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Now Playing: eCS = 1.00 = Ideal Cut Diamond (the most sparkle)
eCS = 1.00 = Ideal Cut Diamond (the most sparkle)
it is possible to put a number value on the Sparkle of a diamond


a truely easy to read numerial designation for a diamonds sprarkle
Posted at 4:46 PM, Nov. 24, 2005


www.e-Praise.com



The New e-Praise Cut Score (eCS) and the
Importance of Cut Proportions


The human eye is exquisitely sensitive to slight differences between two diamonds, but only in direct comparisons. Viewed separately, many diamonds, especially those toward the high ends of the three "C" scales of Color, Clarity and Carats, look alike to most observers. Any diamond with Color between D "Colorless" and H "Near Colorless" appears colorless, unless it is placed next to another, much lighter comparison stone. Diamonds in Clarity grades between F "Flawless" and VS2 "Very Slightly Included" have no obvious visible flaws unless viewed by an expert under 10x loupe magnification. A diamond of 0.9 Carats weight is obviously smaller when seen right next to a 1.1-carat stone, but viewed separately, few people could distinguish them. But it is the fourth "C", its Cut, that can make a diamond stand out as a "sparkler" that even an amateur viewer immediately appreciates. Well-proportioned diamonds reflect and refract light such that they seem to float slightly above a supporting surface and to almost glow of their own power. This characteristic overcomes even rather severe shortcomings in other "Cut" features such as polish or symmetry.

Although of all the "4 C's", the craftsmanship features that comprise a diamond's Cut have the most profound effect on the overall beauty of a diamond, current descriptions of this measure of quality are the least satisfactory. The prominent gemological laboratories including AGS and GIA have devised several extremely complex cut grading systems that they promise to include in future quality reports. These will make rational and well-accepted conceptual frameworks for professional diamond dealers and appraisers, but may not be directly helpful to the retail customer in selecting the best diamond for the price.

There are images on our site that illustrate the simplest example of how the path of a single light ray entering the top table facet is redirected by internal reflections in differently crafted diamonds. If the cut proportions are either too shallow or too deep, a large portion of incoming light "leaks" from the bottom pavilion facets, reducing the amount returned to the viewer. Exactly which combination of cutting angles should be deemed to be in the "ideal range" has been debated since Marcel Tolkowsky's landmark analysis published in 1919. At e-Praise, we have developed a much simplified approach that uses the diamond's reported scalar measurements to compute an e-Praise Cut Score (eCS). The eCS places a diamond's geometric proportions on a fractional scale. If the diamond's most important proportions are within the ranges widely accepted as providing the most brilliance in each of the popular diamond shapes, its eCS is equal to 1.000. A lesser score, such as 0.992, indicates that the diamond's proportions are less "ideal", and the gem is expected to have less sparkle because it was cut too shallow or too deep.

Our appraisal formula applies value adjustments for each of the features of shape, finish, polish, culet size, girdle thickness and so forth that are recorded in the laboratory quality report. These relative value corrections are well established in professional appraisal practice. We treat the geometric proportions separately. The diamond is analyzed to determine if further changing one of its more important dimensions could have improved its "brilliance". If so, its value is recalculated based on this theoretical adjustment and only then is evaluated for its other features. The amount of any necessary modification is reflected as an eCS less than 1.000. The meaning of a diamond's eCS is simple to interpret. For example, a score of 0.990 indicates that as little as a 1.0% alteration of a diamond's proportions could have brought out its very best brilliance and fire. A small improvement in proportions potentially adds dramatically more beauty and value than is lost by a small reduction in carat weight. Using our "expert system", our monetary value results closely parallel the seemingly "subjective" opinion of expert appraisers with many years of experience comparing diamonds.

This is not to mean that we generally recommend the actual re-cutting of a low-scoring diamond, but that we encourage buyers to choose only gems as close to eCS=1.000 as will fit in their budget. This makes selecting the "most for your money" a relatively simple task. eCS's should be known to anyone planning to buy a diamond, but are generally unavailable. As a valuable resource for comparison shopping, we offer our inexpensive Online Retail Value Estimator, which reports the same eCS as is used in our full certificates.