Diamond Performance Explained

Diamond Performance – Basics

Learn what makes some diamonds dazzling and others dull.

Note: This page details performance components seen in all diamonds, but the images and analysis tips are specific to round brilliants. Fancy shapes come with many variables and different aesthetic goals.

Positive Diamond Performance

  • Brightness: All reflections of white light (photos below).
  • Contrast: Areas which are temporarily dark due to your head’s shadow (photos below).
  • Fire: Dispersed light your eyes see as spectral colored flashes (photos below).
  • Scintillation: The on-off pattern of brightness, contrast, and colored flashes seen when the diamond, observer or light source are in motion (video coming).

Negative Diamond Performance

  • Leakage: Dark or dead areas where light escapes through the bottom of the stone (photos below).
  • Over-Obstruction: The presence of any observer creates darkness (shallow diamonds)
  • Haze: Clouds, graining or other characteristics dense enough to interfere with transparency.
  • Dirt: (temporary) Dullness caused by grease, dirt or detritus on the diamond’s surface.

PriceScope Pointer: Use our free Holloway Cut Advisor (HCA) tool to reject poor round diamond performance. Request an Ideal Scope image of diamonds you’re considering, to decisively assess brightness, leakage and contrast.

Intermediate Diamond Performance

analysis

Brightness and Leakage

Depending on the main facet angles, light entering a diamond will either reflect and shoot up to the viewer’s eyes (as brightness) or escape through the bottom (as leakage or windowing). In general terms, brightness is desirable, leakage is to be avoided – with exceptions.

diamond brightness and leakage

Store lighting disguises leakage

Stone A is bright in all lighting. Stone B is not. Under normal lighting, areas of leakage cause it to appear smaller and darker than Stone A. Jewelry store spotlights can be used to over-brighten stones, disguising leakage.

diamond performance: brightness and leakage
Acutal Photos (enlarged)

Ideal Scope reveals leakage

Pro tip: An Ideal Scope image will reveal dark or dead areas where light exits through the bottom of the stone. Partial leakage is light pink. Blatant leakage is white.

diamond performance: ideal scope

PriceScope Pointer: Throughout this page we’ll reference Ideal Scope. Click any Ideal Scope link for a fast overview of this simple tool.

Brightness photos by PriceScope members

brightness examples
Thanks to Fancygems, iwanttosparkle, missy, Petalouda, Bonfire, munchee & Emrldlvr

Superior, Average and Poor brightness examples in Ideal Scope

  • Brightness is red.
  • Leakage is white. Partial leakage is light pink.

ideal scope examples

Leakage photos by PriceScope members

leakage examples
Thanks to Laila619, JohnQuixote & TitanCi

See what’s under the hood: If you’re shopping locally Ideal Scope can be used on any round brilliant diamond. Lean more, and consider ordering your own portable Ideal Scope.

intermediate | contrast

Contrast

Some light above the diamond will be blocked (obstructed) by the head of a viewer. This creates a pattern of areas which are temporarily dark.

diamond performance: obstruction
Image courtesy of AGS

Contrast photos by PriceScope members

contrast examples
Thanks to Lucky_Rabbit, Munchee & the_mother_thing

A symmetrical, balanced pattern of contrast helps bright areas appear brighter. This works like a chess board, which has only 1/2 the brightness of a sheet of white paper, but appears brighter by comparison. The brighter the bright areas and the darker the dark areas, the more contrast the diamond has.

When moving, a diamond’s contrast becomes a dramatic component of scintillation.

chessboardpattern

Light from high above usually illuminates the lowest facets on the diamond (the pavilion mains on a round brilliant). When a diamond is being photographed the camera itself blocks light from the highest angles and the lowest facets are darkened, reflecting the black of the camera lens. This creates a contrast pattern which can be useful for assessment.

diamond contrast

Contrast pattern seen in Ideal Scope

Ideal Scope codes light from directly above the diamond black. This simulates the amount of light obstruction caused by the average person’s head at a distance of 25cm (10 inches).

diamond performance: ideal scope

 

examples

Round diamonds cut to have more brightness than fire (Shallow-Ideal and 60-60) typically have narrow pavilion mains, so you will see red than black in the contrast pattern.

ideal scope examples

Round diamonds cut for balanced brightness and fire (Tolkowksky-Ideal and Super-Ideal) typically have a balanced, symmetrical pattern of red and black in the contrast pattern.

ideal scope examples

Round diamonds cut for abundant fire (Steep-Shallow and Antique cuts) typically have wide pavilion mains designed to create larger dispersive-fans, reducing brightness but increasing the potential for a viewer to see fire.

ideal scope examples

Round diamonds produced long ago, or fashioned from oddly shaped rough, may have chaotic, asymmetrical contrast patterns where negative leakage becomes a contrast component.

ideal scope examples

contrast-leakage

Contrast Leakage

Some leakage can create positive contrast effects in a diamond, particularly in fancy shapes, antique diamonds and cuts which don’t prioritize brightness. Contrast-leakage may reveal colors underneath the diamond or gather reflections from the environment, creating an aesthetic unique and specific to each stone.

contrast leakage
Thanks to dreamer_dachsie, yennyfire & Spin-Elle.

advanced | fire

Fire

Dispersion is one of diamond’s most appealing attributes. Visible light is composed of fast wavelengths near infrared to slow wavelengths near ultraviolet. When light enters a diamond those wavelengths start to ‘disperse’ from each other, separating into their component colors.

dispersion

Fire is human perception of dispersion.

