What are the Ideal-scope and ASET?
In the 1970s a Japanese scientist named Okuda developed ways to study light performance using colored reflectors in magnified scopes. This method of assessment became popular on the internet with the “ideal-scope,” a simple magnifying tube containing a red reflector that creates a structured light environment. The Ideal-Scope was developed by Garry Holloway FGAA, DipDT, JAA Appraiser. An ideal-scope photograph shows what areas of a diamond return light to the viewer’s eye and what areas do not. In 2005 the AGS introduced a similar scope, the Angular Spectrum Evaluation Tool. Based on the same principal, the ASET shows light return using multiple colors. The AGS grades light performance as part of cut on a scale of 0 through 10. Diamonds earning the top grade of 0 are considered “Ideal.” Only a fraction of the world’s diamonds will earn this grade. In these scopes, light returning at extremely high angles will be dark since that light normally comes from directly above and is blocked by
