Question about dark arrows

[christarose]

Hi everyone,

I''ve been browsing for some diamonds (for a 3-stone anniversary ring), and I noticed that many of the "best cut" stones have visibly dark arrows from the top view. Why is this? I know everyone likes seeing the arrows, but I don''t particularly find the dark centres that attractive. Is it related to the contrast & how firey the sparkles will be?

 

[WinkHPD]

The light in a diamond comes from three areas relative to the table of the stone. The dark arrows are actually a reflection of the head shadow and from across the table in a restaurant they will be bright flashes of light as the head will no longer be blocking the light. This light is coming from and angle of 90% (perpendicular to the table out to about 80% (10% from perpendicular) ***

*** These are not the exact angles and are given for illustrative purposes only. Please do not take me to task for not being totally correct, I am not a cutter and am giving a broad idea only.

So when you are looking at a stone and see those dark arrows, you are seeing actually a very small reflection of your head, but when seen from further away you will see very bright flashes of light coming from these same areas.

If you look at the enclosed photo you will see the black areas that come from this cone of light and the red areas that come from an area of outside the cone down to approximately 15% or nearly parallel to the table and then pink light from the furthest angles until actually reaching paralell with the table.

The areas of white light in two of the three stones are where light is leaking out the bottom, or in this case in from the bottom.

This will give you an idea of where the light that is coming out the top of the stone is coming from. Although the "dark" areas may not look as good when your head is blocking the light, they can actually look very good to an observer who is not as close to things as you are. Of course you can get too much black and then there is not the on/off flash that makes the diamond seem to sparkle and blaze as it is moved ever so slightly by any relative motion between the observer and the diamond.

Simple answer, yes they are related to contrast and how the diamond will look, but no they are not particularly related to the fire or dispersion of the diamond which is determined by the relationship of the pavilion and crown angles, although a stone cut well enough to have the arrows that you are referring to will normally be highly dispersive as well.

Wink

P.S. This is a small overview of an extremely complex subject to which I do not claim to be totally conversant in the details, but rather only in the overview.

 

[Brian Knox]

Hi,

Ask to look at the different quality diamonds in natural lighting or a combination of flourescent with incandescent.

Ideal cut diamonds will look dark in incandescent only lighting.

Natural light is the best light for buying diamonds.

 

[christarose]

Thanks for replying! So Wink are you saying that other observers will get a better view of the diamond than I will??

Brian, here's an example of what I'm describing...I've seen photos like these (I don't know what the lighting conditions were)...perhaps the arrows won't be as visible in person?

 

[verticalhorizon]

In an ideal cut diamond (RB in this case), those arrows will be visible... sort of. You have to keep in mind, most of the pictures you see online are under 10-30x magnification. You'd have to be pretty close to see it like you see in your examples. Plus, in various lights, those otherwise dark area will be obscured by the brilliance and scintillation.

 

[Magnum]

my stone is 0.614 carats, so I do not see the arrows that clearly with the naked eye in diffuse light (although i do notice the contrast the arrows are creating and I think it adds to the look of the diamond), which I think is similar to the light those pictures were taken in, but I'm not sure. Under higher magnification, the arrows are clearly visible, though. I can see individual arrows very clearly in direct light when they catch the light and both the arrow shaft and tip light up. I think it's a cool effect.

You don't have to be an observer to appreciate it. If your head is between the light source and the diamond, and you hold the diamond a little off to the side at a slight angle (outside the shaddow of your head) you will see the arrows light up and witness a cool light show.

 

[Brian Knox]

Hi christarose


It will be much less pronounced in the diamonds in your ring .

But do go look at some in natural lighting just so you can see for yourself.

 

[valeria101]

Week diffuse light is not great for looking at diamonds unless you want to inspect the shape of the facets precisely. I am sure those pictures were taken with the purpose to show off the arrow pattern and one needs carefully controlled conditions to acheieve this. In more mundane lighting conditions (which usually means stronger light source and/or direct light) such detail will be flooded by brilliance - not good if one wants to see that H&A bardge of honor!

There obviously is a tradeoff - no darkness seen upclose means no light flash at arm's length. As far as I understand, this remains true for all diamond cuts, not just the round - only that the dark areas may be more scaterred and no pattern readily identifiable in other shapes.

Same story for non H&A diamonds with strong light return: there will be some reflecting areas, but not as eye catching as those arrows everyone points out to. For example... this stone (LINK). Also, the thickness of those arrows may vary so that they get more or less prominent (and so does the associated light flash) with little compromise in overall light return (examples down this LINK).

