Sydney: You are probably right if you suspect that your new compact fluorescent lamp (CFL) is not as bright as the old bulb that it replaced.
Most new CFLs fail to live up to manufacturers` claims that they emit as much light as a 75-watt incandescent lamp, as tests by a team of University of New South Wales (UNSW) optics researchers have shown.
Most performed poorly regardless of retail price. Only one in four meets the minimum standard required in other countries to justify a claim of equivalence to an incandescent wattage for light emission.
The problem is not so much in the CFLs themselves but in the labelling that rates their equivalence, says Stephen Dain, UNSW professor and study author.
"We found that in two-thirds of cases a CFL that is claimed to be the equivalent of a 75-watt incandescent lamp delivers a lot less light than you expected. Some are only the equivalent of an old 60-watt lamp," says Dain.
"The public seems to be disappointed when they replace an incandescent lamp with a CFL claimed to be equivalent. This study shows that they are really not as good as they are made out to be," adds Dain.
Globe and spiral-shaped CFLs distributed light more evenly - much like incandescent lamps - making them the best choice for unshaded light fittings, says an UNSW release.
Double, triple and quadruple biaxial CFL lamps tended to throw light sideways, with very little being directed downwards.
The study was published in Clinical and Experimental Optometry.