The renaissance of light

In 1850, when Queen Victoria was given the Koh-i-Noor, the largest and most significant diamond in the world at the time, she complained that it lacked sparkle and had it recut and polished. Despite reducing the size of the “Mountain of Light” – the English meaning of the Persian name Koh-i-Noor – by almost half, the new cut made the light refract more brilliantly and increased the stone’s value. A diamond’s beauty and value always depends on its effect. Lighting pioneer Ansorg applies the same basic principle to all retail lighting scenarios. In order to measure the visual effectiveness of lighting concepts and meet the requirements of increasingly individualised sectors and retailers, Ansorg has developed a new performance indicator. ROL, which stands for Return of Light, has the potential to replace the highly technical Light Output Ratio, or LOR, as a measure of luminaire performance.

It’s about what you get, not what you lose

LOR measures the effectiveness of a lighting scheme. The measurement is taken from the outside edge of a luminaire and it tells us what percentage of the light is output.However, it doesn’t tell us anything about how much light actually illuminates the merchandise, even though that’s an essential aspect of retail lighting performance. A retail lighting scheme has to efficiently guide the light so that it highlights the products and the consumer’s brain registers them because they catch the eye.

Return of Light or ROL is a more practical performance indicator that Ansorg has developed to measure retail lighting effect and efficiency. “By using ROL as an established performance indicator we are bringing research and development into line with the practicalities of a retail environment,” said Volker Knauff, Head of the Ansorg Product Design Center. “LOR is good for a comparison of luminaires in the laboratory, whereas ROL additionally measures efficiency in terms of how much light is available for product illumination.” ROL tells us what proportion of light reaches the target surface, i.e. the light that is directly available to the consumer to see the merchandise, rather than how much light is emitted from the luminaire. This slight shift in perception has wide-reaching impacts in practice because Ansorg has recognised that a luminaire with a good LOR doesn’t necessarily provide effective lighting.

Reflectors are the cut-diamonds in retail lighting

The diamond’s cut performs the same function as the faceted reflectors in retail luminaires. Both are the decisive elements that focus the light and refract it in the right direction. The reflector cut-out opening is significant. Low reflectors capture more light and efficiently direct it onto the target surface whereas flat reflectors with larger cut-out openings emit a greater amount of direct light that is diffused in the room rather than directed onto the merchandise, so it is wasted. Yet flat reflectors always have a better LOR simply because more light escapes from them, which is misleading and creates a false impression of efficiency (see Info box 1 below). 

This design-related effect made Ansorg’s Volker Knauff wonder whether LOR was still contemporary as a performance indicator (see Info box 2 below). He concluded that although it is still valid as a means of comparing several luminaires, Return of Light,ROL, is a far better indicator of efficiency and effect in practice.