A Graphical Presentation of Brightness in the Standard Round Brilliant
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Detail of ISO Brightness as a Function of Pavilion/Crown Angles and Refractive Index for the SRB
This graph presents a relatively high resolution detail of the behavior of ISO brightness over an encompassing range of conventional design angles. 2501 data points are graphed for ISO brightness corresponding to angles from 30° to 50° pavilion mains in .5° increments and 20° to 50° in .5° increments. This data set was systematically calculated for eight different refractive indexes ranging from RI = 1.43 (fluorite) to RI = 2.61 (sphalerite). Use the "Cycle" buttons on this graph to observe the significant effect of varying the refractive index as a variable affecting brightness.

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Bob Keller