dark spot in center of princess cut diamonds?

[slg47]

Hi everyone-when looking at pictures of princess cut diamonds online, many of them exhibit a 'dark spot' directly in the center. What causes this, how visible is it in real life, and how can it be avoided (or is it just something intrinsic to the faceting of princess cuts?)

Thanks
SLG47

 

[Serg]

Most probably it's nailhead phenomena ( head reflection in diamond) if you saw 4-6 black spots(VF's) .Such black spots could be easy visible in normal illumination too .

 

[yssie]

I thought just table reflection, like the culet area in RBs -

 

[slg47]

yes yssie, that is what I was referring to. some princess cuts seem to show this more than others. when you say table reflection...what does that mean?

 

[yssie]

In this thread [URL='https://www.pricescope.com/community/threads/optimal-agsl-light-performance-map-question-area-above-culet.148354/']https://www.pricescope.com/community/threads/optimal-agsl-light-performance-map-question-area-above-culet.148354/[/URL]

John Pollard's quote - Unlike the other parts of the ASET image, that small circle over the culet is not primary light return. What you are seeing is a reflection (in the bottom of the stone) of the underside of the table facet... Imagine that you are inside the diamond looking up. What do you see? The large, flat table facet reflecting back down on you like a mirror - and since you're a reflective surface yourself you re-reflect that reflection back up again. So what we're seeing from above, in this static situation with controlled lighting, is a tiny reflection-of-a-reflection.

Which is just very cool

And pics of the same in an RB (well sorta, best I could do in a couple of mins )

 

[slg47]

oh ok, thanks! in some princess cut photos that area definitely appears darker, but I suppose that is nothing to be concerned about (and likely due to differences in photography as much as other more meaningful differences). I am not shopping for a princess but just curious. thanks!

 

[Paul-Antwerp]

I see no reason to link A in rounds to B in princess-cuts.

I may be mistaken but I think the dark center-area in the princess is light-leakage. The reason for it being green in many ASET-photos is due to the incorrect ASET-photography.

Live long,

 

[Serg]

.

 

[yssie]

I see no reason to link A in rounds to B in princess-cuts.

I may be mistaken but I think the dark center-area in the princess is light-leakage. The reason for it being green in many ASET-photos is due to the incorrect ASET-photography.

Huh. So - you would see your finger - or the bottom of the setting - through clearly?

So here is one where it looks to be 'leaking' by white in ASET




but here is one where ASET is again green.






How does that ASET happen?


Edited to add IS pic

 

[yssie]

.

Serg - I'm afraid I'm not sure what to look for in your pics, would you mind adding a bit more info so I can follow?

 

[Serg]

.

Serg - I'm afraid I'm not sure what to look for in your pics, would you mind adding a bit more info so I can follow?

Yssie,

Do you see Black VF's under table( not near culet)? I showed raytracing for such black VF's. It's are typical nailhead VF's

 

[yssie]

Yssie,

Do you see Black VF's under table( not near culet)? I showed raytracing for such black VF's. It's are typical nailhead VF's

Ah - yes, that I see. Thanks!


The idea of a princess with a pseudo-culet is intriguing. I can't say I've ever noticed this effect (but maybe seen, and not noticed, though).

 

[Garry H (Cut Nut)]

The cause of this leakage is when the pavilion angle (the facets running down from the corners) are less than 39.2 degrees.
Rays or your line of sight from directly above do not leak out directly.
However overall many proportion combinations work quite well when this effect shows.
Many AGS zero princess suffer this effect. Peter Yantzer has commented in support of it some years back.
I test stones with about 5 degreees of tilt with an ASET or ideal-scope and reject (even AGS 0) stones where the leakage does not disappear on each side.

 

[steveaastin]

The Princess is a brilliant-style shape with pointed, uncut bends. It is typically cut perfectly square. Brilliant style refers to vertical-direction crown and pavilion facets that are wide at the culet and narrowed toward the strap, the opposite of the pavilion-facet arrangement on a curved-corner radiant. A Princess generally has 76 facets, giving it more brilliance and fire. Because of the 76 facets you get such a dark spot.

 

[Garry H (Cut Nut)]

The Princess is a brilliant-style shape with pointed, uncut bends. It is typically cut perfectly square. Brilliant style refers to vertical-direction crown and pavilion facets that are wide at the culet and narrowed toward the strap, the opposite of the pavilion-facet arrangement on a curved-corner radiant. A Princess generally has 76 facets, giving it more brilliance and fire. Because of the 76 facets you get such a dark spot.

Hi Steve, I guess your new around here.
Did you understand my post just above yours?
The stone could have 30 or 200 facets and still have the dark spot. Have you seen a princess cut with 76 facets? I guess it was pretty big?