Ideal Scope – Diamond Cut Quality Tool

In the 1970s a Japanese scientist named Okuda developed ways to study diamond light performance using colored reflectors in magnified scopes. This method of diamond assessment became popular on the internet with Garry Holloway’s “Ideal-Scope”, a simple magnifying tube containing a red reflector. The ideal scope creates a structured light environment. When the diamond’s girdle is aligned with the bottom of the tube, light entering the crown from above and properly returning to the eye will appear red. Light escaping or ‘leaking’ out of the diamond's pavilion appears white. Light that comes from the very highest angle will appear black and represents light that is obscured by the observer’s head.

Interpretation of ideal scope images is simple. Here are sample photos of well-cut, average and poorly cut diamonds.

• Black areas indicate light returned at very high angles. These areas are dark in the ideal-scope because light from directly above is blocked by the camera.
• Red areas indicate the brightest light returning to the eye.
• Pink areas indicate less intense light return.
• White or grayish areas indicate light escaping, or ‘leaking’ out of the diamond’s pavilion and not being returned to the eye.

The finest cut diamonds have an abundance of red, a minimum of white/gray, and a pattern of symmetrical black arrows radiating from the center. Average cut diamonds have areas of pink, gray and white leakage. Poorly cut diamonds have large areas of leakage and chaotic patterns.

An ideal scope photo also gives an idea of the diamond’s proportions and symmetry. High levels of optical symmetry results in a sharp pattern of arrows in the crown. Good proportions result in robust light return.

You will notice a small regular pattern of small white leakage around the perimeter of well-cut diamonds. This type of leakage is acceptable and contributes to positive contrast and scintillation.

While there are DYI methods of taking diamond photos with digital cameras including the camera in a smart phone, all diamonds in our inventory are photographed using a specially designed standardized capture system. This system utilizes a transparent Lucite tray in a controlled studio with daylight equivalent backlighting source as illustrated below. For more info see our page on Whiteflash Diamond Imaging.

Reflectors are the oldest and simplest method for reliable, uniform assessment of light performance in a diamond. AGS Laboratories uses a similar device for light performance assessment in its cut-grading system called the ASET or Angular Spectrum Evaluation Tool. The ASET provides additional detail about how the diamond is handling light. In addition to being an easy to use reflector tool, the ASET framework is integrated into the AGS computerized light performance grading system.