Blog

Nature of Light in Lighting Design: Complete Technical Guide for Professionals

Introduction to the Nature of Light in Lighting Design

Light is a complex medium with which to work. While light itself is understood by science, how humans perceive it remains not fully understood. Different people react to light in different ways. It is therefore important in Lighting Design to be sensitive to what people like and dislike about certain properties of light.

The Nature of Light in Lighting Design focuses only on visual light. Visual light is the emission of energy within a certain bandwidth range known as the visual spectrum.

---

Visual Spectrum (390nm–700nm)

The visible range of light generally lies between 390 nanometers (nm) and 700 nanometers (nm), although this may vary slightly from person to person.

Light can be:

• Received directly from a light source such as a lamp

• Seen as a reflection of other objects

The colour of objects is determined by the light reflected from their surfaces and received by the eye.

For official lighting standards and technical guidelines, refer to the Illuminating Engineering Society (IES).

---

How Light Travels in Lighting Design

Light travels in straight lines. This makes it possible to predict where light will fall within a room. In professional Lighting Design, standard mathematics can determine:

• Whether a light source will be visible

• Whether glare will occur

• Whether light will fall on a specific surface

When light travels through different materials, such as air and glass, its direction changes.

---

Total Internal Reflection

If light contacts glass at a very shallow angle, almost parallel to the surface, it will not penetrate it. Instead, it reflects away similar to a mirror. This is known as total internal reflection.

In some cases, it may not be possible to transmit light through glass elements, such as steps, if the light is positioned next to them.

---

Properties of Light and Electricity in Lighting Design

Understanding measurable properties is fundamental to accurate Lighting Design.

---

Luminous Intensity

 

Luminous intensity measures visible light in a particular direction per solid angle.

Most lamps with a beam angle (generally up to 60°) will have a peak intensity value. This allows comparison between lamps and indicates maximum light output.

---

Luminous Flux

Luminous flux measures the total visible light output of a lamp.

This value is commonly given for fluorescent tubes and incandescent lamps and allows comparison of brightness between different lamps.

---

Illuminance

Illuminance is the measure of luminous flux per unit area.

Typical Residential Illuminance Levels

A house would not be lit entirely at 500 lx, as this level is typically required only on work surfaces.

Manufacturers often provide light cone diagrams showing peak illuminance at different distances.

---

Power

Power refers to the electrical power used by lamps.

Lighting equipment has maximum wattage limits. For example:

• Many dimmer switches have a maximum rating of 250W.

• Exceeding this may cause overheating.

It is normally acceptable to have less than the maximum wattage unless using fluorescent or metal halide lamps, which must be correctly matched.

---

Efficacy

Efficacy relates to the ratio between lumens produced and watts consumed.

Some lm/W values consider transformer and ballast losses, as well as light lost within the fitting.

Higher lm/W indicates greater energy efficiency in Lighting Design.

---

Electric Potential (Voltage)

Electric potential is measured in Volts (V).

When purchasing lighting equipment from other countries, voltage compatibility must be ensured.

---

Current

Current is the flow of electric charge.

Power, Voltage, and Current are related:

Power = Voltage × Current

Some switches specify maximum current (commonly 10A) rather than wattage.

---

LED Current Requirements

LEDs generally require constant current to emit maximum light output.

Common specifications include:

It is important to obtain an LED driver that matches these requirements to ensure efficiency and prevent damage.

Internal Reference Pages:
 LED Lighting Products
Lighting Consultancy Services

---

Correlated Colour Temperature (CCT)

Correlated Colour Temperature measures the warmth of light.
Unit: Kelvin (K)

If a high level of light is required, cooler temperatures (3500K–4000K) are generally suitable.
If a lower level of light is required, warmer temperatures (2700K–3200K) are preferred.

If two light sources serve the same purpose, such as illuminating a work surface, their colour temperature should match.

---

Dimming and Colour Behaviour

This must be considered in professional Lighting Design.

---

Colour Rendering Index (CRI)

The Colour Rendering Index measures how accurately a light source shows colours compared to a black body radiator standard.

Sodium street lamps have very low CRI, making colour distinction difficult.

CRI is a critical parameter in both residential and commercial Lighting Design applications.

---

The Nature of Light in Lighting Design combines visual science, electrical principles, and human perception. From luminous intensity and flux to voltage, CCT, and CRI, each measurable property contributes to accurate and effective Lighting Design.

A clear understanding of these fundamentals ensures correct lamp selection, safe electrical planning, and appropriate visual performance across all applications.