Letting light return guide our selection process

[oldminer]

Let's just say several 1.00ct round diamonds of various proportions happen to give us nearly equally high light return measures. Due to their different cutting styles they are all different depth percentage stones.

Just suppose a hypothetical Tolkowsky range diamond in this group has a depth of 60.5% and happens to have a diamater of 6.4mm. The other diamonds ain this group are all of different depths and diameters, yet they all still weigh 1.00ct.

1. Do you think other diamonds in this group of stones with SMALLER diameters and DEEPER depths are worth a bit less, more or are equal in value to the hypothetical Tolkowsky range diamond?

2. Do you think other diamonds in this group with LARGER diameters and LESS depth are worth less, more or equal to the value of the hypothetical Tolkowsky range diamond?

3. If the depth becomes extremely deep or extremely shallow, yet the light performance remains virtually equal, due to very smart cutting, is there a point where the value will go down due to lack of visual size or lack of durability?
Where do you think this downturn of value would happen?
What depth or lack of depth are a crucial breaks in terms of value?

4. Lastly, what depth or lack of depth constitutes a step down from IDEAL cut no matter how great the light return measure is?

THANK YOU FOR ANY AND ALL REPLIES....

 

[Serg]

http://www.gemology.ru/cut/english/podrobno_1.htm

 

[oldminer]

Sergey: How does the chart anwser any of the questions about $$$$VALUE? Are there some words of explanation that did not post?

 

[strmrdr]

My opinion is that pure light return is just one of many things that makes a great diamond great.
If that light return isnt returned in a manner that results in light returned to the eye when viewed on the finger in real world conditions versus return in the store looking down on it that doesnt do the same on the finger in the real world isnt good for anything.
All brilliance and no fire makes for a very dull diamond.

1> less
2> depends on real world return.
3> yes
depends and will take a longer answer than I care to give at this time.
4> YES see the first line of my post.

 

[Hest88]

Hm. Fascinating if the industry ever moves away from valuing diamonds in terms of carat weight.

1) Should be worth less.

2) Depends on whether or not the shallowness affects performance.

3) The basic answer is yes, it should be worth less, and that should happen when I, a normal consumer, can tell the visual difference or when. I can''t give you MM right now, but if the evaluations are done I suspect someone will come up with those breakpoints.

4) Again, for me it''s all about the visuals. A diamond will be worth less if it looks smaller or is so spready that it looks glassy, even if the actual light return is the same.

 

[Garry H (Cut Nut)]

hi Dave,

I think your question and title might not be leading people as and where you intended?

If it said something like if you had absolutely equivalent diamonds from a light return and beauty point of view - all of the same weight - but they were different from a diameter and other physical dimension and proportion data - would you dah dha dah dah etc
Is that what you mean?


BTW Sergey''s chart shows a bold black line that represents the Tolkowsky light return for various combinations of crown and pavilion angles - but i hink you mean more than just light return - you mean over all desirability?

 

[valeria101]

Price by size...

Well, a bit back I went through the PS database of emerald cuts to see if size (surface area) is a strong pricing facor or not. On average it appeared to be a close second after carat weight, and that''s with total disregard for brilliance. Adding a measure of light return on top, size would become a even stronger factor if not correlated with size (as in your hypothesis).

I guess Leonid can do something similar much faster than I can download those spreadsheets from the wrong end.

 

[oldminer]

Garry: Your re-wording of the question is fine, but it would seem that we have little opinion here that answer the questions raised.

"If round diamonds of fine light performance and fine diamond-like apearance are cut differently but weigh the same, where do the price breaks come based on overly deep or overly thin parameters?"

It is a complex question although it might seem easy on the surface....

Any viable answers?

 

[strmrdr]

Date: 12/3/2004 7:14:27 AM
Author: oldminer
Garry: Your re-wording of the question is fine, but it would seem that we have little opinion here that answer the questions raised.


'If round diamonds of fine light performance and fine diamond-like apearance are cut differently but weigh the same, where do the price breaks come based on overly deep or overly thin parameters?'


