Lighting quality is the sum total of all lighting quality features. For good lighting, a lighting installation needs to take account of every relevant quality feature and not be designed on the basis of just a single criterion such as illuminance.

Reading a book, assembling intricate components, working at a computer – the visual tasks our eyes need to perform in our private and working lives are defined by a range of different activities. These different tasks present different lighting quality requirements.

Each one relates to a specific quality feature:

• lighting level determines brightness
• glare limitation makes for vision free of interference by direct or reflected glare
• harmonious brightness distribution ensures an even balance of luminance
• light colour defines the colour appearance of lamps, and in combination with
• colour rendering makes for correct recognition and differentiation of colours and defines room ambience
• direction of light and modelling determine how well we recognise three-dimensional forms and surface structures.
  
  

Visual performance, visual comfort, visual ambience

Depending on the use to which a room is put and/or the visual impact it is required to make, quality features need to be weighted differently to ensure maximum lighting quality. The emphasis may be on:

• visual performance, which is influenced by lighting level and glare limitation
• visual comfort, which is determined by colour rendering and harmonious brightness distribution
• or visual ambience, which is affected by light colour, direction of light and modelling.
  
  

The European standard DIN EN 12464 "Lighting of indoor work places" amplifies the concept of quality. On its introduction, the list of traditional quality features was extended to include daylight utilisation and energy-efficient light generation.