Black arrows

[Daniel B]

*Already done a search- came up empty. . .

Hey everyone~
Whenever I look at a H&A ( Not IS Image) diamond, I find it very distracting to see the black or dark pavillion mains. *Would longer LGF''s lessen this effect? *What other specs can I target to lessen this, also? I think i read somewhere that the only time you notice this is when you look at it head on, right?

 

[strmrdr]

longer lgf% makes them smaller.
The only time you will see it is in indirect light conditions with your head blocking the light.
Some crown/pavilion combos make them stand out more also.

I like seeing em as long as it isnt all the time and they arent too big.

 

[strmrdr]

here is my very poor article on the subject:
http://journal.pricescope.com/Articles/11/1/Hearts--Arrows-Diamonds---Its-not-all-about-light-return.aspx

 

[JohnQuixote]

The only time you would ever see them as dark as in magnified static photographs or ideal-scope images is if you held the diamond absolutely still, and then blocked the light from directly above.

The darkness you see in these photos is caused by 'obscuration.' Those are areas on a diamond where light would normally enter and exit from extremely high angles. The camera is blocking that direct light, so those areas go dark in the static and centered view. The same thing happens when a diamond is still and the viewer's head is directly over it. When unobscured (practically all of the time) those arrows are never so obvious. More info on head shadow, here.

The difference you see in a diamond, unobscured to obscured, is a measure of that diamond's contrast. Remember that diamonds are dynamic things, not static. Much of their beauty is related to movement. With good contrast you will see a sharp on/off quality to the scintillation as the diamond moves. A nice, precise pattern of arrows with contrast is evidence of good cutting and symmetry. Good H&A diamonds are not the only ones that have this effect - many well-cut diamonds show it.

Longer lower halves would narrow the pavilion mains, causing the arrows to become uniformly thinner, presuming that it is cut with good optical symmetry. Too thin and you may sacrifice some of the overall performance in low light conditions.

As an example of the difference contrast via obscuration makes, here are cosine squared images of 2 stones. They are identical, except that a 30 degree cone of obscuration, equivalent to an observer’s head, is present in the one on the right.


Edited to add: I was composing/photo-hunting while you were posting Strm. Actually, I really like that article. As I recall, your comment that "...people's perception of beauty tends to lean towards symmetrical objects being better looking according to several studies" led to some very illuminating discussion and links.

 

[Daniel B]

Date: 11/27/2005 5:04:37 PM
Author: JohnQuixot


Longer lower halves would narrow the pavilion mains, causing the arrows to become uniformly thinner, presuming that it is cut with good optical symmetry. Too thin and you may sacrifice some of the overall performance in low light conditions.

Thanks John and Storm
I, too, liked your opinion piece and the links that followed. . . Great job!

As for the above quote, would 78-79 LGF be a compromise for low lighting performance and a less noticeable arrow pattern in indirect lighting?

 

[strmrdr]

Date: 11/28/2005 12:01:21 AM
Author: Daniel B

Date: 11/27/2005 5:04:37 PM

Author: JohnQuixot



Longer lower halves would narrow the pavilion mains, causing the arrows to become uniformly thinner, presuming that it is cut with good optical symmetry. Too thin and you may sacrifice some of the overall performance in low light conditions.

Thanks John and Storm

I, too, liked your opinion piece and the links that followed. . . Great job!


As for the above quote, would 78-79 LGF be a compromise for low lighting performance and a less noticeable arrow pattern in indirect lighting?

John would agree with that and Id say you can go to 82% or so with top optical symmetry and the proper angles with good low light performance.
You would want the crown angle in the 33.8-34.4 range and the pavilion in the 40.9-41.2 range to pull it off.
great physical symmetry is a plus when walking the edges.
Whats in the averages is going to be important.

 

[Daniel B]

Date: 11/28/2005 12:17:50 AM
Author: strmrdr

John would agree with that and Id say you can go to 82% or so with top optical symmetry and the proper angles with good low light performance.
You would want the crown angle in the 33.8-34.4 range and the pavilion in the 40.9-41.2 range to pull it off.
great physical symmetry is a plus when walking the edges.
Whats in the averages is going to be important.

So 33.8-34.4 and 40.9-41.2 give the arrows a less pronounced appearance (coupled with the 78-82 LGF's)? Is this why you prefer those angles in your stones? To me, wouldn't these angles give the diamond a brighter white light return?

 

[belle]

daniel,
don''t get hung up on the appearance of the arrows. 95% of the time the arrows are going to look bright silvery white. yes, there are certain lighting conditions where they will appear darkish, but you have to remember that diamonds are dynamic. they are constantly moving. it''s not like when you get the stone in lighting that is condusive to the arrows looking darker that there is a solid dark arrow pattern constantly. moreover, if you have a well cut stone, the scintiallation will capture your attention more than the arrow pattern itself. all diamonds have facets that look dark at times, it just so happens that in h&a stones the facet pattern is symmetrical instead of random.

