Why depth is not the opposite of spread in a fancy shape?

[Serg]

Date: 4/12/2010 1:18:35 PM
Author: oldminer
A Rectangular stone which measures 1:1.15 l/w has 15% more spread than an identical weight, and identical width SQUARE diamond which measures only 1:1 l/w. It would a matter of bulge, depth or both combined.


The same would not be true for pear, marq, oval, but only for rectangular shaped diamonds. These rounded configurations have variable outline curves and do not have spread based simply on length and width measures. It will have to be pixel counts of the girdle plane area or some other strategy to measure this area.

Dave,
Yes , you can say what if two diamonds with difference in L/W 15% have same weight then spreads have difference in 15%,
But in such case you need significantly change angles after you changed L/W to receive same weight . did you try do it without changing Depth?

it is not easy to receive same weight, same depth and difference in L/W in 15%. Could you give any real example? I did not check Emerald( to much combinations) , but I sure what it is not possible for classical Pear, Oval, Marquise,..
Lets discuss about real examples( with real girdle thickness) what consumer can find on market

 

[Karl_K]

Date: 4/12/2010 1:18:35 PM
Author: oldminer
A Rectangular stone which measures 1:1.15 l/w has 15% more spread than an identical weight, and identical width SQUARE diamond which measures only 1:1 l/w. It would a matter of bulge, depth or both combined.


The same would not be true for pear, marq, oval, but only for rectangular shaped diamonds. These rounded configurations have variable outline curves and do not have spread based simply on length and width measures. It will have to be pixel counts of the girdle plane area or some other strategy to measure this area.

identical weight, and identical width being the key words it would have 15% more spread with the same weight.
What are the odds of that actually happening in the real world however?

 

[diagem]

Date: 4/12/2010 4:34:17 AM
Author: Garry H (Cut Nut)

Date: 3/26/2010 11:36:22 AM
Author:Paul-Antwerp
This subject is a side-topic that came up in this thread, and probably deserves its own thread.

My point is that one simply cannot say that a deeper fancy shape means that the stone has less spread. This is because of two reasons.

First, in many fancy shapes, there is the length-to-width-ratio. The depth is calculated on the basis of the smallest diameter, the width. So, two stones might have the same depth, but a L/W-ratio that is 15% different. (1.75 is almost 17% more than 1.50). So, the same depth could easily have a difference in spread of 15%.
Second, most fancy shapes do not have just one main crown and pavilion angle. Any stone with multiple crown- and pavilion-angles can hide weight without affecting the spread. I have written articles about this effect in the PS-journal on princess-cuts, but it is even more obvious in step-cuts. Again here, a conservative estimate is that the same depth can hide another 15% in weight in the bulge of the pavilion and the crown.

Taking both into consideration, it shows that two fancy shapes with the same depth-percentage can differ up to 30% in spread.

Considering that the difference between a depth of 60% and one of 78% is also 30%, how can one then use depth to say something about spread?

Live long,

For ease of reading - Pauls first post in its original formating, but with the relevant part in bold - Sergey has posted it above.
Paul Sergey has raised some relevant issues related to your topic
Why depth is not the opposite of spread in a fancy shape?

I am not sure how to incorporate it into the Tutorial so that it is both simple for newbies, and accurate.

Here is some relevant proposed text:
Fancy shapes have a much wider range of face-up spread than rounds. Depth % is poorly correlated to spread as a result of specific fancy cut designs. Popular fancy shapes that have a smaller spread than rounds are Princess, Asscher and Cushion cuts, whereas Oval, Marquise and Pear cuts often spread larger.

Some of the in-house fancy cut diamond cuts listed in the Pricescope database have quantitative spread comparisons to that of a standard Tolkowsky round brilliant. For example, a 1.00ct Princess cut that has a -15% spread has the same surface area as an 0.85ct round.

Moderation is usually key with fancy shape spread. A very shallow stone will have great spread, but may have durability and brilliance issues. Excessive depth or pavilion bulge will have you paying for extra weight you won’t see face-up. Some fancy cuts require extra depth to optimize angles for better brilliance, fire, and scintillation.

