Which diamond would have more face up surface area?

[strmrdr]

diamond A
diamond B
the same because they are both 6mm
............
Diamond A

 

[strmrdr]

diamond B

 

[Regular Guy]

same?

 

[valeria101]

What''s the point ?

 

[Regular Guy]

Date: 11/10/2005 9:48:49 AM
Author: valeria101
What''s the point ?

Storm will answer, but I''m betting he''s picking a fight on the value of the spread index on the new database...which is just trying to creatively push the limited data as much as you can, I think.

 

[valeria101]

Date: 11/10/2005 9:52:55 AM
Author: Regular Guy

Date: 11/10/2005 9:48:49 AM
Author: valeria101
What''s the point ?

Storm will answer, but I''m betting he''s picking a fight on the value of the spread index on the new database...which is just trying to creatively push the limited data as much as you can, I think.

Thanks. I found the thing.

Well, I don''t like them flat either, but girdle section area still sounds more like ''size'' than the unfolded surface (how do you call this in English???).

It is not hard to get that index given crown height... but that''s not on the cert. And even if it was, I find it hard to agree with the logic.

If I could balance brilliance and size that would make sense. But the high crown unrelated to brilliance - why would that be a good thing?

 

[valeria101]

Anyway, I must have posted this before... just to say it better that yes, I should admit that Strm has a point to make

 

[Patty]

6 mms is 6 mms.

 

[oldminer]

Face up surface area to weight ratio may prove a useful tool in comparing various similar diamonds. People do want to know which one looks larger. They will also want to know if one diamond offers more bang for the buck wehn all other measures seem rather equal.

The best performaing diamonds will probalby lie within certain wide ranges of surace area with weight ratio. We just don''t have sufficient data yet to know what this calculation may mean or not mean. It sounds like a logical thing to investigate and that''s what we are doing right now.

 

[valeria101]

Date: 11/10/2005 2:32:06 PM
Author: oldminer

Face up surface area to weight ratio may prove a useful tool in comparing various similar diamonds.

There is a small catch - just a bit of random math. I don''t know if it applies to the problem, but it sounds correct.

At least for rounds and square diamonds, surface grown with weight at a decreasing rate. Which means that lighter diamonds would always have better surface/weight ratios. So the indicator is useful to compare diamonds of very similar weight - which is probably the intended use anyway, but over a wider range it starts saying that smaller diamonds somehow have better spread. (say, 0.75 cts versus 1 ct, if anyone cared to compare them for size). Which seems counterintuitive.

And ''similar weight'' may need to be very close. For weights around 1 carat and below, even weight differences of about 10 pts may reverse the spread score to rank the slightly lighter diamond better than the slightly larger one.

To look for replacements for a diamond with the same weight and size/weight would work, of course. To choose between one 1.3cts and 1.5cts based on this measure, not quite.

I hope this is not out of place to mention...

 

[oldminer]

Strmrdr;

The flat top diamond looks as if it would weigh less than the more acceptably cut diamond. Is this part of what you are getting at?

 

[strmrdr]

Date: 11/10/2005 3:29:37 PM
Author: oldminer
Strmrdr;


The flat top diamond looks as if it would weigh less than the more acceptably cut diamond. Is this part of what you are getting at?

No my point is that surface area is not a function of diameter alone but crown height enters the picture also.

If you want to use girdle plane area which would be a 6mm circle then ok but it isn't the same as surface area.

The high crown diamond has more visible diamond surface area when looked at from the top.

if you molded plastic over the crowns of both then flattened out the plastic the one for the higher crown diamond will be larger.
Even though that added area is a slope its still visible surface area.

 

[Garry H (Cut Nut)]

I agree with you Storm, and it was part of the discussion with Leonid about the new in house damond spread factor. But we decided it was too hard.

If you do a search you will see I have been on this wavelength for some years.
https://www.pricescope.com/community/threads/is-this-a-good-price.2615/=
I have an even more important concept that Sergey could program into DiamCalc if we could make some rules for him. This example that everyone who meets me has seen (I carry them in my pocket always) shows how much smaller diamonds with upper girdle leakage look - especially once they are dirty.

DiamCalc could estimate this effect. I think it is another of the important variables for all cuts.

Also AGS are considering weighting their grading system (behind the scenes comutation stuff from the scanned stone) to include the results of the light return etc through rotation bsaed on weighted surface area.

 

[oldminer]

In every post I have made I have used visual, face-up surface area, and STRMRDR has made me see that what I said might have been confusing. His use of the area of the girdle plane is what I meant all along, NOT the flattened out surface of the area of the crown. Probably some people did understand all along what I meant, but it is not obvious that some didn't. I'm glad StrmrDr made it far clearer.

It is my contention that the area inside the plane of the girdle in relation to carat weight, whether a ratio or a percentage, will show which diamond to have more or less visual size than another of the same weight. It will prove a good comparision tool. No doubt, diamonds that are overly large, too spready, will get to a point where light performance suffers. The same with overly deep or bulging pavilion diamonds. Within the high performance range, the ratio of girdle plane area to weight will assist people in selecting a diamond that they prefer.

 

[strmrdr]

Dave,
Hopefully this will clear it up and the term surface area will be dropped when referring to it.

My frustration stems from liking things black and white and wrapped in nice little boxes on a chart :}
The gray areas in the diamond world drive me nuts at times.
Adding another gray area by improper terminalogy in this case was driving me to distraction.
I havent commented on it in the past because it is a work in progress while its being presented as a final product in the new search.

 

[strmrdr]

Date: 11/11/2005 1:42:16 AM
Author: Garry H (Cut Nut)

I agree with you Storm, and it was part of the discussion with Leonid about the new in house damond spread factor. But we decided it was too hard.

If you do a search you will see I have been on this wavelength for some years.

https://www.pricescope.com/community/threads/is-this-a-good-price.2615/=

I have an even more important concept that Sergey could program into DiamCalc if we could make some rules for him. This example that everyone who meets me has seen (I carry them in my pocket always) shows how much smaller diamonds with upper girdle leakage look - especially once they are dirty.


DiamCalc could estimate this effect. I think it is another of the important variables for all cuts.


Also AGS are considering weighting their grading system (behind the scenes comutation stuff from the scanned stone) to include the results of the light return etc through rotation bsaed on weighted surface area.

Kewl you agree.
Weighted light return area would be a way kewl concept to explore.

As I asked in the other thread:
"Would they pick a larger stone cut like your bad cz or a smaller one cut like your good cz that looks just as big?"

Weighted light return area would answer that problem.