It is a complex question although it might seem easy on the surface....


Any viable answers?

Would be nice if knew it when I see it was a viable answer.
I know what I look for but some of the new cuts are rewriting the rules as I know them.
So im waiting for the info from you and the other experts before I decide.
This type of question really requires first hand diamond in the hand data before it can be answered.

For example a 5.5MM 1ct asscher might be a totaly awesome diamond and the top of the line.
A 5.5mm 1ct round is likely a dog even with high return but there are some gemstone cuts out there in rounds that give patterns that look totaly kewl that would call for deep rounds and a 5.5mm 1ct may be acceptable in them if they work cut in diamond.

The majority of the new cuts are nothing more than the old gemstone cuts applied to diamonds sometimes slightly modified sometimes not.

 

[oldminer]

Strmdr: You are confusing the question. I am ONLY asking about ROUND diamonds. We all can say we can tell a good stone from a bad one, but with AGS, GIA and my own lab about to embark on GRADING the quality of light behavior, a complex subject, who has the GOLDEN STANDARD for where the finest steps into the next category below? Is it only a visual degradation, or will it be sort of like the break between VVS1 and flawless,,,,invisible for nearly anyone?

I don''t want to get into light modelling, but just keep try to discover if there are valid opinions about proportions that still apply in most people''s minds. Then I want to know if value will be affected by diameter/depth changes if light remains the same...

I was looking for some technical answers such as "diamonds with crown angles <29 degrees are no good, or diamonds with ext thick gridles or no good, or round diamonds above 65% depth are no good".....something in this subject range from some of the experts in attendance on Pricescope.... So far the answers seem about as vague as my own limited knowledge in the science of light performance and I have been studying this for a pretty long time and don''t have the answers.

 

[Serg]

Date: 12/2/2004 3:50:59 PM
Author: oldminer
Sergey: How does the chart anwser any of the questions about $$$$VALUE? Are there some words of explanation that did not post?

Hi, David.

I wanted to publish two maps. First map is how LR depends from Angles, Second map should be how mass depends from angles for specified diameter.Deviation of mass( spread) could explain part of division of price if Beauty is same. LR could show zone with different Beauty.

But I did not find map for mass. I will recalculate it and send in next week.

 

[valeria101]

Hm... I expect that Serghey''s chart will settle the semantics between David and Garry. If I understand it right,

the question sounds like:

"would you pay more for the one of two rbc that looks a tad larger, but weighs the same and glitters the same as the other"

To this, the answer can hardly be "no". The stats mentioned above say the same, IMO.

Serghey''s chart will say if "glitters the same" needs some licence (=if reallysome visible difference of size can be achieved with the same optics). As usual, what is "visible" remains everyone''s guess. I need half a milimeter of diameter to start caring about size but there are loads of posts here that convey serious concern over 0.1! And what it takes to have a sensible downgrade of optics to achieve significantly more spred, it''s again a ''guesstimate''

Assuming I got this right...

here''s a fun fact: on a list of 50 or so diamond cut brands, there seem to be enough made on purpose to achieve spread with acceptable optics and quite a few made with the purpose to keep weight in with acceptable optics. So to each his own. Since all these survive hand in hand, both the carat number and surface seem to have viable appeal.
At least, as far as I understand these things.

 

[RockDoc]

Hi David


This is a difficult set of questions, but if I understand them correctly you''re asking for value differences that at this time are pre-mature.

The bulk of consumers don''t have light return reports. So the differences in prices are mainly set by dealers that sell to brokers and other resale entities.

The reason I say premature is that light return analysis may differ by the machine used, the person doing the analysis and how he does it. Diamonds with exceptional light return for which the light return is supported by excellent propertions are propbably the most desired by those consumers that are informed. The value sn dollars and what differences they might render vary too. Take the LK ideal diamond as compared with the Eightstar. If the majority of consumers are informed about both diamonds, then there will emerge a more popular diamond, which may sell for more money than not. Light return and its style of return what light or colors where in the stone as well as the strength of the return may also be subject to individual taste.