There are a myriad of parameters that can make a beautiful fancy shape, so when you are comparing spread in fancies, remember that they are proportioned differently than round brilliants. Their spread factors are often a result of specific design and each stone should be evaluated for its particular merits.

Any suggestions to incorporate ''bugle'' are welcome. Perhaps this image could do it?

Impossible cut design..., face-up does not reflect profile (see my white circles)....

 

[Serg]

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[Serg]

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[oldminer]

My post was meant to clarify that the case "might" happen and that the statement when properly written makes perfect sense. Each particpant here is taking their own set of parameters to prove various things can relate to spread and I absolutely agree this is not a problem for which we can pick one solution. Bulge and depth both have the potential to change the spread. A bulge added to the girdle outline of a curved fancy also poses a change in spread which is not part of pavilion or crown bulge features already discussed.

I think we do agree that spread is the square mm area within the outline of the diamond measured at the plane of the girdle. Beyond that, we all see weaknesses in how to describe it when comparing non-identical diamonds. And, most diamonds are NOT Identical to one another.

 

[Serg]

Date: 4/12/2010 1:43:40 PM
Author: Serg

Date: 4/12/2010 1:18:35 PM

Author: oldminer

A Rectangular stone which measures 1:1.15 l/w has 15% more spread than an identical weight, and identical width SQUARE diamond which measures only 1:1 l/w. It would a matter of bulge, depth or both combined.



The same would not be true for pear, marq, oval, but only for rectangular shaped diamonds. These rounded configurations have variable outline curves and do not have spread based simply on length and width measures. It will have to be pixel counts of the girdle plane area or some other strategy to measure this area.

Dave,

Yes , you can say what if two diamonds with difference in L/W 15% have same weight then spreads have difference in 15%,

But in such case you need significantly change angles after you changed L/W to receive same weight . did you try do it without changing Depth?


it is not easy to receive same weight, same depth and difference in L/W in 15%. Could you give any real example? I did not check Emerald( to much combinations) , but I sure what it is not possible for classical Pear, Oval, Marquise,..

Lets discuss about real examples( with real girdle thickness) what consumer can find on market


Sergey Sivovolenko
CEO OctoNus

Dave ,

and if you do it for cut as Emerald or cuts with Moon facets , it has strong connection to second Paul statement

"Second, most fancy shapes do not have just one main crown and pavilion angle. Any stone with multiple crown- and pavilion-angles can hide weight without affecting the spread. I have written articles about this effect in the PS-journal on princess-cuts, but it is even more obvious in step-cuts. Again here, a conservative estimate is that the same depth can hide another 15% in weight in the bulge of the pavilion and the crown. "

what is correct of course .
But what is first Paul statement in such case

"First, in many fancy shapes, there is the length-to-width-ratio. The depth is calculated on the basis of the smallest diameter, the width. So, two stones might have the same depth, but a L/W-ratio that is 15% different. (1.75 is almost 17% more than 1.50). So, the same depth could easily have a difference in spread of 15%."??

 

[Serg]

Date: 4/12/2010 2:01:05 PM
Author: oldminer
My post was meant to clarify that the case 'might' happen and that the statement when properly written makes perfect sense. Each particpant here is taking their own set of parameters to prove various things can relate to spread and I absolutely agree this is not a problem for which we can pick one solution. Bulge and depth both have the potential to change the spread. A bulge added to the girdle outline of a curved fancy also poses a change in spread which is not part of pavilion or crown bulge features already discussed.


I think we do agree that spread is the square mm area within the outline of the diamond measured at the plane of the girdle. Beyond that, we all see weaknesses in how to describe it when comparing non-identical diamonds. And, most diamonds are NOT Identical to one another.

re:I think we do agree that spread is the square mm area within the outline of the diamond measured at the plane of the girdle.

Dave, I am disagree. I do not know such Spread definition and has not any idea how it could works without mass.

 

[oldminer]

Sergey:

I think we are attempting to define "spread" for ourselves as there are currently only opinions and arguments over the meaning of the word. We must define it properly and clearly before we can solve the issue with good reasoning.

Diamonds have a highly consistent specific gravity and equal volumes of diamond cleary are consistent in weight. To my mind, spread relates to how much area is within the outline of the girdle plane. If two or more diamonds, of equal weight, are compared, no matter what their outline shapes are, the one diamond with more square mm area within the girdle outline''s plane has more spread. Don''t you clearly agree with this logical scenario?