 

[Daniel B]

LOL, Arright Belle, I forgot that 99% of the time the diamond is moving

 

[strmrdr]

Date: 11/28/2005 12:30:47 AM
Author: Daniel B

Date: 11/28/2005 12:17:50 AM

Author: strmrdr


John would agree with that and Id say you can go to 82% or so with top optical symmetry and the proper angles with good low light performance.

You would want the crown angle in the 33.8-34.4 range and the pavilion in the 40.9-41.2 range to pull it off.

great physical symmetry is a plus when walking the edges.

Whats in the averages is going to be important.

So 33.8-34.4 and 40.9-41.2 give the arrows a less pronounced appearance (coupled with the 78-82 LGF''s)? Is this why you prefer those angles in your stones? To me, wouldn''t these angles give the diamond a brighter white light return?

you have been paying attention in class :}
In the right light they have enough fire not to look dead.

In rounds i like bright diamonds.
If I want a very very fiery stone ill get an asscher. :}

 

[strmrdr]

Which brings us to the next issue contrast brillance.
long lgf% diamonds can suffer in this area.
shorter lgf% do provide more contrast area in some lighting conditions but go too short and they are too dark looking.
Thats the real trade off with long lgf diamonds.
But you stated you didnt like the arrows poping as much ao you would get what you asked for :}

When it comes to diamond design there is no free lunch change one thing and it always changes another.
Lighting will always be the biggest variable and one that is beyond the cutters control.

 

[JohnQuixote]

Date: 11/28/2005 12:17:50 AM
Author: strmrdr

John would agree with that and Id say you can go to 82% or so with top optical symmetry and the proper angles with good low light performance.
You would want the crown angle in the 33.8-34.4 range and the pavilion in the 40.9-41.2 range to pull it off.
great physical symmetry is a plus when walking the edges.
Whats in the averages is going to be important.

I would amend Strm''s perception of my preferred range to include 80% as long as the optical symmetry is tops.

The CA can range a few tenths up and the PA slightly down in well-cut diamonds as well. I''m a little wary of 41.2 PA as an old rule, but admittedly have seen far less 41.2/XX.X combos than all of the other possibilities in this range. I would not be opposed to viewing more of them.

Some of this begins getting into matters of taste. Strm, are you going to start talking about main crown angle versus upper halves relative to contrast?

 

[Daniel B]

Date: 11/28/2005 12:58:56 AM
Author: strmrdr


you have been paying attention in class :}

In the right light they have enough fire not to look dead.
The right light? You mean dim or candle light, right? Or even in Flouro it can still throw some shards of fire out? (just making sure, thanks!)

 

[Mara]

i also second belle's comments...i see my dark arrows maybe once every few weeks. the rest of the time they blend in with the diamond or i can make them out in indrect light in the car but they are more silver or opaque. it really depends on lighting, but i am not in that type of environment where i see super dark arrows very often at all. i do love seeing the arrows though when i do get a glimpse of them, it's like a treat in the stone. for me the arrows make the stone. but i know they are not for everyone!! but you do not see them in that same photo environment like we do here on PS in the vanity shots. real life diamond viewing is very different.

 

[valeria101]

Arrows are a good thing... IMO, it is a nice way to distribute extinction around the stone. Otherwise to avoid any extinction and still have great brilliance you''d end up with some top heavy expensive diamonds.

 

[Daniel B]

Date: 11/28/2005 2:18:54 AM
Author: Mara
i also second belle''s comments...i see my dark arrows maybe once every few weeks. the rest of the time they blend in with the diamond or i can make them out in indrect light in the car but they are more silver or opaque. it really depends on lighting, but i am not in that type of environment where i see super dark arrows very often at all. i do love seeing the arrows though when i do get a glimpse of them, it''s like a treat in the stone. for me the arrows make the stone. but i know they are not for everyone!! but you do not see them in that same photo environment like we do here on PS in the vanity shots. real life diamond viewing is very different.

Hey Mara~
I was only concerned because when I viewed an H&A at one my local BandM''s I could really notice the black arrows looking right down on it- and it was still under those nice store lights-- I''m not worried about it now though, you guys assured me enough it will be ok

 

[valeria101]

Date: 11/28/2005 3:22:25 AM
Author: Daniel B

I was only concerned because when I viewed an H&A at one my local BandM''s I could really notice the black arrows looking right down on it

It was your looking very closely that made the arrows appear. They reflect anything between the table of the diamond and the main light source.

You will keep seeing them if looking at the diamond from very short distance (=''couple of inches) - and this is very unusual for viewing jewelry (so Mara''s story fits perfectly) anywhere but in a jeweler''s shop.

 

[strmrdr]

Date: 11/28/2005 1:55:39 AM
Author: Daniel B

Date: 11/28/2005 12:58:56 AM

Author: strmrdr



you have been paying attention in class :}

In the right light they have enough fire not to look dead.