I think with the machines evolving and GIA/ AGS''s change of stance, we''ll know the answers as sales reports will demonstrate prices reductions or increases.

I think we have to see the recent changes take hold, and then we''ll see the results and any value changes that emerge.

Regads

Rockdoc

 

[laney]

Light return being equal

Diameter would be what I would choose overall all things.

As a pure consumer - looking at a stone... if I saw three "sparkly" stones... I would naturally want the "bigger" looking stone And as a consumer - I look at the top of the stone for this.

Size matters

Oh, and yeah I would expect it to cost more.

 

[Garry H (Cut Nut)]

Folks I do not think Dave and I are disagreeing.
I understand where you are coming from Dave - that is why HCA and DiamCalc each have a spread factor.

Sorry if this takes us a little off task - but it is an attempt to consider the effect on the market of GIA''s new grading system (it will be up soon in Leonid''s new ''journal'' as an entry to review of the gIA Foundation article)

 

[valeria101]

New pricing... looking between the lines of your post Garry,

the prediction of a widening price gap appears to rely on the assumption that the demand for higher cut grades will outrun any attempt for the lower graded (by GIA cut grades) stones to be recut into higher cut grades.

If this judgement is indeed relevant, the actual process seems particularly difficult to predict.
However, a few posts back you mentioned that as much as half of the RBC cut to ideal proportions now are not marketed as "ideals". Could this stock (with newly found pedigree) bridge the gap until a new production cycle tage GIA cut grades into account?

 

[Rhino]

Date: 12/2/2004 3:20:34 PM
Author:oldminer
Let''s just say several 1.00ct round diamonds of various proportions happen to give us nearly equally high light return measures. Due to their different cutting styles they are all different depth percentage stones.

Just suppose a hypothetical Tolkowsky range diamond in this group has a depth of 60.5% and happens to have a diamater of 6.4mm. The other diamonds ain this group are all of different depths and diameters, yet they all still weigh 1.00ct.

1. Do you think other diamonds in this group of stones with SMALLER diameters and DEEPER depths are worth a bit less, more or are equal in value to the hypothetical Tolkowsky range diamond?

IMO a tad less in value. The cutting factory that can optimize both optics and weight should be rewarded for such. Of course there is value in optimizing optics (we purchase diamonds because of their beauty which is directly related to their optical properties) but the one excelling in both should be valued a little higher I would think.

2. Do you think other diamonds in this group with LARGER diameters and LESS depth are worth less, more or equal to the value of the hypothetical Tolkowsky range diamond?

If it can produce optics equal to or better than Tolkowski, yet maintain that *larger* appearance, then I would say worth a little more.

3. If the depth becomes extremely deep or extremely shallow, yet the light performance remains virtually equal, due to very smart cutting, is there a point where the value will go down due to lack of visual size or lack of durability?

This is key. IMO when the diamond is notably smaller looking (due to it being too deep), the diamond should definitely take a hit in value and at the same token, if the stone is too shallow, to the point where it becomes a durability problem then conversely it should take a hit in value as well.

Where do you think this downturn of value would happen?

There would have to be critical points or "thresholds" where the line would have to be drawn. Ie. If a 1ct round diamond has a diameter of 6.4 or 6.5mm I don''t think this is a big whoop. However once you get down to 6.3mm this is a notable difference in size and while it doesn''t sound like much, is enough of a difference that it can be detected with the human eye. On the flip side ... if you have a stone too shallow and the crown is notably too thin, enough to cause potential risk to the stone (btw this too can be detected with the eye) then value should take a hit IMO.

In the first case the threshold should be where the human eye can detect the size differences. In the 2nd case a crown angle must define the threshold of potential risk regardless of the optics.

What depth or lack of depth are a crucial breaks in terms of value?

I think I answered this in my last sentence. Personally, with regards to rounds I don''t even consider stones with a 63% depth and tend to shy away from those in the high 62.x range. When I see depths fall below 60% that too raises a red flag with the Rhino.