This would not allow comparison of different weight diamonds, but it is my belief shoppers want "comparison tools". They don''t need descriptions of spread when looking at individual diamonds nearly as much as they need such tools for comparison of diamond''s visual sizes to one another. They could readily compare a 1.01ct round with a 1.03ct round for spread as the weight would be close enough for some meaning to be found with a comparison although not a perfect one.

Another issue is that pears and marquise shapes nearly always have more spread than round or rectangular diamonds for a given weight. However, I doubt many shoppers want to compare a marquise to an emerald cut very often. Consumers rarely would be shopping for such different types of diamond looks at the same time and wishing to make comparisons. Comparisons of those types would be pretty much a waste of time with all the other factors to consider.

 

[Serg]

Date: 4/12/2010 2:46:38 PM
Author: oldminer
Sergey:


I think we are attempting to define ''spread'' for ourselves as there are currently only opinions and arguments over the meaning of the word. We must define it properly and clearly before we can solve the issue with good reasoning.


Diamonds have a highly consistent specific gravity and equal volumes of diamond cleary are consistent in weight. To my mind, spread relates to how much area is within the outline of the girdle plane. If two or more diamonds, of equal weight, are compared, no matter what their outline shapes are, the one diamond with more square mm area within the girdle outline''s plane has more spread. Don''t you clearly agree with this logical scenario?


This would not allow comparison of different weight diamonds, but it is my belief shoppers want ''comparison tools''. They don''t need descriptions of spread when looking at individual diamonds nearly as much as they need such tools for comparison of diamond''s visual sizes to one another. They could readily compare a 1.01ct round with a 1.03ct round for spread as the weight would be close enough for some meaning to be found with a comparison although not a perfect one.


Another issue is that pears and marquise shapes nearly always have more spread than round or rectangular diamonds for a given weight. However, I doubt many shoppers want to compare a marquise to an emerald cut very often. Consumers rarely would be shopping for such different types of diamond looks at the same time and wishing to make comparisons. Comparisons of those types would be pretty much a waste of time with all the other factors to consider.

Dave,

I prefer use OctoNus spread definition
http://www.octonus.com/oct/products/3dcalc/standard/param17.phtml


"The spread is parameter showing the difference between the weight of the given diamond and the weight of the "standard diamond". The "standard diamond" has the same area as the given diamond but Tolkowsky proportions with the medium girdle thickness. The spread parameter tells you if your diamond looks more or less massive than it really is."

Because:
1) It works well for any cuts and any mass
2) It had been implemented in Diamcalc since May 2002 year ( almost 8 years ago)
http://www.octonus.com/oct/products/3dcalc/standard/history.phtml

I happy consider better options. Could you please explain what problem you see in OctoNus spread definition? Why do you prefer find different spread definition ?

 

[oldminer]

I would agree that the Octonus method is highly scientific and would work if consumers have interest in how any shape compares to a well made Tolkowsky round diamond. I suppose they could measure two fancy cuts for comparison to your Tolkowsky round standard and also know which fancy shape had more spread than the other. It seems complex, but you are way more "edjumacated" than I am in these mathmatical matters.
The end result would be the same knowledge that one diamond looks larger for its weight than the other looks for its weight. It would take weight differences into account better than my simpler method.

The way I conceive of making meaningful comparisons of similar shape diamonds directly with one another has an easier explanation curve for consumers, I also think it could work well with the calculation software already present in Octonus although it would take more work on your part to get it to act in the way I propose.

What is simply most desired by ordinary users would be just the square mm area of the girdle plane of a measured diamond. The rest could be figured out by most consumers without any math skill or broader understanding.

