This is achieved with a semi-transparent dial and a luminous compound that causes all displays to glow in the darkness - with a distinctive green hue that the human eye perceives as particularly pleasant. The hour and minute hands are filled with the luminous material; the chronograph sweep seconds hand is fully coated with the compound. The seconds hand and minute counter in blued steel revolve above subsidiary dials that are noctilucent, too. The circumferential dial ring with the minute scale that is subdivided into fifth-of-a-second graduations, the concentric tachometer scale and the power-reserve arrow applique also glow in green.
But the real stunner is the luminous outsize date. Composed of two separate display elements, the outsize date is designed to glow immediately after the midnight switching sequence as well. This is made possible with a luminous ten cross and a black printed units disc made of transparent glass which rotates above a luminous background. Both elements must be able to recharge during the day when they are positioned beneath the dial. This is enabled by the semi-transparent dial; even during the day, it endows the watch with inimitable aesthetic appeal. Its coating not only assures crisp legibility in daylight but also allows the luminous compound on the tens cross to be recharged. When exposed to light, the outsize date mechanism is clearly visible. Thus, the switching action of the date display at midnight can be observed in detail in ambient light.
The DATOGRAPH UP/DOWN “Lumen” is the fourth model of the “Lumen” series that A. Lange & Söhne launched in 2010. A special coating on the semi-transparent sapphire-crystal dial filters out most of the visible light, but not that part of the UV spectrum which is needed to charge the luminous pigments with light energy. The darker the surroundings, the more clearly the displays contrast against the dark background.
