Diamond Viewing - Is Brighter Better?

Lighting can affect perception. And when we are buying, selling, sorting and grading diamonds it is especially important to preserve the integrity of diamond grading. The results have to be consistent and repeatable, with both buyer and seller viewing a diamond in equivalent lighting conditions. If a diamond is graded at GIA®, Stuller and your store, the results should be the same.

Not All Artificial Lighting Is Equal

Each type of lighting technology has its own emissions and wavelengths, which produce different results with diamonds.

More bulbs in a lamp does not necessarily mean better lighting. if it is too strong, it may oversaturate the stone washing out its true color. Lighting with too much UV emission causes subtle color changes when it reacts with the nitrogen in the diamond and makes a slightly yellowish diamond appearing slightly bluish. This translates to different grades, different pricing and different profits. When we adhere to the accepted standards, we ensure consistency in grading.

Industry Standards For Lighting

According to GIA, the current standards for lighting used for diamond grading are the following:
  • Stable, fluorescent lamps 17 inches or longer
  • Intensity of light in the range of 2000-4500 lux at the surface of the grading tray
  • The distance between the lamps and the grading tray should be between 8 and 10 inches
  • Color spectrum close to CIE D55-D65
  • A color temperature between 5500 K and 6500 K
  • Color rendering index of 90 or above
  • A high-frequency (>20,000 Hz) electronic ballast
  • Light ballast with efficiency (power factor) above 0.5 (50%)
  • No noticeable output in the short or medium wave UV range
  • Emission for long-wave UV (between 315 and 400 nm, close to the reference spectrum of D55-D65)