Lighting Technology Glossary
What are the key terms for lighting design?
When designing lighting, mastery of technical language is not a theoretical exercise, but an operational tool. Terms such as luminance, UGR, colour temperature and CRI do not simply describe the characteristics of light, but guide design choices, influence the perception of spaces and determine the quality of the visual experience.
Novalux Lighting Technology Glossary
This Lighting Technology Glossary, compiled by Novalux, was created as a reference for professionals who work in the world of lighting on a daily basis: lighting designers, architects, interior designers and planners, who need a shared vocabulary that is up to date and consistent with current regulatory and design standards.
Illuminance (Lux)
Illuminance measures the luminous flux that falls on a surface and is expressed in lux (lx).
It is one of the fundamental parameters in functional lighting design, but it must always be interpreted in a perceptual and spatial context: a correct lux value does not automatically guarantee visual comfort if it is not supported by adequate light distribution and glare control.
Luminance (cd/m²)
Luminance describes the amount of light perceived by the human eye that is reflected or emitted by a surface.
It is the parameter most closely linked to visual perception, contrast and the legibility of environments. In architecture, luminance control is crucial to avoid visual imbalances and fatigue, especially in environments such as offices, retail or museum spaces.
Luminous flux (Lumen)
Luminous flux, expressed in lumens (lm), represents the total amount of light emitted by a source.
In professional lighting design, the lumen value is only the starting point: what really matters is how this flux is distributed in space, through optics, reflectors and control systems.
Luminous efficacy (lm/W)
Luminous efficacy indicates the ratio between the luminous flux emitted and the power absorbed.
It is a key parameter in projects focused on energy sustainability, but it cannot be evaluated in isolation: high efficiency must always be balanced with colour quality, visual comfort and the durability of the lighting system.
Colour temperature (CCT)
Colour temperature, expressed in Kelvin (K), defines the hue of the light emitted by a source.
In professional contexts, the choice of CCT is a strategic design decision: it affects the perception of materials, the circadian rhythm and the overall atmosphere of the space. Increasingly, advanced projects integrate tunable white or human-centric lighting systems, which overcome the static nature of a single colour temperature.
Key terms for lighting design
Colour rendering index (CRI / Ra)
The CRI (Colour Rendering Index) measures the ability of a light source to faithfully reproduce colours compared to a reference source.
For professional applications – retail, hospitality, museums, residential environments – high CRI values are essential, but they must be interpreted in conjunction with other more advanced indicators such as TM-30 for a more accurate colour assessment.
UGR – Unified Glare Rating
The UGR is the index that quantifies glare discomfort, i.e. the annoying glare perceived by the user.
It is a fundamental regulatory parameter in workplaces and public spaces, but also a design tool for improving overall visual quality. Proper UGR management involves optical choices, lighting fixture positioning and luminance control.
Light distribution and photometric curves
Photometric curves describe how light is distributed in space by a luminaire.
Correct interpretation of photometric diagrams allows designers to predict the actual behaviour of light, avoiding oversized or ineffective solutions. In this sense, lighting design is always a balance between technical data and design vision.
Light control and management systems
DALI, DMX, KNX and advanced wireless systems are no longer accessories, but an integral part of the design.
Light control allows scenarios to be adapted to the different functions of the space, optimising consumption and enhancing the architecture over time, transforming the lighting system into a dynamic system.
A shared language for quality light
Knowing and using lighting technology terms correctly means designing better, communicating effectively with all project stakeholders and creating consistent, measurable and high-quality solutions.
The Novalux glossary is part of this vision: not as a simple list of definitions, but as a cultural and design tool, designed for those who consider light to be an architectural material in its own right.