And then there was light…

Jill Entwistle reports on updates to lighting products creating artificial daylight, and indeed offering night time scenarios too

Quite simply, nothing is better than natural light. The drive in any new building or refurbishment should be how to introduce as much daylight as possible. It is essential to human wellbeing and, as a free source of energy, more sustainable.

But there are spaces in buildings where the introduction of daylight is logistically difficult or impossible, from basements in shops or hotel spas, to offices at the core of a deep-plan working environment.

Which is where the artificial skylight comes in. They have been around for many years, of course, originally using standard fluorescent tubes, then tubes of different colours or colour temperatures, linked to a control system to simulate the variations of daylight.

As with so much in lighting, LEDs have made the whole business somewhat easier, allowing much more accurate colour calibrations, as well as being infinitely easier to control so that the colours and shifts in temperature are more subtle.

It is one of those areas which is open to some very indifferent designs, to put it charitably. At its most basic level, sidelighting a piece of glass with some cool white LEDs isn’t rocket science. There have also been infelicitous attempts with images of the sky superimposed.

They are obviously a far cry from the technically exacting processes of the systems featured here, which resulted from extensive research into optics and the dynamic and colour qualities of natural light. CoeLux has featured before on these pages, and the examples are the latest updates to a pricier technology 15 years in the development and that stands alone in its approach. Finnish company Light Cognitive is newer to the field, and is only now available in the UK, but also rooted in rigorous attention to detail.

CoeLux LS

The latest manifestation of the CoeLux concept is the CoeLux LS (Long Sky). The new system is double the size of the ST model and can reproduce the changing features of the sun to create different scenarios: sun, endless bright-blue sky, soft white clouds, and the effect of sunlight filtering through clouds creating contrasts and shadows.

The biggest CoeLux systems have a Switch to Moon mode, rendering the product as a window facing a full moon in a dark skyThe biggest CoeLux systems have a Switch to Moon mode, rendering the product as a window facing a full moon in a dark sky

Designed to be installed in any kind of false ceiling, the LS system has a bigger opening compared to the solid models: the size of the window is 29.5cm x 108.6cm and it can be installed as a single unit, as a modular system, or aligned in order to design hallways of light in the darkest rooms. It features a dimming system that allows the modulation of light intensity.

It is available in two versions, CoeLux LS Matte and CoeLux LS Ice, featuring their own finish and frame size. The LS Matte features a 13cm-high frame. The sun reflected on the matte white frame creates a 45-degree sliver of light.

CoeLux LS Ice features a 10cm-high frame. The sunlight reflects on the frame creating a 45-degree sliver of light plus a sliver of light in the opposite direction. It is designed for spaces that need animated light: the sun reflected on the frame is visible from various angles. It suits offices and shops, where the double sliver of light can dramatically light up shop windows and the shop itself simultaneously.

As with all CoeLux systems, the technology is unique in replicating the effect of Rayleigh scattering, the optical phenomenon named after British physicist Lord Rayleigh – in simple terms, the scattering of sunlight in the atmosphere that causes diffuse sky radiation, and is the reason for the blue colour of the sky and the yellow tone of the sun itself. It’s the result of the 15-year, partially EU-funded, research by Professor Paolo Di Trapani, physics lecturer at the department of science and high technology, University of Insubria in Como.

The system features three main elements: LEDs to reproduce the sunlight’s spectrum; an optical system that creates depth; and nano and micro particles that accurately reproduce the features of the atmosphere, depending on the movements of the viewer. The light clouds do not prevent the sun from breaking into the scene to soften contrasts and shadows. To perceive them, the viewer needs to look towards the sun: they slightly move to give way to the bright blue sky.

The Switch to Moon mode is also now available in the biggest CoeLux systems, CoeLux 45HC and CoeLux 60HC, allowing an easy switch from the day scenario to the night one. A soft light will shine on the objects and on the ceiling it becomes a window facing a full moon in an endless space


Already on the market is the EWINDOW from WindowLux, which offers full-spectrum lighting that also transitions from cooler light temperatures in the morning to warmer tones in the evening, like other systems, supporting circadian rhythms. Winner of the 2017 China Innovation and Entrepreneurship Competition, it has three means of control: wall-mounted controller, Dali, or mobile app (Android and iOS). It can be set to automatically synchronise with the local daylight cycle (through GPS). Manual control allows presets or custom-set brightness (up to 7300lm) and colour temperature adjustment (between 2500K and 10000K). It also has a high CRI of up to Ra98.

Using micro optics on the diffuser, the system emits one focused lighting beam with higher intensity and a wider light beam at lower intensity, producing the effect of combined direct sunlight and dispersed ambient skylight. It is available with surface mounted or recessed frame, with the option of a customised finish.

Big Sky
Light Cognitive (Available In The UK Through Fjor Light)

The Finnish company has worked with Dr Steven Lockley of Harvard Medical School to develop its Big Sky system, featuring its patent-pending Natural Daylight Creation technology for high-fidelity dynamic sky view, from dawn to dusk.

Satisfying the criteria of the WELL standard, it reproduces the natural light spectrum and has very high colour rendering, up to Ra98. The LEDs are controlled by Light Cognitive’s specially developed control system. Big Sky is oT-enabled and controllable over Wi-Fi.

Light programmes are accessible using an app available on any smart device. So far there are three options: Big Sky Horizon, Big Sky Dome and Big Sky Limitless, all of which allow the products to be manually set to different light scenes. If users want a dynamically changing light over the day, the Sky Player feature is required. This allows users to select sunrise and sunset times, press ‘play’ and the system will run through their personal daily cycle.

Big Sky Horizon is the easiest to install in that it doesn’t have to be integrated, but can be hung on a wall like a painting. It creates a pleasant view into the horizon, rather like looking out from a skyscraper or an airplane window.

Attached to the ceiling as a skylight, Big Sky Dome is designed to create general light fields. It generates a sky view upwards and its soft immersive light surface promotes a feeling of space. The option is designed for transforming any space where structural changes are not possible.

Big Sky Limitless is the company’s large custom solution completely replacing general lighting. Using stretch ceilings, it enables light fields of any size. Like all the options, Limitless is tunable with all hues of the sky.

Progressive Media International Limited. Registered Office: 40-42 Hatton Garden, London, EC1N 8EB, UK.Copyright 2024, All rights reserved.