is still essential for accurate quality control.

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ISO 12647-2:2013 COLOR CHANGES ARE NOT ALWAYS INTENTIONAL...

ISO 12647-2:2013 takes into account optically brightened papers, which is why a significantly increased UV content has been set, which is more closely matched to daylight. This also affects the standard for color measurement ISO 13655:2009 and the standard for color matching ISO 3664:2009. But putting them into practice is already possible today! Print, measure and view your prints according to ISO 12647-2:2013.

Soft proofing at work

Time- and cost-efficient workflow solutions are increasingly being implemented in response to the constantly growing demands as regards delivery capability and pressure of time. Compared to a classical proof printed on production paper, or a digital hard copy proof, a digital soft proof on a monitor permits more cost-efficient reproduction of the original for subsequent production printing.

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So, while the original to be matched can exist in physical form, it does not necessarily have to. Under optimum circumstances, the original is actually the colour appearance described by the file. Of decisive importance in this context is colour-accurate display on a calibrated monitor, and the use of ICC profiles. The latter can be used for colourimetric characterization of the image data, subsequently permitting their colour-accurate reproduction on the press. The requirements for colour soft proofing systems are described in the latest version of ISO 14861:2015. The quality requirements for colour monitors suitable for soft proofing are defined in ISO 12646:2015. A colour matching booth with standardised light is prescribed as obligatory for colour-accurate visual comparison. The light conditions of the standardised viewing device basically comply with ISO 3664, but it must be possible to adapt the brightness to the limited luminance of the monitor. Our soft proof colour matching booths with USB interface feature software-controlled, exact adaptation to the brightness of the monitor. A high and stable quality of the soft proofs necessitates trouble-free interplay of the individual components within defined tolerances. Ask us for more detailed information on the subject of soft proofing.

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Assessment of fluorescent materials

Materials and surfaces can be made fluorescent by admixing optical brightening agents (OBAs). Optical brightening agents are fluorescent substances that absorb light in the UV wavelength range from 300 to 390 nm, and emit it in the adjacent spectral range from 400 to 460 nm.

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Materials containing added OBAs appear whiter or brighter and more luminous. They are used in some papers, textiles, detergents and plastics. A UV light source is needed to observe fluorescent surfaces. Depending on version, both our Color Viewing Light viewing booths and our multiLight colour proof lights are equipped with UV lamps, in addition to the standard illuminants. The simultaneous activation of D50 or D65 and UV permits reliable assessment of optically brightened materials. The visual impression is determined by the amount of OBAs used and the UV component emitted by the light source. Viewing jobs using UV light are frequently encountered in the textiles sector or in security printing. However, OBAs are nowadays also used in a wide variety of other materials, such as imitation leather, paints or films, meaning that their testing is also acquiring ever-greater importance.

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Color matching of fluorescent materials with UV radiation

MUNSELL colour system
in standardised light devices

The colour system devised by Albert Henry Munsell (1858–1918) was intended to represent colour samples in a manner corresponding to human perception for the first time. In other words: the visual distances between adjacent colour samples were supposed to be perceived as being equal.

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This gave rise to a three-dimensional body with a vertical value axis (black-white). Principal and intermediate hues are concentrically arranged about this axis in such a way that their chroma decreases towards the value axis. Derived from this, the "Munsell Book of Colour" contains colour charts that can be used for selecting and comparing colour samples. The ambient conditions have a major influence on colour assessment when matching coloured surfaces. That is why the viewing space of all standardised viewing devices from JUST is normally powder-coated in the reference colour Munsell N7, which corresponds to a neutral, matt gray. Compared to other Munsell colours, Munsell N7 displays the least metamerism and the slightest colour shifts when viewing under different illuminants. The JUST Color Viewing Light viewing booths are also optionally available in the neutral gray shades Munsell N5 and G5574.

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Symmetrical or asymmetrical light design?

JUST colour proof lights fundamentally offer a choice between a symmetrical or an asymmetrical light design. In a modern, symmetrical light, the rays of light are directed onto the viewing surface in diagonal, cross-over fashion ("cross-symmetrical").

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As a result, the observer's position is of no importance. He sees the same thing from all sides. In contrast to conventional, symmetrical systems, which guide the light directly onto the viewing surface in all directions, glare and reflections are almost entirely avoided. This solution is generally used in conference rooms.

The latest generation of asymmetrical systems offers even better characteristics as regards glare and reflections. So, if possible, preference should be given to a colour proof light with asymmetrical light design, since the rays of light are then not deflected towards the observer. In this case, viewing is performed from one side. Consequently, all viewing stations from JUST Normlicht are equipped with an asymmetrical light, since viewing is only performed from one side on these devices.

How do you identify the light design of a colour proof light?
Products with the letters "AS" are asymmetrical lights (for viewing from one side), while those with the letters "CS" are symmetrical lights (for viewing from several sides).

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asymmetric

symmetric

ISO 3664:2009
Colour matching in the graphic arts industry

The valid ISO 3664:2009 standard regulates the viewing conditions for the colour proofing of originals and reproductions in the graphic arts industry. The users are photographers, advertising agencies, classical prepress businesses, and printers on the press. The ISO standard essentially defines the requirements for the viewing conditions, test methods, and both obligatory and recommended targets to be achieved.

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DIFFERENCES IN LIGHT TABLES, COLOUR PROOFING LIGHTS AND COLOUR VIEWING STATIONS

When searching for standard lighting systems, one often reads terms such as light table, color proofing lights or color proofing station, which are frequently used synonymously. For JUST products there are differences between these products.

Light tables are luminous surfaces. They are available as smaller light tables without a frame (feet) and as large-format light tables with angle- and height-adjustable, luminous worktops. They are often used for quality control and translucent materials.

Colour proofing light are luminaires, which illuminate surfaces for colour proofing. Our colour proofing light products are pure luminaires for suspension from the ceiling or for mounting on gallows or similar.

Colour viewing stations includes a colour proof luminaire and a free-standing workstation. They have at least onestand, but usually also storage cabinets, compartments, and side walls to shield them from ambient light. Colour olour proofing station illuminates the proofing area and are used in the graphic arts industry in pre-press and at the press control console.

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