 

[Garry H (Cut Nut)]

Thankns CCL and Sergey

Date: 4/12/2010 10:40:28 AM
Author: Serg
CCL, Garry


there are two correct sentences for Garry example:

''Some of the in-house fancy cut diamond cuts listed in the Pricescope database have quantitative spread comparisons to that of a standard Tolkowsky round brilliant. For example, a 1.00ct Princess cut that has a -0.13ct spread has the same surface area as an 0.87ct round.''

or

''Some of the in-house fancy cut diamond cuts listed in the Pricescope database have quantitative spread comparisons to that of a standard Tolkowsky round brilliant. For example, a 1.00ct Princess cut that has a -15% spread has the same surface area as an 0.87ct round. ''

15%*0.87ct=0.13ct

 

[diagem]

Date: 4/12/2010 3:34:53 PM
Author: oldminer
I would agree that the Octonus method is highly scientific and would work if consumers have interest in how any shape compares to a well made Tolkowsky round diamond. I suppose they could measure two fancy cuts for comparison to your Tolkowsky round standard and also know which fancy shape had more spread than the other. It seems complex, but you are way more ''edjumacated'' than I am in these mathmatical matters.
The end result would be the same knowledge that one diamond looks larger for its weight than the other looks for its weight. It would take weight differences into account better than my simpler method.

The way I conceive of making meaningful comparisons of similar shape diamonds directly with one another has an easier explanation curve for consumers, I also think it could work well with the calculation software already present in Octonus although it would take more work on your part to get it to act in the way I propose.

What is simply most desired by ordinary users would be just the square mm area of the girdle plane of a measured diamond. The rest could be figured out by most consumers without any math skill or broader understanding.

I mostly tend to lean with Dave here as I dont think its such a scientific issue!
But cant see tech PS''ers leaving the science out...

I just wonder..., if already technical..., then CH (vertical spread) is inevitable.

 

[ChunkyCushionLover]

Date: 4/12/2010 3:34:53 PM
Author: oldminer
I would agree that the Octonus method is highly scientific and would work if consumers have interest in how any shape compares to a well made Tolkowsky round diamond. I suppose they could measure two fancy cuts for comparison to your Tolkowsky round standard and also know which fancy shape had more spread than the other. It seems complex, but you are way more ''edjumacated'' than I am in these mathmatical matters.
The end result would be the same knowledge that one diamond looks larger for its weight than the other looks for its weight. It would take weight differences into account better than my simpler method.

The way I conceive of making meaningful comparisons of similar shape diamonds directly with one another has an easier explanation curve for consumers, I also think it could work well with the calculation software already present in Octonus although it would take more work on your part to get it to act in the way I propose.

What is simply most desired by ordinary users would be just the square mm area of the girdle plane of a measured diamond. The rest could be figured out by most consumers without any math skill or broader understanding.

I agree.


To me:
Faceup Spread is equivalent to Surface Area of Girdle Plain (Carat Weight is not included)

Octonus Spread works well when you are comparing diamonds of the exact same weight then a direct comaprison of the spread +/- % is directly comparable, if however the weights are a little different than surface area would be needed. Serg expalined to me earlier in the theread the method I would need to use to convert Octonus spread to actual surface area:

1) Get spread difference in % from Diamcalc
2) Get diameter of Tolk Round using the propotions listed for Ideal Tolk Round http://www.octonus.ru/oct/products/3dcalc/standard/param17.phtml , lock all parameters except diameter and change carat weight to the weight of the fancy cut diamond to get the diameter of a Tolk Round with the same carat weight as the fancy shape.
3) Use Pie*(Diameter/2)*(Diameter/2) to calculate surface area of that ideal tolk round with the same weight as the fancy shape
4) Multiple Ideal Spread Of Tolk Round * Spread difference to get the actual surface area of the Fancy Shape

Thats multiple steps, it would be a lot easier if faceup surface area was included as an output instead of having to do all that.

 

[ChunkyCushionLover]

Date: 4/12/2010 4:06:46 PM
Author: Garry H (Cut Nut)
Thankns CCL and Sergey

Date: 4/12/2010 10:40:28 AM
Author: Serg
CCL, Garry


there are two correct sentences for Garry example:

'Some of the in-house fancy cut diamond cuts listed in the Pricescope database have quantitative spread comparisons to that of a standard Tolkowsky round brilliant. For example, a 1.00ct Princess cut that has a -0.13ct spread has the same surface area as an 0.87ct round.'

or

'Some of the in-house fancy cut diamond cuts listed in the Pricescope database have quantitative spread comparisons to that of a standard Tolkowsky round brilliant. For example, a 1.00ct Princess cut that has a -15% spread has the same surface area as an 0.87ct round. '

15%*0.87ct=0.13ct

Gary,

I haven't purchased Diamcalc yet so I hope someone will answer this for me:

What is the Diameter in mm.

