||Despite the phenomenal success of the MR16 display lamp for professional display lighting, its requirement for a low voltage transformer was an obstacle to its penetration into domestic and semi-professional applications. PAR and R lamps continued to hold court for many years, but were losing popularity on account of their large dimensions and the lack of sparkle from their optical surfaces. With groundbreaking fashion, Sylvania invented a major new format in 1996 to offer the best of both worlds. Dubbed ES50 (= Extra Short 50mm) it offers the size and aesthetic appeal of the sparkling MR16, while operating directly from the mains supply without the need for any transformer.
It was made possible thanks to the miniature W-shaped filament, in which a 230-240V coil measuring some 25mm long is folded into a tiny halogen capsule small enough to be focussed in the 50mm reflector. The capsule is made from aluminosilicate hard glass instead of the usual quartz, this permitting the glass-to-metal seals to be made with molybdenum wires instead of the usual flat foils. There is space to seal five wires through the seal and this is a requirement to mount the W-shape filament. A parallel invention was the GU10 base, having a positive twist-and-lock action - a major improvement over the fragile 12V pins.
GU10 lamps have since grown to a position of dominance in retail markets, despite being less efficient than the low volt MR16. Whereas 12V 50W lamps operate at about 20lm/W the first 50W GU10 capsules achieved only 10.5lm/W. On top of this the larger filament results in inferior beam control. Hence a 230V lamp typically delivers a beam intensity 3 times less than an equivalent 12V lamp.