||In the late 1970's before the advent of low wattage metal halide lamps, it was still desirable to use mercury discharge light sources indoors for general illumination. However, even the modern Yttrium Vanadate and Yttrium Borate coated lamps still cast a rather cold light though with a fairly high colour temperature.
Osram therefore introduced a line of mercury lamps which combine the phosphor with a gold-coloured filter applied to the inside of the glass bulb. The action of the fluorescent phosphor is unchanged, but the coating served to filter out a proportion of the blue mercury radiation thus making the relative red light contribution of the phosphor greater than in standard lamps. Of course, the effect was also to greatly reduce the luminous efficacy of these light sources, but still they performed better than incandescent products and offered a considerable advantage in useful life time.
The so-called Gold Super Deluxe lamps are still standard production items today, although demand is of course reducing as compact metal halide sources become more popular. They are offered only in low wattages of 50, 80 and 125W for typical indoor applications, and are made in three different formats - the plain elliptical bulb shape, a reflector style, and this large diameter spherical globe. This latter version is particularly popular in applications where the lamp itself is on view, as its large surface area presents a low surface luminosity and minimises glare. Today the Super Deluxe HQL-B lamp is employed in applications such as ornate glass lanterns in city centres, where a warm good quality incandescent-like light is desired but with moderate luminous efficacy and without giving rise to serious glare.