LED bulbs can make your white shirt ineffective

If you bring your white shirts under an LED bulb to see how white they are, you may not be able make any distinction, a study suggests.

Most LED bulbs produce no violet or ultraviolet light which help whites look "whiter than white".

While some LED bulbs will make colours pop, the vast majority do not showcase or differentiate the appearance of white products, because all white light is not the same.

Whiteners that many companies use to make make whites look "whiter than white", contain fluorescent materials that glow under violet and ultraviolet light.

Sunlight, fluorescent light and incandescent light all produce some light in the violet and ultraviolet range, but most current LED bulbs use blue LEDs to excite a phosphor that then glows white, but produces no violet or ultraviolet light.

When it comes to seeing the colour white, the light source is very important because of how product manufacturers make white products appear white using whiteners, the study noted.

"Retailers have long been concerned with the colour-rendering qualities of their lighting, but less aware how light sources render white," said Kevin W. Houser, a professor of architectural engineering at Pennsylvania State University.

The study involved 39 participants to observe various combinations of light sources and white objects to see how the light source affected perceptions of white.

"The light sources with higher violet component permitted the best discrimination between the targets," said Houser.

For an accurate rendering of whiteness, engineering of an LED source's spectrum is necessary, concluded the study.

The study appeared in the journal Leukos, the journal of the Illuminating Engineering Society.