Optical Cut Analysis - Lightscope
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We desire well cut diamonds because of their desirable light return. So, wouldn't the best way to judge the cut quality be to observe it reacts to light?
Unfortunately, the lighting in most jewellery stores are unnaturally bright spotlights. Some people cover the diamonds with their hands or look at them under at table, but that does not work because we are trying to determine the diamond's reaction to various light sources. So, we cannot judge its beauty in the absence of light.
In addition, as a layman, it is very difficult to judge the cut quality just by looking at the diamond alone. That is where a LightScope would come in useful because light return and light leakage are quite obvious under the lightscope, even to a layman.
What is a Lightscope?
A LightScope is a simple device for viewing the light return of a diamond.
Different makers of LightScopes call their devices by different names. IdealScopes, FiresSopes and ImageScopes are all essentially the same thing. Of course, some are made better than others, but they perform the same function.
For the purpose of photography, the quality of the lightscope is very important since it has to work well with the digital camera and macro lenses, etc. However, for laymen, a simple IdealScope will suffice.
How does it work?
The facets of a diamond function either as a reflective mirror, or a leaky window. Therefore, we have to differentiate the two.
If we are able to tell if the origin of light is from the top or the bottom of the diamond, we will then be able to know if the facets are working as mirrors or windows.
To do that, we place a red cup with a viewing hole over the diamond. Then we place a white light source at the bottom of the diamond.
Whites: So, when we view the diamond, and see white, it means that the light is from the bottom of the diamond. This indicates that the particular facet showing white is not reflecting much light from the top. It is an indication of blatant leakage.
Blacks: If we see black or dark grey, this means that the source of light is directly from the top. Since we have a viewing hole on the red cup. Light coming directly from this hole appears black because it is the reflection from your eye.
Reds: If we see red, or dark pink, this means that the light is coming from the top, but at an angle. Light that has reflected off the surface of the red cup and onto the diamond will look red. Facets showing red or dark pink are reflecting a lot of light.
The lightscope depends on the reflection off the red cup to work. That is why the technology is sometimes called 'reflector technology'.
If you have read the earlier section on Brightness and Contrast, you would have learned that a diamond's contrast is created by having a good combination of light coming from different angles. Since the lightscope shows light coming directly from the top as black, at an angle as red and from the bottom as white, we can evaluate the diamond quite easily.
Star and Hotspots
Next, Let us take a look at a few more Lightscope images to learn what we can tell from looking at them.