The right light? You mean dim or candle light, right? Or even in Flouro it can still throw some shards of fire out? (just making sure, thanks!)

strongly diffused lighting produces very limited fire in any diamond.
The best lighting for fire is direct pinpoint lighting from mutiple sources.
Non-diffused light is what I was talking about.

 

[Garry H (Cut Nut)]

Daniel I have made a video to show you this effect.

Please click on the new video link above this post and go to the one on head obstruction.

Everyone please excuse my ameuterish begginnings at editing video''s

 

[Daniel B]

Garry I saw the video, and I thought it proved a good point! I like your store too, it''s nice

And Val- I think I was looking at it pretty close within a few inches, youre right!

 

[strmrdr]

33.8 41.2 56% table 50% stars 82% lgf%

bright, arrows while different arent going to be popin either.
Its not a traditional h&a but tightly cut I think it would make a kicken diamond.

 

[strmrdr]

Date: 11/28/2005 1:30:44 AM
Author: JohnQuixote

Date: 11/28/2005 12:17:50 AM

Author: strmrdr


John would agree with that and Id say you can go to 82% or so with top optical symmetry and the proper angles with good low light performance.

You would want the crown angle in the 33.8-34.4 range and the pavilion in the 40.9-41.2 range to pull it off.

great physical symmetry is a plus when walking the edges.

Whats in the averages is going to be important.

I would amend Strm''s perception of my preferred range to include 80% as long as the optical symmetry is tops.

addition noted, but i didnt say ya wouldnt add one on to it just that ya would agree that they be good ones :}

I''m a little wary of 41.2 PA as an old rule,

old thinkin dies hard. id like to see more of them cut,, with the proper crown angles of course and make em tight so tight there is no daylight between the cracks. gota love them kewl arrows that one would hardly ever see if ever.


Some of this begins getting into matters of taste.
diamond tastes sweet

Strm, are you going to start talking about main crown angle versus upper halves relative to contrast?

not tonight but might start talking about gravities effect on diamond performace and how holding the diamonds table at an angle to the ground returns more light to the viewers eyes.

we need a clown face smiley.

 

[JohnQuixote]

we need a clown face smiley.

33.8 41.2 56 50 79

(ho ho ho)

 

[valeria101]

About this 80%....


Is it too wrong to say that very long lgf have similar impact on scintillation as the very short ones? i.e. you get some larger patches on the pavilion only in one case these are the mains and in the other the lgf? Those would not be of quite the same shape... but in terms of the usual light return & scintillation terms the beasts would run along closer than it sounds from the numbers. Wrong?

 

[Garry H (Cut Nut)]

The optimum length of lower girdle facets depends on many factors

the diamonds size is one very important one

 

[valeria101]

Date: 11/29/2005 6:48:11 AM
Author: Garry H (Cut Nut)

The optimum length of lower girdle facets depends on many factors

the diamonds size is one very important one

You have mentioned this before... about some AGS cut study judging proportions dependent on size. Sounds great, wish there was more said

 

[strmrdr]

Date: 11/29/2005 2:01:55 AM
Author: JohnQuixote

we need a clown face smiley.

33.8 41.2 56 50 79


(ho ho ho)

rofl

 

[strmrdr]

Date: 11/29/2005 5:23:28 AM
Author: valeria101
About this 80%....



Is it too wrong to say that very long lgf have similar impact on scintillation as the very short ones? i.e. you get some larger patches on the pavilion only in one case these are the mains and in the other the lgf? Those would not be of quite the same shape... but in terms of the usual light return & scintillation terms the beasts would run along closer than it sounds from the numbers. Wrong?

too complicated for a short post but thats on the right track.
With a long lgf% the lgf facets play a bigger role in driving light return than with short lgf%.
Where it switches from primary one to the other would make an interesting study.
I think it wouldnt be constant accross different c/p combos.

edit: for those trying to following this:
short lgf% means the pavilion facets are bigger.
long lgf% means the pavilion facets are smaller.
Its the size of the pavilion facats that determin the arrows size.
The crown/pavilion angle and the lgf% both play a role in how often they are seen as standing out.
As with anything else with diamonds it comes down to lighting lighting lighting.

 

[diamondsrock]

stmr - what would your absolute ideal diamond specs be?

 

[strmrdr]

Date: 11/29/2005 5:31:55 PM
Author: diamondsrock
stmr - what would your absolute ideal diamond specs be?

an asscher with a 12%-15% crown height and kicken patterns. :}

in rounds there are a lot of formula's for bright diamonds.

There is someting about diamonds with tight physical symmetry that appeal to me beyond looks so it would have to be tight.
Say no more than .1 on the pavilion and .2 on the crown.
34.2-34.4 crown pavilion of 40.8-40.9
lgf% of 81%
stars 58%
Table of 56%
med girdle with the upper girdle facets cut for contrast.

That would be a realistic one.
It would produce a very bright diamond with an acceptable amount of fire and contrast.
Brighter combos exist but there would be more tradeoffs in some of them.

edit typo, thinko