Good lighting design does not start with product; it begins with need: what emotional response does a professional lighting designer or architect want to stimulate in users of a space? What surfaces and objects should be lighted, at what intensity, to draw attention and shape spatial perception? How much light do users need on task surfaces to enable them to perform those tasks without headache, eye strain, glare or veiling reflections?

Good lighting design

Once these design decisions are made, light source and luminaires can be more accurately selected. The right luminaire for the job is often not the one that is most efficient in lumen output but, rather, in lumens onto worksurfaces or lumens on the ground or floor. Luminaire efficiency may be judged based on input watts, luminous efficiency, efficacy rating (lumens per watt) and a coefficient of lamp utilisation.

As luminous efficiency is published in most photometric reports and catalog sheets, designers often focus on this one metric. It is an important metric, telling us the percentage of light produced by the lamps in a luminaire that is, in turn, emitted by the luminaire. But it only tells part of the story of luminaire performance. Overemphasising it can lead to ultimately weaker or improper lighting choices for applications at hand.

After all, a bare lamp offers 100 percent efficiency but would not be a good choice in, say, a classroom. The most efficient luminaires－particularly unshielded luminaires with direct light distribution－can easily be “glare bombs” when installed with clear or no lensing, in applications with lower mounting heights, or by simply installing too many fixtures. Attention to lighting choices and their design can result in luminaires that are not only energy-efficient and energy-saving, but provide more effective lighting solutions for offices, classrooms, stores, public spaces and grounds.

Application-efficient lighting, as contrasted with output efficiency-only criteria, is judged by entirely different goals:

• It provides adequate and proper light levels for good task visibility, and performance in specific applications;

• It distributes uniform illumination where needed, with shadow and contrast for interest;

• It maximises visual comfort by minimising glare, including irritating reflections on computer screens;

• It renders colours and skin tones naturally.

This is a social necessity

We need light to develop our activities and to create security. The basic need of lighting is to illuminate a space, full of light in general. In many underdeveloped countries and even in some parts of the developed countries, the only approach of lighting is: a bulb or a fluorescent light in the ceiling of a room.

It is light to see. However, concerning spaces, it is important to communicate them. To do this we must create hierarchies of light levels and emphasise its architectural peculiarities, order, and rhythm. To generate both emotion and surprise aesthetically, it is light to watch and contemplate, and even to delight. This is the present situation of most lighting design projects. Emotion is generated through order and rigour. Today, the projects are composed of two core “ingredients”.

The technical aspects such as consumption, lamp life (in hours as in performance), colour temperatures, type of luminaries to be used, accessories, and control systems are measurable data, easily manageable with the possibility of regulating standards. The aspects that will set values for items include efficiency, sustainability, maintenance, etc. And of course the subjective aspects, which are as important or more than technicians, even if more difficult to define, quantify and include in legislation. In the metaphor of an iceberg, the technical aspects represent those parts of it that remains above water.

They are visible, measurable and quantifiable. Instead, the subjective aspects would be those parts of it that are under water. We know that it is the most part of the block of ice, but we can not see, and we do not know its shape… Though we are developing tools to acquire knowledge about with all our accumulated experience.

We have very well solved the technical problems, and further developed to have better characteristics, but the subjective part is not the object of major studies and developments because it does not provide economic benefits, at least for now. The technical aspect of lighting projects has experienced significant development, but this is done by, for example, engineers. We, as lighting designers should incorporate this technical development to the subjective part, which we define as the added value of the project