There is a tendency among diamond buyers to try and buy diamonds by the numbers, with the assumption that diamonds with an overall cut grade of GIA Excellent or AGS Ideal will deliver the best visual performance. However hidden factors of diamond cut quality, such as contrast brilliance can make or break a diamond in terms of our perception of sparkle. The 1.708 carat, E-color, VS-1 clarity, Brian Gavin Signature round diamond featured to the left, exhibits a high level of contrast due to the overall diamond cut quality, and as a result it will look fantastic in practically all lighting environments!
Why is Contrast Important in Diamonds?
A high degree of contrast is critical to diamond visual performance because it creates a visual separation between the light and dark areas of a diamond, which our eyes perceive as depth and sparkle.
In terms of actual sparkle, most people are familiar with brilliance which is white sparkle, and dispersion or “fire” which is colored sparkle. There is also scintillation, which is the sparkle created by the difference in contrast between the light and dark sections of a diamond when the diamond is in motion… this is also known as dynamic contrast and it is improved dramatically by higher levels of optical symmetry, which is the precision of facet shape and alignment.
Another type of contrast is the static contrast which is created by the visible difference between the light and dark areas of a diamond, while the diamond is sitting still. The static contrast of a diamond can be judged by looking at the degree of contrast exhibited between the arrows pattern and the lighter sections of the diamond in clarity photographs like the one provided for this 1.708 carat, E-color, VS-1 clarity, Brian Gavin Signature round diamond, which POPS off the page even though it’s not moving! By the way, the arrows pattern is dark because of the shadow created by our heads blocking light from reflecting off of the pavilion main facets which are located on the underside of the diamond.
The effect that the diamond is sparkling when in fact it is not moving is known as contrast brilliance, and it is the direct result of proper proportions combined with exceptional levels of optical symmetry. Subtle differences in the offset for the crown and pavilion angles of a diamond, combined with variations of lower girdle halves measurements and star facet length, as well as any variation in the indexing of the facets, will have a dramatic effect upon the degree of contrast exhibited by a diamond.
For instance take a look at the wide range of contrast exhibited by these round brilliant cut diamonds which were produced by my search for diamonds on James Allen, using my preferred selection criteria for polish, symmetry, table diameter, and total depth, with all of the diamonds having an overall cut grade of either AGS Ideal-0 or GIA Excellent.
The primary difference between these diamonds are the crown and pavilion angle measurements, combined with different levels of optical symmetry, and different lower girdle halves and star facet measurements. The degree of contrast between these diamonds and the 1.708 carat, E-color, VS-1 clarity, Brian Gavin Signature round diamond referenced at the top of this page is clearly visible.
It should be noted that James Allen does offer diamonds which exhibit high levels of contrast, it just takes a little more effort to find them because they offer a wider range of diamond cut quality than Brian Gavin who specializes in the production of super ideal cut diamonds which exhibit high levels of contrast and he doesn’t inventory anything else. Let me know if you’d like help finding a diamond which meets my selection criteria with regards to proportions and overall cut quality.
One of the things which I appreciate about dealers like Brian Gavin and James Allen is that they provide the images necessary to judge contrast brilliance on their diamond details pages… Once you know what to look for, it’s easy to flip through the clarity photographs and eliminate the options which exhibit low levels of contrast, or which show signs of uneven distribution of light, tips of arrows that fade out, missing arrow shafts, etc.
Another dealer who provides the images of a diamond that are necessary to judge diamond cut quality and contrast brilliance is Wink from High Performance Diamonds. Unfortunately the vast majority of diamond dealers online do not provide this type of detail, perhaps because they don’t have the diamonds in-stock and therefore have absolutely no clue about the visual properties of the diamonds which they advertise for sale… And they are certainly not capable of providing us with the reflector scope images that we need to complete the remainder of the diamond evaluation puzzle! But that’s the subject of a different blog post…