4. Lastly, what depth or lack of depth constitutes a step down from IDEAL cut no matter how great the light return measure is?

I''m following ya. Heh... not to sound redundant but I think my last sentence answered your question.

Are we thinking along the same frequency Dave?

Peace,

 

[JohnQuixote]

Date: 12/3/2004 8

0:45 AM
Author: oldminer
I was looking for some technical answers such as ''diamonds with crown angles <29 degrees are no good, or diamonds with ext thick gridles or no good, or round diamonds above 65% depth are no good''.....something in this subject range from some of the experts in attendance on Pricescope.... So far the answers seem about as vague as my own limited knowledge in the science of light performance and I have been studying this for a pretty long time and don''t have the answers.

Dave,

Overall, I''m largely in agreement with the friendly Rhino and Laney: Given stones with equal overall visual performance the larger diameter should command a premium due to larger face up appearance.

More technically, I believe Rhino''s assessment of stones with depth >62% being less desirable is valid (though my upper limit would be 61.5%).

Other specifics on proportions are difficult, because we stray into personal preference for the visual balance in the stone. Sure, we can talk specifically about table size, crown/pavilion angles, lower girdle facet %, etc... But then we sojourn into the oft-debated land of the balance of brilliance/fire/sparkle/DCLR/WL/chromatic flare/tastes great/less-filling/contrast/tomato/to-mah-to etc.

 

[PinkishFlower]

In my diamond''s defense, the Holloway Cut Adviser returns the following result for what you deem to be a shallow diamond:

Selected: 57% depth, 61% table, 34° crown angle, 40.5° pavilion angle
The result is for a symmetrical diamond with a medium girdle and very good polish

Factor Grade
Light Return Very Good
Fire Excellent
Scintillation Excellent
Spread or diameter for weight Excellent

In this consumer''s opinion, the table and depth percentages alone don''t determine the value of a diamond. The angles make a big difference.

Experts assign the dollar values to the stones. In the end, the consumer''s preference will determine whether the price is too high, or too good to pass.

My preference is a larger table. I would have preferred a depth of 61%, but that would have set the stone out of my price range. My diamond took a hit in price because of the depth and I got a sparkly diamond I could afford.

The initial question is a good one. Here''s a diamond with excellent fire and scintillation. How much of a price cut should it endure?

If the ideal depth for this 1.03 ct. diamond is 61% and table 57%, and this diamond has depth 57% and table 61% should the price be 50% less than that of the diamond with the ideal measurements? 25% less? ??% less?

 

[Garry H (Cut Nut)]

PinkFlower it is not that any organization or person sets the pricing - it is the market.
I agree with you that the market is quite silly with the way it priced your diamond

 

[windowshopper]

how about when the visual size appearnace exceeds or falls short the exact carat weight------------------at either point it should start reducing the the price

 

[oldminer]

We may see a few results from knowing more about light performance in the coming years. Poorly cut stones will undergo re-cutting more often. Plenty exist in inventories that will go to the cutter once the right numbers are known. There is little reason to cut poor make diamonds if technology leads the cutting industry.

High performance, but thin diamonds may well become the common stones in earrings and pendants where
durability problems won''t be a factor as it would in a ring. I suspect overly deep diamonds with high performance will be less costly per carat because of weight retention, so they will be the price conscious form of the "ideal cut" and probably called "Near Ideal Cut" or "Premium Cut". Many of these somewhat deep stones are already branded cut stones, so we know some can be successfully sold.

The differences in value Garry mentioned may remain, but I''d predict this will be a short term affair, as the largest discounted material will pay to recut. Not only will it be profitiable to recut these dogs, but they will sell faster...Turn of money in tight profit markets as diamonds have become is a key element.

I think we have established that "too deep" is a detriment to rounds somewhere 62% or more. NOW< how about fancy shapes?..................Do we have any clues or suggestions? My present take on fancies is to allow any depth so long as the stone is attractive and not fragile (too shallow). What do you all think????

Thanks..