1) 0.85 ct round stone with ideal tolk parameters (if it was 1ct it would have a diameter of 6.47mm).?
2) 0.87 ct with ideal tolk parameters?
3) 0.85ct round with +15% spread?
4) 0.87ct round with +15% spread?
5) 1 ct round with -15% spread?

What are the Length and Width of that princess with -15% spread?

Thanks,
CCL

 

[Serg]

CCL,

I think you mixed two phenomena : Spread and Size( what diamond looks bigger)
please separate these issues . Size( area ) is not Spread. Spread is not size( area)
when you speak about "area" please do not use term "spread"
you posts are quite misleading because when you write"spread" you mean "area"
I do not see any sense rename "area" into "spread" in diamond industry

 

[ChunkyCushionLover]

Date: 4/12/2010 9:31:52 PM
Author: Serg
CCL,

I think you mixed two phenomena : Spread and Size( what diamond looks bigger)
please separate these issues . Size( area ) is not Spread. Spread is not size( area)
when you speak about ''area'' please do not use term ''spread''
you posts are quite misleading because when you write''spread'' you mean ''area''
I do not see any sense rename ''area'' into ''spread'' in diamond industry

I want to know at least one method for compariing faceup size (which one looks bigger) of two diamonds surface area is one such method (with limitations).

I agree with Old Miner that a consumer that wants to compare the faceup size of two diamonds would find surface area more useful and they would not necessarily find it useful to use as a reference for spread a Tolk Round as defined in DiamCalc.

Call it (Insert Name) not spread if you wish, but I still don''t see everyone here agreeing on the definition of spread, but we all should agree on what surface area of the girdle plain means.

 

[Garry H (Cut Nut)]

Date: 4/13/2010 2:01:50 AM
Author: ChunkyCushionLover

Date: 4/12/2010 9:31:52 PM
Author: Serg
CCL,

I think you mixed two phenomena : Spread and Size( what diamond looks bigger)
please separate these issues . Size( area ) is not Spread. Spread is not size( area)
when you speak about ''area'' please do not use term ''spread''
you posts are quite misleading because when you write''spread'' you mean ''area''
I do not see any sense rename ''area'' into ''spread'' in diamond industry

I want to know at least one method for compariing faceup size (which one looks bigger) of two diamonds surface area is one such method (with limitations).

I agree with Old Miner that a consumer that wants to compare the faceup size of two diamonds would find surface area more useful and they would not necessarily find it useful to use as a reference for spread a Tolk Round as defined in DiamCalc.

Call it (Insert Name) not spread if you wish, but I still don''t see everyone here agreeing on the definition of spread, but we all should agree on what surface area of the girdle plain means.

CCL why not make it $''s per square millimeter.

The comparison to a standard round is the only practical industry standard. Everyone knows what a round is and knowing that this or that stone is bigger in spread or smaller in spread than a round and by how much is easily understandable. It works for all shapes including round diamonds themselves.
Knowing this diamond for $5,000 is 32mm sq and this one for $10,000 is 41mm sq is not useful.

Already we have many posts from consumers who ask "will I see the difference between a 6.1mm and a 6.2mm diamond". How will surface area help them? Who will explain even what "surface area of the girdle plain" means?

 

[Serg]

Date: 4/13/2010 2:01:50 AM
Author: ChunkyCushionLover

Date: 4/12/2010 9:31:52 PM

Author: Serg

CCL,


I think you mixed two phenomena : Spread and Size( what diamond looks bigger)

please separate these issues . Size( area ) is not Spread. Spread is not size( area)

when you speak about ''area'' please do not use term ''spread''

you posts are quite misleading because when you write''spread'' you mean ''area''

I do not see any sense rename ''area'' into ''spread'' in diamond industry

I want to know at least one method for compariing faceup size (which one looks bigger) of two diamonds surface area is one such method (with limitations).



