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A history of task and spot lighting

ONLINE VIDEO 8 July 2011

This video timeline by Thomas Schielke covers a fascinating selection of the first LED luminaries for interior lighting. The first decade with white LED light reveals how designers have implemented new technology in existing housing, added LED as part of a product group or created a unique design specifically for LED.

The focus on task lights and spotlights vividly shows the dialogue between form and technology. In the beginning, low light output required short distances between the luminaire and the illuminated object as exemplified by a table and a task light. High power LEDs, which became popular around 2006, enabled longer distances as they occur with track fixtures on ceilings. Although LEDs, including colorful RGB LEDs in decorative fixtures, have been on the market for over 10 years, LED light in architecture started with white light for a good visual performance. The timeline includes international designers and architects like Norman Foster or Yves Behar and luminaires from 2001 up to the newest designs presented at the Euroluce 2011 in Milan.

Design: Minimal design for small LEDs.
The “El.E.Dee” design from 2001 by Ingo Maurer tells the story of an early experimental design with a bare LED board held by gripping pliers. In contrast to the small low-voltage tungsten lamps which have often been used for task lights, the tiny LEDs allow even smaller profiles (Brazo, 2006). Many designers were inspired by the miniature size of the LEDs and developed slender forms with minimal design (Line Z, 2006). A major change in the visual appearance of LED luminaries derived from the LED boards because a single LED would not emit sufficient light. Later, high power LEDs with a higher lumen output made arrangements with less LEDs or even with a single LED possible (Zufall, 2008). New technical challenges like thermal management induced high tech details ranging from an active cooling fan (Halley, 2005) to distinctive passive cooling fins (Lotus, 2006) to ensure a high lumen output and LED longevity. The visibility of LED dots is often used to form an expressive statement to differentiate the LED from traditional luminaires and to identify it as a modern fixture (Tempura, 2007).

Technology: New optical systems and thermal management for high performance.

The miniaturization euphoria about tiny 5mm LEDs was limited caused by the initial low light output. Good visual performance required a number of LEDs. Some designers handled this challenge by forming a row of LEDs in small but long profiles (Z-Bar, 2005), others with an array of LEDs (INA, 2008). The most critically technical aspect for designers was the thermal management of LEDs. If not designed correctly, it could lead to lower light output and shorter longevity. Designers also had to rethink their traditional optics approach to include reflectors to direct the light. Due to the specific light distribution of LEDs, systems with lenses can be more efficient. Changeable modular lens systems enabled different lighting distributions with one fixture (Logotec LED, 2011). New lighting features like changeable colour temperatures from warm white to cool white offered new features for designers. Thereby, the luminaires require a two-dimensional interface: One for brightness and one for colour temperature. To enhance the modern appearance some designers implemented smooth touch- dimmers to control the light (Leaf Lamp, 2006).

Despite the state-of-the-art impression of LED fixtures sales only increased slowly in the early stages due to financial and light quality constraints. The initial high costs of LEDs decreased with the upcoming mass production. In contrast to early high-prize luminaries in small series, it was once again IKEA who changed the market perception with a basic task light including photovoltaic cells for about 20 EUR in 2009. The early light challenges were caused by the low lumen output and the low colour rendition index which has drastically changed in recent times.

Energy: Saving energy with efficient lighting technology
Today’s high-power LEDs are of course much more efficient than the LEDs of the first generation. Early on, LED luminaires were used mainly as a general table light and not as a task light to meet the ergonomics standards of 500lx on the working area because the light output was too low. To raise the light output, designers increased the number of LEDs per luminaire. Later on, with the change to high-power LEDs the number of LEDs per luminaire declined drastically. State-of-the art warm white LED technology with a light efficacy of about 75lm/W just requires one third of energy for the same lumen output if compared to low-voltage tungsten lamps with about 25lm/W, thereby enabling task lights for offices with less than 10W. The longevity of LEDs with 50.000 hours facilitates a use for 20 years when used on workdays for 10 hours.

Outlook: Technical innovations and lifestyle as formgivers for future LED design
The history of LED lighting is relatively young in comparison to the tradition of incandescent fixtures, which has its roots in the late 19th century. Therefore, we can expect a lot from future developments. Designers and lighting engineers strive for more light by using the next generation of LEDs with higher lumen output, creating layouts with bigger LED light boards and designing specific lighting technology to efficiently direct the light. Higher LED lumen output will enable designs with more compact forms using less LEDs. However, physical aspects like thermal management sets limits to closely packed LED boards. On the other hand, optical films will inspire designers to minimize optical systems. These technical advances will lead to new application dimensions with higher illuminance levels and longer distances. The future will definitely bring many more unique LED design solutions – either technically orientated or influenced by contemporary lifestyles.


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