The light performance grading system calculates values for each diamond to provide an overall score. The stones are graded based on the overall strength of light performance, along with sub-component scores for brightness, fire, and contrast.
‘Brightness’ refers to reflected and refracted white light, while ‘fire’ is flashes of colour. ‘Contrast’ is defined as the balance and intensity of the light and dark areas, while ‘light performance’ is an assessment of all three factors in conjunction with one another.
In a statement, IGI CEO Tehmasp Printer said this report was introduced due to increasing industry demand.
“In recent years, we have seen increasing interest in expanded performance analysis,” he said.
“IGI has responded by creating an easy-to-understand, science-based light performance report along with cutting guidelines for diamond producers, empowering them to target the best results.”
Two decades in the making
The scores are evaluated using an instrument known as an ‘Ideal-Scope’, invented by Australian jeweller Garry Holloway.
It is a simple bright-coloured reflector with a viewing hole and lens, creating a structured light environment. The concept was first developed in Japan in the 1970s. Holloway’s Ideal-Scope is a next-generation portable variant.
Holloway has been in discussions with IGI on various topics for more than 20 years and was pleased to see the institute’s gemologists and educators implementing his approach to light performance grading.
“Other reports favour deeper proportions than those which I believe are optimum. This has come about because people are always looking closely at diamonds for clarity and inclusions,” he told Jeweller.
“It’s rare to look at a stone from closer than 40 centimetres when people show off diamond jewellery. For example, looking at a woman’s engagement ring, you see it at arm's length.”
Holloway explains that 50-60 per cent of diamonds (in dollar value) are set in rings. The rest are set in earrings, pendants, and bracelets, typically viewed from an even further distance.
“Everything I’ve done concerning grading has been based on that longer focal distance. It makes sense to me that shallower proportions are more favourable when the viewing distance is accounted for.
“I’ve been saying this for a very long time, more than 25 years, and I think it’s great that the IGI has decided this is a very effective way to grade diamonds.”
The majority of IGI’s operations are based in India. It specialises in grading finished jewellery and lab-created diamonds.
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