I agree with Old Miner that a consumer that wants to compare the faceup size of two diamonds would find surface area more useful and they would not necessarily find it useful to use as a reference for spread a Tolk Round as defined in DiamCalc.


Call it (Insert Name) not spread if you wish, but I still don''t see everyone here agreeing on the definition of spread, but we all should agree on what surface area of the girdle plain means.

CCL,

Spread is parameter to measure how is effective mass had been used to create visual diamond size( area)

You can not use parameter area/mass for this task. Is reason clear?
Just check it for 1ct and 10ct diamonds with exactly same proportions.
Same reason will block correct comparison for diamonds even with similar masses.

Very often easy approach can not give correct results.
You can use area only for answer which diamond looks bigger. Spread gives other type information , it helps you do more smart choice


Please give and explain your choice between 0.8ct round 6mm and 0.9ct round 6.3mm

 

[ChunkyCushionLover]

Date: 4/13/2010 2:49:05 AM
Author: Garry H (Cut Nut)

Date: 4/13/2010 2:01:50 AM
Author: ChunkyCushionLover

Date: 4/12/2010 9:31:52 PM
Author: Serg
CCL,

I think you mixed two phenomena : Spread and Size( what diamond looks bigger)
please separate these issues . Size( area ) is not Spread. Spread is not size( area)
when you speak about ''area'' please do not use term ''spread''
you posts are quite misleading because when you write''spread'' you mean ''area''
I do not see any sense rename ''area'' into ''spread'' in diamond industry

I want to know at least one method for compariing faceup size (which one looks bigger) of two diamonds surface area is one such method (with limitations).

I agree with Old Miner that a consumer that wants to compare the faceup size of two diamonds would find surface area more useful and they would not necessarily find it useful to use as a reference for spread a Tolk Round as defined in DiamCalc.

Call it (Insert Name) not spread if you wish, but I still don''t see everyone here agreeing on the definition of spread, but we all should agree on what surface area of the girdle plain means.

CCL why not make it $''s per square millimeter.

The comparison to a standard round is the only practical industry standard. Everyone knows what a round is and knowing that this or that stone is bigger in spread or smaller in spread than a round and by how much is easily understandable. It works for all shapes including round diamonds themselves.
Knowing this diamond for $5,000 is 32mm sq and this one for $10,000 is 41mm sq is not useful.

Already we have many posts from consumers who ask ''will I see the difference between a 6.1mm and a 6.2mm diamond''. How will surface area help them? Who will explain even what ''surface area of the girdle plain'' means?

So back to my original question than:

0.87 Ct with +15% spread = 1 Ct Reference Round right?
Does 1 Carart with -15% spread = 0.85 Ct Reference Round or is it llike I thought Weight<0.85?

 

[ChunkyCushionLover]

Date: 4/13/2010 3:15:46 AM
Author: Serg

Date: 4/13/2010 2:01:50 AM
Author: ChunkyCushionLover

Date: 4/12/2010 9:31:52 PM

Author: Serg

CCL,


I think you mixed two phenomena : Spread and Size( what diamond looks bigger)

please separate these issues . Size( area ) is not Spread. Spread is not size( area)

when you speak about ''area'' please do not use term ''spread''

you posts are quite misleading because when you write''spread'' you mean ''area''

I do not see any sense rename ''area'' into ''spread'' in diamond industry

I want to know at least one method for compariing faceup size (which one looks bigger) of two diamonds surface area is one such method (with limitations).



I agree with Old Miner that a consumer that wants to compare the faceup size of two diamonds would find surface area more useful and they would not necessarily find it useful to use as a reference for spread a Tolk Round as defined in DiamCalc.


Call it (Insert Name) not spread if you wish, but I still don''t see everyone here agreeing on the definition of spread, but we all should agree on what surface area of the girdle plain means.

CCL,

Spread is parameter to measure how is effective mass had been used to create visual diamond size( area)

You can not use parameter area/mass for this task. Is reason clear?
Just check it for 1ct and 10ct diamonds with exactly same proportions.
Same reason will block correct comparison for diamonds even with similar masses.

