PH3/2 Academy – Louis Poulsen

In 1926, Poul Henningsen had this to say about the new system: "The real innovation of the PH luminaire is that it produces light that is both glare-free and economical. It's quite easy to create glare-free lighting (indirect light or with a thick shade) if some of the light can be wasted. It's also easy to create highly efficient luminaires if you ignore the fact that they are highly irritating to the eyes. But achieving lighting that is both economical and glare-free is an art". 

As early as 1925, Poul Henningsen came up with the idea of using a logarithmic spiral to control the brightness and nuance of luminous light, with each shade equally reducing the amount of light emitted as a function of distance from the bulb. The transitions in brightness between each shade were harmonic, and the relative size of the shades and their positioning were determined by the need to reduce glare, the arrangement of the light and the need for light distribution, according to some remarkably simple principles. The concept was extremely flexible: not only was it possible to achieve different sizes, but also to shape the light with white, silver or gold surfaces. Designer Poul Henningsen imagined that in a restaurant the light should be warm and intimate, and that a golden surface should be used, unlike in a hospital where white surfaces should be used. 

The first luminaires were all made with metal shades, then Poul Henningsen developed a variant in opal glass with a sandblasted lower section. The shades let 12% of the light through and contributed to the ambient lighting of the room, while most of the light was reflected downwards. For the pendant lamps, the sizes of the 3 shades were in a ratio of approximately 3:2:1. For table lamps, the lower shades had to be smaller. This gave rise to the PH 2/1 and PH 3/2 ratios.