Setting, covered or open?

[haflc]

I've read a few posts that state a dirty pavilion will decrease the look and performance of a stone.

1. If most of the light is reflected from the inside of the stone, how does the outside have any effect?

2. If outside factors do truly play a role, does the type of setting effect the stones performance also (open vs closed)?

Thanks for your help.

 

[yssie]

Think about it, why does a diamond return light in the first place?

RI oil = 1.5ish.

 

[yssie]

w/ refractive index = c/v, v speed of light through a substance

RI air = 1, RI diamond = 2.41 (say RI oil = 1.5)

we know critical angle = sin^(-1)[RI1/RI2], RI1 less dense media, RI2 more dense, and we know crit angle only real if RI1/RI2<1 (as in, t.int.refl not going to happen when light travelling through air is incident on water/glass/diamond...)

so crit angle for light traveling through diamond to air at boundary = arcsin(1/2.41)=0.43rad
for diamond to grease boundary arcsin(1.5/2.41)=0.67rad
since critical angle is larger when you have grease lining the outside of a diamond light must approach that boundary from a more severe angle to be internally reflected (not lost through the pavilion)


pic - clean diamond, light can strike pav at any of the angles in grey and you get tot int refl, with a dirty diamond (orange dirt) grey area is a much smaller range


ETA: radians*. deg = rad*180/pi

 

[haflc]

I was also able to find this bit of info.

Under "ordinary conditions" it is true that the creation of an evanescent wave does not affect the conservation of energy, i.e. the evanescent wave transmits zero net energy. However, if a third medium with a higher refractive index than the second medium is placed within less than several wavelengths distance from the interface between the first medium and the second medium, the evanescent wave will be different from the one under "ordinary conditions" and it will pass energy across the second into the third medium.

It makes sense now.

 

[kenny]

Yes a dirty ideal-cut diamond can no longer perform as an ideal cut diamond.
Dirt not only reduce the light, it causes it to be sent in the wrong direction.

Be like Kenny - clean your diamond constantly.

There has even been discussions here of what proportions would perform better when diamonds are dirty.

 

[yssie]

I was also able to find this bit of info.

Under "ordinary conditions" it is true that the creation of an evanescent wave does not affect the conservation of energy, i.e. the evanescent wave transmits zero net energy. However, if a third medium with a higher refractive index than the second medium is placed within less than several wavelengths distance from the interface between the first medium and the second medium, the evanescent wave will be different from the one under "ordinary conditions" and it will pass energy across the second into the third medium.

It makes sense now.

electric field disturbance in air at site of tIR decays exponentially w/ distance - it is not a propagating sinusoid, and it doesn't matter anyway because the tiniest proximal particles in the air would scatter the "evanescent field" energy


ETA: what they are talking about is if you have a second piece of whatever substance through which tIR is also occuring and you put them so close together that the evanescent fields overlap you can get actual power exchange

 

[haflc]

I was also able to find this bit of info.

Under "ordinary conditions" it is true that the creation of an evanescent wave does not affect the conservation of energy, i.e. the evanescent wave transmits zero net energy. However, if a third medium with a higher refractive index than the second medium is placed within less than several wavelengths distance from the interface between the first medium and the second medium, the evanescent wave will be different from the one under "ordinary conditions" and it will pass energy across the second into the third medium.

It makes sense now.

electric field disturbance in air at site of tIR decays exponentially w/ distance - it is not a propagating sinusoid, and it doesn't matter anyway because the tiniest proximal particles in the air would scatter the "evanescent field" energy


ETA: what they are talking about is if you have a second piece of whatever substance through which tIR is also occuring and you put them so close together that the evanescent fields overlap you can get actual power exchange

I was assuming a frustrated total internal reflection, based on the higher RI of the oil vs air.

So would the tIR not change in the case of a diamond/metal interface, and the type of setting be irrelevant?

 

[yssie]

I was also able to find this bit of info.

Under "ordinary conditions" it is true that the creation of an evanescent wave does not affect the conservation of energy, i.e. the evanescent wave transmits zero net energy. However, if a third medium with a higher refractive index than the second medium is placed within less than several wavelengths distance from the interface between the first medium and the second medium, the evanescent wave will be different from the one under "ordinary conditions" and it will pass energy across the second into the third medium.

It makes sense now.

electric field disturbance in air at site of tIR decays exponentially w/ distance - it is not a propagating sinusoid, and it doesn't matter anyway because the tiniest proximal particles in the air would scatter the "evanescent field" energy


ETA: what they are talking about is if you have a second piece of whatever substance through which tIR is also occuring and you put them so close together that the evanescent fields overlap you can get actual power exchange

I was assuming a frustrated total internal reflection, based on the higher RI of the oil vs air.

