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my diamond seems to sparkle more in dim light...

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iloveny

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why is that? It''s and emerald cut, and I thought that emeralds weren''t supposed to be very sparkly. I''ve never worn a round brilliant center stone, but there are some in my setting. My center stone seems to sparkle just as much as the rounds, and I see more rainbow sparkles in dim lighting. It really sparkles well in bright lighting as well, but why does it look even better in dim lighting?
 

Lorelei

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It could be showing more fire/ coloured light in dimmer lighting and that is what you are noticing at a guess.
 

Garry H (Cut Nut)

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Date: 8/13/2009 5:59:07 AM
Author: Lorelei
It could be showing more fire/ coloured light in dimmer lighting and that is what you are noticing at a guess.
yes
in bright lights it probably is a case of the bright flashes drowning out the firey ones
 

John P

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Date: 8/12/2009 8:00:46 PM
Author:iloveny
It really sparkles well in bright lighting as well, but why does it look even better in dim lighting?
What you see can also have to do with your personal physiology.

Diamonds disperse light into their spectral colors (like a prism). If a ray of dispersed light reaches the pupil of your eye and that ray is wider than your pupil you see a flash of color if your pupil "clips" it before it recombines. But if your pupil is wider than the ray you perceive all the colors at once and see it as white light. So in dim light, when the pupils are more dilated/open, there is a greater chance to see white light and less chance to see color. Your may see more scintillation but you'll typically see less dispersion/colored flashes.

As it gets darker another factor comes into play. Your retina has two kinds of light sensitive cells; cones and rods. Cones perceive color but they don't work in darkness. So when it gets dark, in addition to dilated/open pupils, you're also seeing with rods and rods don't perceive color (thanks to jstarfireb, who first brought this up on PS).

Your step-cut is likely cut in a way that creates large virtual facets. Larger VFs logically create rays you are more likely to perceive as color - often the charm of antique cuts such as OEC and OMC which create large VFs (more on virtual facets here). People are different and it's also possible that your eyes dilate less than others', in which case you enjoy more color in low light conditions as a part of "who you are."

So for anyone who wonders why you see crazy color in bright situations like a jewelry store showroom that's why: Your pupils "clip" more of the dispersed rays before they recombine. Studies like the one linked above are explaining why diamonds with high levels of optical symmetry often create more visible colored flashes in low-light conditions; optical symmetry results in larger VFs. Many vets will remember that the Eightstar diamond company made a name for themselves 20 years ago with rounds that showed colorful sparkle in low-light conditions. It's easy to understand why; their recipe of optical symmetry, short lower halves and painted upper girdles all worked toward creating larger virtual facets. Coupled with human physiology their approach was a great way to acquire a different signature "look" than other RBs of the time.
 

John P

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Date: 8/13/2009 11:44:55 AM
Author: strmrdr
Easy to understand article on VF's is here:
http://journal.pricescope.com/Articles/61/1/Virtual-Facets-and-patterns%2c-a-Discussion-about-step-cuts-.aspx
That's right. Great reference, especially for this thread dealing with EC.


I found the prior thread I was reminded of. Here are some graphics:

- We all know how dispersion works.

dispersion-prism-coolpinkfloyd.jpg


- If your pupils are wide open that dispersed light has a better chance of recombining by the time it hits the retina, and when we see all the colors of the spectrum we perceive it as white light (modified NYSOA graphics below).

pupil-dilated-dispersion.jpg



- If you pupils are undilated (closed) there is a better chance the dispersion will get "clipped" before it hits the retina, and you will perceive color - the graphic is not technically precise but I hope it serves the purpose.

pupil-undilated-dispersion.jpg
 

LGK

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So, if a person were to, say, take opiates (which constrict pupils quite a bit in any light) their diamond would appear to have more fire? Next time I dislocate my knee I''m totally testing it!
 

iloveny

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wow John- thanks for the detailed scientific response! Pretty cool stuff.
 

Rhino

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Date: 8/13/2009 2:02:31 PM
Author: LittleGreyKitten
So, if a person were to, say, take opiates (which constrict pupils quite a bit in any light) their diamond would appear to have more fire? Next time I dislocate my knee I''m totally testing it!
LOL
 

amyjokerette

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Thank you John P. for the detailed explanation!! That makes total sense and it puts into words what I have seen with my eyes
1.gif
 

strmrdr

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A well cut EC has a lot of sparkle, why they have a reputation for being dead is so few of them are well cut.
The classic EC is pretty dead. Huge table and flat crown.
 

cheradrian

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Interesting discussion, thanks John for posting the detailed/technical info.

Question - how does this work with videos of diamonds? I suspect that the same effect does not take place with the eye when watching a video - true or false?
 

HopeDream

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Hi,

Iloveny your ring is gorgeous!

I'd like to riff on the optics section of this thread.

Do larger facets disperse light more widely than smaller facets?

(Would larger facets be more likely to display fire than smaller facets ?)

eg. two diamonds with exactly the same angles and proportions, but one is twice the size of the other?


I have a ring set with tiny diamonds and all I seem to get is white light return, so I'm wondering if diamond size is a factor.

I love learning more about the technical aspects of light performance.

Thanks

HD
 

Serg

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see " Fig. 2. The saturation of observed color and its dominant wavelength l in dependence at various selected wavelength intervals Dl.





"
from Rainbow from a colorless gem. by A.V. Vasiliev 1995year





Actually, the ray begins to disperse upon entering the prism, but this is much less than at exit. Because the prism size is negligible compared to its distance from the eye, we will neglect the input dispersion. Should all this ''fan'' enter the pupil of the eye, the eye''s lens will focus all of it into a white-colored dot on the retina.

However, if the fan area exceeds pupil size at the eye location, then only a part of the ''fan'' cut-off with the pupil would be focused on the retina.

The distance from the gem to the observer can vary, so instead of linear pupil size it is more convenient to employ its angular size, i.e. the angle at which the pupil diameter is seen from the gem. If the angular ''fan'' size exceeds the angular pupil diameter, then only a part of complete visible spectrum radiation of certain wavelengths will hit the focused dot on the retina.

The higher the prism angular dispersion and the narrower the pupil, the narrower would be the wavelength band Dl cut off from the complete spectrum, resulting in higher saturation of the colors observed.
 

Serg

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The saturation of observed color and its dominant wavelength l in dependence at various selected wavelength intervals Dl.

saturationVasiliev.jpg
 

Serg

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Date: 8/12/2009 8:00:46 PM
Author:iloveny
why is that? It''s and emerald cut, and I thought that emeralds weren''t supposed to be very sparkly. I''ve never worn a round brilliant center stone, but there are some in my setting. My center stone seems to sparkle just as much as the rounds, and I see more rainbow sparkles in dim lighting. It really sparkles well in bright lighting as well, but why does it look even better in dim lighting?

Any cut has more Fire in light with small ( angular size) light sources
Dim lighting usually has small size light sources
Big light sources are Fire killers
 
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