If dispersed light arrives to your eye and the dispersive fan is large enough that only one color enters your pupil your brain sees a flash of that color (example A). If the entire dispersive fan is smaller than the size of your pupil your brain recombines all the colors, and your brain sees a flash of white light instead (example B), which counts as brightness rather than fire.

dispersion seen as fire

Learn why you see more colored flashes when your pupils constrict on our Diamond Fire and Dispersion page.

Fire photos by PriceScope members

The camera lens works like your eye’s pupil. If the dispersive fan is large enough that only one color enters the diaphragm the camera captures that spectral color.

diamond fire
Thanks to CHRISTY-DANIELLE & Kaycee2018

Does Ideal Scope show fire?

No. You can draw conclusions about a diamond’s likely dispersion potential based on its proportions, but whether you see a specific diamond’s dispersion as fire depends on your own physiology and the specific lighting environment as much as the diamond’s proportions and cutting details.

Can fire be measured?

Not practically. Dispersion is a physical constant, so it’s possible to estimate a diamond’s dispersive output potential, based on how it was cut. Any measurement of fire is only relevant to the specific environment in which it was measured, at the time it was measured, according to the eyes of whomever did the measuring.

Diamond Cutting and Fire

Diamond experts have known for a long time that high crowns and small tables (like antique diamonds) promote more visible fire because rays of light travel through more diamond material and disperse more. But this combination also produces less light return, therefore less brightness. The reduction in brightness actually makes it easier to see small fire events that might otherwise be overwhelmed by white light return.

Lighting Environments and Fire

A number of small bright light sources overhead will help you see fire in any diamond. You may also see it more readily in a low-lit environment like a restaurant with just a few lights or candles.

PriceScope Pointer: Some people use “dispersion” and “fire” interchangeably but they are not the same thing. Learn how to interpret Diamond Fire and Dispersion here, and perform diamond comparisons like an expert with our In-Person viewing advice.

advanced | scintillation

Scintillation

Scintillation is the on-off pattern of brightness, contrast, and colored flashes seen when the diamond, observer or light source are in motion. It’s the diamond performance combo-platter.

  • On-off Brightness √
  • On-off Fire √
  • On-off Contrast √

Does Ideal Scope show scintillation?

No. You can draw conclusions about likely scintillation intensity based on the diamond’s static brightness and contrast pattern, but scintillation is seen in motion. It will also be different, environment to environment and, as with fire, your specific physiology will determine the amount of on-off colored flashes you see.

Can scintillation be measured?

No. Like fire, any measurement of scintillation is only relevant to the specific environment in which it was measured, at the time it was measured, according to the eyes of whomever did the measuring – and is further confined to the movement choices of that diamond, observer or light source.

lighting

Lighting Environments and Scintillation

Bright spotlights above the diamond promote more intense scintillation, which is why jewelry stores use that scheme. The best store setups have small but powerful LEDs situated above the diamond counter, white ceilings and a single dark colored wall to provide contrast.

Sunlight promotes vivid colored scintillation thanks to your physiology (your pupils constrict and see more fire), but the inside of the diamond may seem dark. This is due to environment. The sun sub-tends light at only about one-half a degree in a 180-degree hemisphere, so it occupies only 1/360 of the total area a diamond “looks” to gather light. So, while you see the (very) vivid sparkles that single (very) bright source creates, the constriction of your pupils makes the surrounding areas effectively dark.

diamonds and sunlight

Filtered sunlight, standing underneath a tree where the leaves permit sunlight to filter down to the diamond, is a great way to enjoy scintillation. Ambient light reaches down to the horizon, promoting edge to edge brightness, while the leaves break up the cascading sunlight, creating abundant scintillation events. Meanwhile, your pupils have constricted (because your brain registers the sunlight) and in that state they clip abundant dispersive fans, causing your optic nerve to perceive far more colored flashes than you do in other illumination scenarios.

PriceScope Pointer: Some people use “dispersion” and “fire” interchangeably but they are not the same thing. Learn how to interpret Diamond Fire and Dispersion here, and perform diamond comparisons like an expert with our In-Person viewing advice.

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