Very often easy approach can not give correct results.
You can use area only for answer which diamond looks bigger. Spread gives other type information , it helps you do more smart choice


Please give and explain your choice between 0.8ct round 6mm and 0.9ct round 6.3mm

Octonus spread doesn''t give me any information useful for comparing size of different weight diamonds. If weights are different than even comparing two different designs with two different weights you cannot directly take the difference of Octonus Spread.

Garry used 6.1mm and 6.2mm example:

0.85Ct Reference Tolk ~ 6.1mm (Octonus Spread = 0%)
0.9 Ct Reference Tolk ~ 6.2mm (Octonue Spread = 0%)

Difference in Octonus spread = 0% therefore it doesn''t give any information about the size difference of the two just that both have same faceup size as reference tolk round with the same weight.
--------------

But the consumer may want to compare two diamonds with slightly different weights and designs and determine which one will have a larger faceup size

.

 

[Garry H (Cut Nut)]

Date: 4/13/2010 3:58:45 AM
Author: ChunkyCushionLover


So back to my original question than:

0.87 Ct with +15% spread = 1 Ct Reference Round right? - no it = 6.53, not 6.47mm - +13% spread = about 6.47mm

Does 1 Carart with -15% spread = 0.85 Ct Reference Round or is it llike I thought Weight<0.85? no, 1ct with -15% spread = 1.15ct, but 1ct with -15% spread is 0.13ct smaller in spread so the same size as 0.87ct

 

[Serg]

Date: 4/13/2010 4:16:13 AM
Author: ChunkyCushionLover

Date: 4/13/2010 3:15:46 AM

Author: Serg

Date: 4/13/2010 2:01:50 AM

Author: ChunkyCushionLover

Date: 4/12/2010 9:31:52 PM


Author: Serg


CCL,



I think you mixed two phenomena : Spread and Size( what diamond looks bigger)


please separate these issues . Size( area ) is not Spread. Spread is not size( area)


when you speak about ''area'' please do not use term ''spread''


you posts are quite misleading because when you write''spread'' you mean ''area''


I do not see any sense rename ''area'' into ''spread'' in diamond industry

I want to know at least one method for compariing faceup size (which one looks bigger) of two diamonds surface area is one such method (with limitations).




I agree with Old Miner that a consumer that wants to compare the faceup size of two diamonds would find surface area more useful and they would not necessarily find it useful to use as a reference for spread a Tolk Round as defined in DiamCalc.



Call it (Insert Name) not spread if you wish, but I still don''t see everyone here agreeing on the definition of spread, but we all should agree on what surface area of the girdle plain means.

CCL,


Spread is parameter to measure how is effective mass had been used to create visual diamond size( area)


You can not use parameter area/mass for this task. Is reason clear?

Just check it for 1ct and 10ct diamonds with exactly same proportions.

Same reason will block correct comparison for diamonds even with similar masses.


Very often easy approach can not give correct results.

You can use area only for answer which diamond looks bigger. Spread gives other type information , it helps you do more smart choice



Please give and explain your choice between 0.8ct round 6mm and 0.9ct round 6.3mm

Octonus spread doesn''t give me any information useful for comparing size of different weight diamonds. If weights are different than even comparing two different designs with two different weights you cannot directly take the difference of Octonus Spread.


Garry used 6.1mm and 6.2mm example:


0.85Ct Reference Tolk ~ 6.1mm (Octonus Spread = 0%)

0.9 Ct Reference Tolk ~ 6.2mm (Octonue Spread = 0%)


Difference in Octonus spread = 0% therefore it doesn''t give any information about the size difference of the two just that both have same faceup size as reference tolk round with the same weight.

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But the consumer may want to compare two diamonds with slightly different weights and designs and determine which one will have a larger faceup size

.

CCL,

Please give and explain your choice between 0.8ct round 6mm and 0.9ct round 6.3mm

I never saw result your method on real example.
After you publish your results and explanations, I will publish Octonus Spread for same diamonds

 

[oldminer]

I think it is clearly apparent that consumers and pro-sumers would find the square area of any shape diamond a very good number to have when shopping, as it clearly responds to the very common question: "Which diamond will look larger?"
If two diamonds happen to be the same or very similar weight, it also is would give them a good clue or a true answer, at identical weight, of which diamond has more "spread". This sqaure mm area of the girdle plane outline should be a relatively easy parameter to report on any shape diamond.

