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Why do diamonds go dark?

bluelotus

Shiny_Rock
Joined
Feb 20, 2013
Messages
257
I have sometimes noticed that my diamond goes dark in direct sunlight. Is this just an optical illusion? I guess not if I am able to photograph it?

_2171.jpeg
 

Tourmaline

Brilliant_Rock
Premium
Joined
Nov 17, 2013
Messages
1,795
This can be a combination of cut and clarity. I think my diamond is very similar to yours (we have established that previously). Mine does this, too, in the head-on view. I have mine set in an open prong setting, so if I turn it to a slight angle away from head-on, it lights up again. :)
 

John Pollard

Ideal_Rock
Trade
Joined
May 1, 2008
Messages
3,555
bluelotus|1456494403|3995982 said:
I have sometimes noticed that my diamond goes dark in direct sunlight. Is this just an optical illusion? I guess not if I am able to photograph it?
Good observation. There are two primary reasons:

1. The sun only sub-tends light at about one-half a degree. This means, in the entire 180-degree hemisphere, the sun is one tiny point light source occupying 1/360th of the area a diamond is trying to "look" for light. So while you see the (very) bright sparkles such a small bright light source creates, confinement to only a half-degree limits what the diamond finds to give-back.

2. Human physiology. Your pupils get smaller in sunlight, further reducing brightness in the fore-and-background. The positive is that well-cut diamonds explode with more colored-sparkle... Why? Because when your pupils are smaller they are 'clipping' more dispersive fans so you're seeing more of them as color, rather than recombined white light.

Adaptation photo in this thread: https://www.pricescope.com/communit...monds-revisited.150108/#post-2720418#p2720418
Pupil-clip graphic in this thread: https://www.pricescope.com/communit...re-in-dim-light.122718/#post-2144269#p2144269
 

Michael_E

Brilliant_Rock
Trade
Joined
Nov 19, 2003
Messages
1,290
In your picture the light from the sun is not entering the stone through the table, but glancing off the stone from the side. If you really must take a picture in the sun, put the sun at your back and hold your stone up so that the sun can enter through the front of the stone. You camera will probably still shade the stone too much, but it's better than how you're trying it now. One of the best ways to get a really good display, at least this time of year, is to stand under a leafless tree on a bright overcast day. The bright light from the sky and the dark reflection from the tree limbs makes a great contrast and also shows fire, (dispersion), nearly as well as being in a jewelry store.
 
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