Every time light enters a diamond it does not always result in seeing this phenomena of fire or dispersion.  This graphic which we've referenced in our chapters on contrast & brightness certainly does not depict fire but brightness in hemisphere lighting because of reflector contrast (reflecting back darks and lights with minimal leakage contrast).

If we take a similar diamond into a completely different lighting environment, particularly strong light sources (commonly referred to as direct lighting conditions) like halogen's, LED pin type lighting, direct sunlight, spotlights, etc. we will then be observing a completely different appearance which flatters the metrics of fire and dispersion.

Here is a graphic depicting this metric in a similar looking stone to the one above.  Look how different the diamond changes in appearance.

In the above illustration you can clearly see colored light coming out from within the diamond. Yellows, greens, blues, pinks, & orangey dispersion coming from within.

Why?  A general rule of thumb with diamonds is the stronger the lighting conditions the more the diamond should be functioning in its role as a prism. The sun, being one of the strongest light sources possible will produce strong flares of dispersion as it hits a well cut diamond (as in the first photograph).  While strong fire is a highly desirable optical feature to observe in diamonds the rest of the diamond, which is not reflecting back those flares will generally appear very dark or even silvery looking. Many people, when viewing their diamond for the first time in direct light conditions often become concerned because of the darkness that appears and oftentimes confuse this as being inferior in color when that in fact is not the case.  Even a "D" colored diamond will appear dark in direct lighting.  In a well cut stone however ... get your sunglasses ready because amidst the darker facets will appear beautiful flashes of colored light.

In bright ambient light (such as natural daylight and you may be standing under a tree or in an office with a window allowing natural ambient daylight in) it is very possible to see a soft dispersion playing amongst the facets with a nice mix of white light akin to the model on the left in the illustration below. Note the soft dispersion of colors coming out of the diamond with a nice observance of white light return as well.

The graphic to the right more accurately depicts (though not exactly) the lighting condition in the photograph above it as the lighting is strong enough to produce strong dispersion.  So the strength of fire observed within diamond depends primarily upon 2 factors.

• The ability of the facets to function as reflectors and

• The strength of the light source in which the diamond is being observed under.

Let's take a look at a stone with the "ring of death" (steep/deep angle combinations) under the table for a comparison alongside these.

Note that in the static images the darkness under the table caused by the leakage in the last stone.  Also note the absence of dispersion in the static image under strong ambient lighting in the first stone.

One last comparison for fire/dispersion would be a shallow/shallow combo (opposite of steep/deep).

That last shallow/shallow combo gets an AGS "2" cut grade for performance and a GIA Very Good (their 2nd grade). The steep/deep used  in this example is the GIA Excellent we used in our Leakage chapter. What does this tell us? Again, GIA is relying more heavily on the contrast brightness/fire/scintillation appearance in the office lighting view than they are direct lighting as in this illustration.  This emphasizes the need for *assessing the diamonds visually* as the first 2 stones used in this illustration are both GIA Ideals.

If you take careful note in the graphics above, the shallow/shallow has fire/dispersion on par with the Ideal in the first column.  What does this teach us?  If this lighting  condition is most important to you in your purchasing decision you could get a nice fiery stone with strong dispersion for a cheaper price.  However the cheaper price will also dictate perhaps a not so pleasant appearance in other lighting conditions.  Our goal here is balanced visual's in all lighting environments which is what we generally purchase, however we will be introducing new ideals that we traditionally did not purchase in the past in an effort to better serve our clients based on their own personal preferences.

The Type of Contrast Observed in Direct Light Conditions

In hemisphere lighting we can easily see the results of what I will refer to as "reflector contrast"; contrast as taught by AGS and viewed through ASET.  In office lighting leakage contrast becomes another important factor in the optics and appearance of a diamond which GIA takes into account as well as the above in their final grade.  In direct light conditions the contrast observed is that between darker areas of the diamond as compared to areas reflecting back more intense reflections.  It is still a contrast of darks and lights but now tables have turned in a sense which is best demonstrated in these photographs.

Note in the dispersion graphic that the areas of the diamond that are not reflecting back light appear to be very dark.  This is true in real world observance as well.  So we see then that contrast can take on many different forms depending on the environment in which the diamond is viewed in.  What is most important to you, of course is what counts most.