 

[Rhino]

I hear dat Dave but with fancies there should be some guidelines regarding certain *extremes*. Ie. princess cuts with tables or depths at or around the 80% zone ... things like that.

 

[windowshopper]

I think we have established that "too deep" is a detriment to rounds somewhere 62% or more. NOW< how about fancy shapes?..................Do we have any clues or suggestions? My present take on fancies is to allow any depth so long as the stone is attractive and not fragile (too shallow). What do you all think????

Dave:
Keeping in mind I am just plain Jane consumer I don't agree- with that... i personally would never purchase a round diamond as I just don't care for them so I am of course partial to a couple of fancy cut shapes. However, the majority of fancies available (at least to me) seem medium to poorly cut. Too deep or too shallow. Mostly too deep. I would think there would/should be an ultra premium on well cut fancies (until they are universally cut better). As in--up there with round per carat.................

 

[oldminer]

Rhino:

It has been my constant belief that regardless of the shape, round and/or fancy, the inherent optical properties of diamond contol the very nature of light performance scores. We have pretty well defined tastes established from years of industry agreement that rounds over 62% or thereabouts don't fully meet the criteria for the super fine category of cutting. We have never had a consensus on fancy shapes. This is for good reason in some circumstances. Fancy shaped diamonds are generally cut from rough that gives a better financial outcome to the cutter to create a fancy instead of a round. Whatever the reason, it is a cutter's choice. Nothing outsells rounds in near colorless material, so cutting a fancy shape is a decision forced usually by the nature of the rough and occasionally by the outstanding orders a cutter might have for other shapes.

Most of the time fancy shaped diamonds are overly deep when compared to rounds. We accept this as rather natural because depth percentage only refers to width, but we generally have a longer length and the depth also relates to length if we want brilliancy. Squarish stones can be much more like rounds in depth and often are cut from rough that would otherwise be cut as a round anyway. Do we make one arbitrary rule squarish diamonds and another rule on depth % for diamonds that are longer than their width by a noticeable amount? Where do we make the percentage? 80% is way deep, I think. Will a reasonable consensus develop? Will light return begin to reduce before 80% is reached and end any disagreement? I don't know quite yet. I sure know and 80% depth diamond will not look its size compared to its weight....It ought not be graded Ideal, but that's my opinion, not an agreed fact so far.

I am not inclined to worry on the issue of shallow diamonds becuase we know light return will fail pretty fast as stones get shallow. My inclination is to use a rule such as no crown angle measured <29 or <30 degrees should be rated as Ideal, but I am not firmly committed to this, as yet.

 

[strmrdr]

Fancies:
asschers are the only ones Iv cared enough to do a lot of homework on.
asschers - my opinion is that 65% is the min and 75% is the max in my acceptable depth range.
Iv never seen a asscher under 65% that had the 10 mile deep look I crave and over 75% the size of the diamond suffers to much.
A high crown is must to bring some fire to the game.

All fancies: a girdle under med at any point is a serious downgrade. Brian @ whiteflash will disagree but I just cant buy into it.
Iv seen and heard of too many of the getting broke especially princess cuts.
Id rather give up some size for a safer girdle.
Any round with a girdle under thin is also questionable to me.

 

[Garry H (Cut Nut)]

Date: 12/4/2004 11:32:53 AM
Author: windowshopper

I think we have established that ''too deep'' is a detriment to rounds somewhere 62% or more. NOW< how about fancy shapes?..................Do we have any clues or suggestions? My present take on fancies is to allow any depth so long as the stone is attractive and not fragile (too shallow). What do you all think????

WS this stone has a 47% table and AGS will call it Ideal next year. So at 64.4% depth it is out of the race?
Even though in a ring setting it will stand very proud and show a lot more diamond from the side or oblique view?

The trouble with rules is they sometimes need to be broken when new stuff comes along.

 

[Garry H (Cut Nut)]

oops

 

[windowshopper]

Garry

I was talking about fancies..............and basically saying that well cut fancies should probably be a significant permium b/c so few of them are well cut