Yours is an interesting question - given that quite a few chase those arrows like some Holly Grail !


Hope this helps

 

[Garry H (Cut Nut)]

Check out the Novemeber newsletter on the front page left side tool bar


http://www.ideal-scope.com

 

[christarose]

Thanks again for your help! I know it's good to see those arrows since they denote an excellent cut - but I was glad to hear that they'll light up and not be dark (like those photos) in most light conditions.

 

[limey]

Wink, Thank you for such a great post. I have never seen it explained so well and I learned alot in the process!!

 

[WinkHPD]

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On 5/19/2004 1:50:58 PM christarose wrote:

Thanks for replying! So Wink are you saying that other observers will get a better view of the diamond than I will??

Yes, quite frequently the stone will look much better at arms length or greater than it does up super close and personal. It is one of the phenomina that people notice about EightStars. Up real close it is often difficult to tell an EightStar from a top quality H&A stone, but sitting accross the table from someone who is wearing both of them is a real eye opener.

This happened to me one evening when I was having dinner with two ladies who own EightStars. One of them was wearing an EightStar of 1.75cts and a H&A of 2cts. Up close both were extraordinarily beautiful stones, but sitting across the table from her the EightStar really danced rings around the other stone. We all got to talking about it and pretty soon the owner had the other lady put her rings on so she could see the effect and she was delighted.

I believe that Steve L had sold her both stones, I know for sure that he made the ring for the EightStar, WOW what a craftsman he has working for him.

Wink

 

[WinkHPD]

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On 5/20/2004 12:07:51 PM limey wrote:

Wink, Thank you for such a great post. I have never seen it explained so well and I learned alot in the process!!----------------

You are welcome. Please remember though that that is the tip of the iceberg for a very complex process and the angles that I gave are only an approximation as I do not remember the exact numbers, and I suspect that the exct numbers change from stone to stone as the relationship between the crown and pavilion changes.

Wink

 

[Rhino]

I would concur Wink's statement about the arrows. I would not say this is exclusive to 8* diamonds but what Wink is saying about head obstruction etc is right on. You should see how those facets light up in ambient light conditions! Wink, I recall you doing an observation under a shaded tree outside on a sunny day. I have seen this phenomena too and is a great ambient light observation. The pavilion mains (or areas of black within red reflector technologies) light up like a christmas tree when the head is not obstructing and contribute to many secondary reflections within the diamond being observed.

 

[limey]

Thanks you guys for breaking it down to something the peeps can follow, but even at its simplest level it still sounds like a physics lesson...

blah, blah, blah head obstruction blah, blah, blah ambient light blah, blah, blah phenomena blah, blah, blah pavilion mains blah, blah, blah black within red reflector technologies) blah, blah, blah secondary reflections within blah, blah, blah

so let me translate...

Ideal cut H&A's are not just rocks, they rock!! Get yourself an IdealScope (link is above) and arm yourself with enough knowledge to get a pretty stone.

 

[limey]

for some reason I want to drop F bombs to describe how bloody amazing ideal cut diamonds look...

 

[WinkHPD]

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On 5/20/2004 1:21:12 PM Rhino wrote:

You should see how those facets light up in ambient light conditions! Wink, I recall you doing an observation under a shaded tree outside on a sunny day. I have seen this phenomena too and is a great ambient light observation. The pavilion mains (or areas of black within red reflector technologies) light up like a christmas tree when the head is not obstructing and contribute to many secondary reflections within the diamond being observed.----------------

Rhino,

Under a broad leafed tree on a sunny day is okay, but it you want a magical dispersion show, it works best on an overcast day. I took one of Paul Slegers' Venus brand stones, an EightStar and a run of the mill near ideal stone for a tour with a client yesterday. We stepped out of my well lit office (well lit, but no klieg lights) into a poorly lit hallway, then down the stairs into a dark corner. My client literally stood facing into the corner and looked at the stones with almost no light and observed the stone's performances. Then we stepped outside into the shade of the tree. It was overcast with practically no visible shadow for the shade but, as my client said...

"OMIGOSH! These are INCREDIBLE!" While the run of the mill stone looked nice, the other two were blazing balls of colors. Reds, blues, greens and yellows came flying out of the stones. It made part of my client's choice easy! The near ideal cut went quickly back into the paper. As for the rest of her choice, well, that was much more difficult and not relevant to this thread. Suffice it to say she got an incredible diamond...

Wink

 

[WinkHPD]

Or as Limey says,

"Blah blah blah, OMIGOSH! These are incredible!" Blah blah blah, freaking incredible! Blah blah blah

Wink