So would the concept of frustrated total internal reflection not be present in the case of a diamond/metal interface, and the type of setting be irrelevant?

The type of setting is certainly important, but yes discussion of this optical coupling phenomenon is irrelevant
When we are considering something like foil-backed rhinestones tIR is not a consideration, what is happening is straight up reflection off that shiny surface

 

[haflc]

The type of setting is certainly important, but yes discussion of this optical coupling phenomenon is irrelevant

So, what would be the optimal setting for performance (if style was not important)?
And why?

Thanks

 

[yssie]

The type of setting is certainly important, but yes discussion of this optical coupling phenomenon is irrelevant

So, what would be the optimal setting for performance (if style was not important)?
And why?

Thanks

Haha and on that you will find hours of reading on here if you care to wade through it all

Just my personal opinion, then: what happens 'numerically' and what the human eyes can see may or may not correlate.
If you want every bit of sparkle you can get you'd wrap the pavilion in a mirror-finish cup - all diamonds leak some light through the pavilion (all the light rays that are smaller than crit angle, in the non-grey zone in the pics). Barring that I'd pick settings that leave as much of the stone open to light as possible - a tension setting, followed by a high-prong open-pavilion type.. halos and closed bezels at the bottom of the list.

'course in the real world noone is going to take a white diamond with a killer cut and wrap it in foil - and I love bezels, and do believe that with well-cut stones any sacrifice is negligible... so with a well-cut diamond I'd say pick whatever setting you want and the diamond will look stunning

ETA: here's a recent fun thread on bezels: rockytalky/does-a-bezel-setting-change-and-or-decrease-light-return-t146618.html

 

[haflc]

just getting as much info as i can before i make my final decision.
learning something new everyday.

thanks for your help.

 

[yssie]

you're very welcome, you are definitely doing your due diligence with this

 

[Andelain]

Yes a dirty ideal-cut diamond can no longer perform as an ideal cut diamond.
Dirt not only reduce the light, it causes it to be sent in the wrong direction.

Be like Kenny - clean your diamond constantly.

There has even been discussions here of what proportions would perform better when diamonds are dirty.

There are some of us who have a reason to want to know that.

 

[stone-cold11]

Yes a dirty ideal-cut diamond can no longer perform as an ideal cut diamond.
Dirt not only reduce the light, it causes it to be sent in the wrong direction.

Be like Kenny - clean your diamond constantly.

There has even been discussions here of what proportions would perform better when diamonds are dirty.

There are some of us who have a reason to want to know that.

I am guessing you mean the last statement?

Shallower pavilion, from the explanation given by yssie. Which is also why HCA prefers a lower pavilion.

 

[Andelain]

Yes a dirty ideal-cut diamond can no longer perform as an ideal cut diamond.
Dirt not only reduce the light, it causes it to be sent in the wrong direction.

Be like Kenny - clean your diamond constantly.

There has even been discussions here of what proportions would perform better when diamonds are dirty.

There are some of us who have a reason to want to know that.

I am guessing you mean the last statement?

Shallower pavilion, from the explanation given by yssie. Which is also why HCA prefers a lower pavilion.

Yes, that was what I meant, thanks. It can be very hard to keep jewelry clean over here, but I still enjoy wearing it.

 

[haflc]

ETA: here's a recent fun thread on bezels: rockytalky/does-a-bezel-setting-change-and-or-decrease-light-return-t146618.html

Interesting link.

I have noticed a significant difference in the way the diamond performs based on what background the stone in set in.

If it is completely covered in the back I notice far less contrast and a bit more white.
If I hold it with forceps at the edges it looks a bit more transparent.
(And every permutation in between)

The major difference is when viewed from an angle.
There is no doubt that light from both the crown and pavilion (as well as from every angle) play a role in how a stone performs.

A diamond no matter how well it is cut will never be able to return 100% of all the light from the crown, and there will undoubtedly be light entering the pavilion that will leak out from the top.

 

[yssie]

ETA: here's a recent fun thread on bezels: rockytalky/does-a-bezel-setting-change-and-or-decrease-light-return-t146618.html

Interesting link.

I have noticed a significant difference in the way the diamond performs based on what background the stone in set in.

If it is completely covered in the back I notice far less contrast and a bit more white.
If I hold it with forceps at the edges it looks a bit more transparent.
(And every permutation in between)

The major difference is when viewed from an angle.
There is no doubt that light from both the crown and pavilion (as well as from every angle) play a role in how a stone performs.

A diamond no matter how well it is cut will never be able to return 100% of all the light from the crown, and there will undoubtedly be light entering the pavilion that will leak out from the top.

Karl did bring up the angle in that thread.. I would wager that the influence of setting on a smaller stone is so much than on a bigger stone, with the bigger stone setting may not matter for purposes of visibility - I would love to see an accurate simulation, one day maybe!