Light Distribution Classification of Luminaires
In the world of sports lighting, the classification of luminaire light distribution is a crucial discipline. It not only affects athletes’ performance and spectators’ viewing experience but also relates to the efficient use of energy. Today, let’s delve into the classification of luminaire light distribution and its wonderful application in sports lighting.
I. Classification by Outgoing Light Flux: Luminaire Classification by CIE
The International Commission on Illumination (CIE) classifies indoor luminaires into five categories based on the proportion of luminous flux emitted into the upper and lower hemispherical spaces: Direct, Semi-Direct, Diffuse, Semi-Indirect, and Indirect.
| Classification | Light Intensity Distribution Characteristics Upper Light Flux | Upper Light Flux Distribution (%) | Lower Light Flux Distribution (%) | Explanation | |
| Direct | Most light is emitted downward, directly illuminating the working surface. | 0 – 10 | 90 – 100 | Highest luminous flux utilization; prone to creating hard shadows. | |
| Semi-Direct | Upward light flux can reduce shadow harshness and improve brightness ratios of indoor surfaces. | 10 – 40 | 60 – 90 | – | |
| Diffuse | Relatively balanced upward and downward light flux distribution. | 40 – 60 | 40 – 60 | Used to create appropriate ceiling brightness; soft lighting effect. | |
| Semi-Indirect | Downward light flux is only used to create appropriate ceiling brightness. | 60 – 90 | 10 – 40 | – | |
| Indirect | Light is first reflected onto the ceiling and walls, then onto the working surface; soft light with no shadows. | 90 – 100 | 0 – 10 | Low luminous flux utilization. | |
In sports lighting, Direct luminaires are predominantly used, some equipped with reflectors, to maximize light projection onto the playing field and meet high illuminance requirements.
II. Classification by Light Intensity Distribution: Diverse Variations of Direct Luminaires
Direct luminaires are very commonly used, with a wide range of light distribution variations—from concentrated in a narrow beam to spread across the entire lower hemisphere. Different degrees of beam spread result in distinctly different lighting effects. Based on the narrowness or wideness of the distribution, they are categorized into five types: Very Narrow Beam, Narrow Beam, Medium Beam, Wide Beam, and Very Wide Beam, indicated by the maximum allowable spacing-to-height ratio (S/H):
| Classification Name | 1/2 Illumination Angle (θ) | Spacing-to-Height Ratio (S/H) | Characteristics |
| Very Narrow Beam | θ≤14° | S/H≤0.5 | Concentrated beam, suitable for long-distance directional lighting. |
| Narrow Beam (Deep or Concentrated) | 14°<θ≤19° | 0.5<S/H≤0.7 | – |
| Medium Beam (Diffuse, Cosine) | 19°<θ≤27° | 0.7<S/H≤1.0 | – |
| Wide Beam | 27°<θ≤37° | 1.0<S/H≤1.5 | – |
| Very Wide Beam | 37°<θ | 1.5<S/H | Large beam spread range, suitable for large-area uniform lighting. |
In sports venues, selecting direct luminaires with appropriate light distribution according to different sports and field sizes ensures uniform and adequate illumination of the playing area.
III. Classification by Beam Angle: Efficient Selection of Floodlights
Based on beam angle size, floodlights are classified into three main categories: Narrow Beam, Medium Beam, and Wide Beam. Larger beam angles correspond to higher luminaire efficiency.
| Classification | Beam Angle Range (°) | Applicability in Stadiums | Applicability in Gyms | Applicability in Gyms |
| Narrow Beam | 10 – 18 | √ | √ | ≥75 |
| 18 – 29 | √ | √ | 65 – 75 | |
| 29 – 46 | √ | √ | 55 – 65 | |
| Medium Beam | 46 – 70 | 〇 | √ | 45 – 55 |
| 70 – 100 | 〇 | √ | 35 – 45 | |
| Wide Beam | 100 – 130 | × | √ | 25 – 35 |
| >130 | × | √ | <25 |
In large stadiums, narrow-beam floodlights are typically chosen to illuminate distant areas of the field. In indoor gymnasiums, medium-beam or wide-beam floodlights may be selected to achieve uniform lighting effects.
Light distribution classification of luminaires provides a scientific basis for sports lighting. By rationally selecting different types of luminaires, we can create an optimal competition environment for athletes, offer an excellent viewing experience for spectators, and achieve high energy efficiency. With continuous technological advancement, it is believed that luminaire light distribution classification will become more refined, and the future of sports lighting will be even brighter.