Again, defining the word "spread" has yet to be agreed upon. I see my method as important when questioning visual size/weight when comparing similar weight diamonds of any shape. I don''t see it as so important a term for a stand alone purpose when describing a single diamond although comparing such a stone to an idealized Tolkowsky is a consistent methodology for those times when that kind of comparison or cutting advice might be needed by a cutting house or a marketing firm.

 

[Garry H (Cut Nut)]

Date: 4/13/2010 8:52:34 AM
Author: oldminer
I think it is clearly apparent that consumers and pro-sumers would find the square area of any shape diamond a very good number to have when shopping, as it clearly responds to the very common question: ''Which diamond will look larger?''
If two diamonds happen to be the same or very similar weight, it also is would give them a good clue or a true answer, at identical weight, of which diamond has more ''spread''. This sqaure mm area of the girdle plane outline should be a relatively easy parameter to report on any shape diamond.

Again, defining the word ''spread'' has yet to be agreed upon. I see my method as important when questioning visual size/weight when comparing similar weight diamonds of any shape. I don''t see it as so important a term for a stand alone purpose when describing a single diamond although comparing such a stone to an idealized Tolkowsky is a consistent methodology for those times when that kind of comparison or cutting advice might be needed by a cutting house or a marketing firm.

Dave I can not understand what is difficult about a simple comparitive system?

And who can police sq mm in stones with rounded corners etc?
I can assure you it will not be implimented in DiamCalc because we believe in one system that both manufacturers (can use for optimisation) and consumers can use (for protection).

 

[Serg]

Date: 4/13/2010 8:52:34 AM
Author: oldminer
I think it is clearly apparent that consumers and pro-sumers would find the square area of any shape diamond a very good number to have when shopping, as it clearly responds to the very common question: ''Which diamond will look larger?''

If two diamonds happen to be the same or very similar weight, it also is would give them a good clue or a true answer, at identical weight, of which diamond has more ''spread''. This sqaure mm area of the girdle plane outline should be a relatively easy parameter to report on any shape diamond.


Again, defining the word ''spread'' has yet to be agreed upon. I see my method as important when questioning visual size/weight when comparing similar weight diamonds of any shape. I don''t see it as so important a term for a stand alone purpose when describing a single diamond although comparing such a stone to an idealized Tolkowsky is a consistent methodology for those times when that kind of comparison or cutting advice might be needed by a cutting house or a marketing firm.

Dave,
square area could be helpful in reports. It is not issue.
main my statements is what method SquareArea/weight is quite misleading( as Spread method) and will give wrong answer very often even if weights are similar.

Please use this method for my example " 0.8ct round 6mm and 0.9ct round 6.3mm" and give your decision which diamond has bigger spread.

 

[Serg]

Dave,

Should 1ct and 2ct round cut diamonds with exact same proportions have Same Spread?

 

[Karl_K]

Date: 4/13/2010 9:25:00 AM
Author: Serg
Dave,


Should 1ct and 2ct round cut diamonds with exact same proportions have Same Spread?

square mm per ct solves that problem.

 

[Serg]

Date: 4/13/2010 11:01:35 AM
Author: Karl_K

Date: 4/13/2010 9:25:00 AM

Author: Serg

Dave,



Should 1ct and 2ct round cut diamonds with exact same proportions have Same Spread?

square mm per ct solves that problem.

Karl,

How did you receive such result? Did you check it?

what is square area ratio between 1ct and 2ct round diamonds?( between diamonds with diameters 6.46 and 8.14 mm for example)?

 

[Karl_K]

Date: 4/13/2010 11:13:05 AM
Author: Serg

Date: 4/13/2010 11:01:35 AM

Author: Karl_K

Date: 4/13/2010 9:25:00 AM


Author: Serg


Dave,




Should 1ct and 2ct round cut diamonds with exact same proportions have Same Spread?

square mm per ct solves that problem.

Karl,


How did you receive such result? Did you check it?


what is square area ratio between 1ct and 2ct round diamonds?( between diamonds with diameters 6.46 and 8.14 mm for example)?

The 1ct has more spread per ct which is a fact...