Оценка качества огранки бриллианта...

	Introduction
	Recent achievements
	Building of cut grading system
	Work with scanned diamond models
	Example with tilted table
	BLResponses
	Analysis of illumination
	GIA's illumination model
	"Brill" software analyses light response
	WLR metric and brilliance
	Example with mirrors
	An observer model
	Understanding of brilliance
	Practical value of the cut grading system
	Acknowledgment
	References

Demonstration of adequacy of illumination model no. 3

Photographs of real stones confirm that the illumination model corresponding to Fig.3

is adequate, while the two simplified models (Fig. 1

and Fig.2

) are inadequate:


1. Dark area	2. Blue color	3. Light blue color


4. White area	5. White area	6. White area


7. Yellow color	8. Brown color	9. Dark area

All these pictures are taken on the same conditions with the diamond is rotated with step of one degree around vertical axe. It was illuminated with a big angular size light source. Authors understand that rotating a diamond is not the same as rotating a camera. But there was no possibility to rotate the camera.

To better understand sections 3.3, 3.4, 3.5, and 4, it is recommended to read the following papers published in Gems&Gemology journal:

For section 3.3 - "Modeling the Appearance of the Round Brilliant Cut Diamond: An Analysis of Fire, and More About Brilliance", Gems&Gemology, Fall 2001, Vol. XXXVII, pp. 174-197 (pay attention to the DCLR formula on page 183).

For sections 3.4 & 3.5 - "Modeling the Appearance of the Round Brilliant Cut Diamond: An Analysis of Brilliance", Gems&Gemology, Fall 1998, Vol. XXXIV, No. 3, pp. 158-183.