Princess: Why depth less than table

[moremoremore]

OK- I don''t mean to ask this same question again and again...especially when I know you can''t judge a fancy by the #s...but I am trying to narrow down a field so I can see two or three. Why is it than some suggest table less than depth? I do understand that with a smaller depth you have a better chance at having a good crown height....but what about when the stone is a 65 depth? I don''t think that means a table of say 69 is bad...right? But is it more or less likely to have a shallow crown? OK- I guess I''m asking once and for all- what is the/is there any relation b/t depth and table...someone used the parallel of a see-saw..but I just don''t get it! HELP!!!!

 

[moremoremore]

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[Nicrez]

Having a table of greater than the depth by a substantial amount will make the surface area of the stone much greater (bigger looking stone), but will also diminish the proper angles and depth needed to get the perfect reflection and refraction of light to maximize the brilliance and fire of the light entering the stone.

t can be easily seen on the examples people show of diamonds that are too shallow and diamonds that are too deep. The light needs to have the right room to reflect and refract, as it enters the diamond at certain angles, and when it hits the carbon, it will reflect and refract at specific angles. It's all difficult to calculate, but technically, "proper" angles can be achieved to be complimentary, and when the depth is too low and the table is out of proportion, these angles are not present, and what you have a is badly cut, glassy looking stone that doesn't sparkle as much as it could. a basic watse of a lot of money.

 

[moremoremore]

"Having a table of greater than the depth by a substantial amount will make the surface area of the stone much greater"

Thanks for the reply! I just don't get it though. Why should the depth have anything to do with surface area. .... And what happens when you have a 65 depth.....so a 69 table auto means a shallow crown...? I didn't think so....I do see that a really large table results in the shallow crown...but I still don't get how the heck that has anything do to with depth...!

 

[moremoremore]

I def do see a trend though....if you go to DBOF, GOG etc and look at the #s, the majority of the "ideal" stones have tables smaller than or around the depth....but I guess the light scope is there to see if that is true...I guess that's the point of not purchasing a diamond unseen! Duh!!

HEY- what the heck is the diff b/t the light scope and ideal scope??

 

[Nicrez]

Consider that all the angles HAVE to interact with each other. Open your hands and lie them flat as you can. Mock the angles of a crown angle, by keeping your hands apart a few inches. As you rotate your hands outward (where your fingertips delinate the table of the stone) you notice your table gets larger, so the angle your hands are moving makes the crown angles increase from 35 degrees to maybe 45 or greater...If the depth is to shallow and you have increases the table (thus the angles of the crown), you are effectively making the crown lower, but the depth will need to correspond with it.

It's somewhat simple geometry, where the angles correspond, and the crown angle and pavillion angle will correspond as well. By logic, you provide that the Crown height and pavillion depth will correspond, and as such table and depth will need to retain these critical correlations in angles and percents. Try drawing diamonds with big tables and low depth, and vice versa. The visual representation is much easier to see, I think...

 

[valeria101]

Good Q.

I didn't find a systematic explanation for this 'rule of thumb', but here is my compilation... by points:

To start with, I could consider the crown and pavilion as independent bodies (although this in not ok for all purposes). So... total depth is mostly detemined by the depth of the pavilion - the crown of princess cuts is about 10% of it anyway and cannot be too big because the crown angle does not get steeper than 40 degrees or flater than 25 (durability issues are inviked for these limits). The angle of the pavilion ca vary more and the sides correspondent to them are bigger - so the cut of the pavilion has the greatest impact on total weight.

Deeper stones are not very desirable - total depth determines the area of the stone (the area of the section through girdle) for each weight: the deeper the smaller for the same weight (and volume). This is simple geometry. So the depth of the pavilion is limited by this rule.

Why smaller tables are better ? For two reasons: it is better to have moderately steep pavilion angles to achieve better brilliance (se ray trace) and it is better to have larger minor pavilion facets to get more light dispersion (fire) off the face of the stone.

It is not the table itself that is the goal, but the pavilion angles. However, just try to draw a hypothetical section through the pavilion of a princess cut: a certain pavilion angle determies comletely the size of the table.

As in rounds, the pavilion angles are the main determinants of brilliance (so too deep pavilions are bad - depth being determined completely by the pavilion angles) and the pavilion angles is the strongest determinant of fire - so fiery princess cuts shoudl have a mderate table.


If the rule "get table less than pavilion" is applicable to any total depth (given the argument about fire), but it makes little sense for a 80% deep stone: 79% table on that would still not make it a fine cut - just a waste of material!

So? all these considerations first bring depth between a reasonable 65%-75%, then dictate "table < depth" so the table % becomes 62%-72% - keeping a couple of % points below table each time.

want more? - DiamCalc would bring precission to this story. In fact, it is much better to discuss this avoiding to take crown and pavilion measures separately. It makes more sense to work with a vertical section through the stone - so that the relation between table and total depth and between crown and pavilion angles become evident and one gets to use the minimum number of variables.

Hope this helps...

 

[valeria101]

Oh.. and since I like fiery diamonds, there is no such thing as too small a table for me; none is the best! (this does exist, examples could be the Leo Schachter princess (link) and better, the Spirit of Flanders quare

).

 

[valeria101]

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On 4/12/2004 11:05:50 AM moremoremore wrote:



HEY- what the heck is the diff b/t the light scope and ideal scope?? ----------------

You may want to read Garry's post on this (LINK) thread

The Firescope uses directional light so it achieves better definition (more nuances of red). Garry argues that this is done at a price of lost realism: directional lighting is not in your usual environment and the output of the tool errs from the principle of approximating human visual perception, considered by all these 'scopes. Conclusion? The Firescope gives more detail, up to yo to judge wether this is useful, and how academic you want to get about selecting a poor diamond...

 

[Nicrez]

Ana, I agree with you on the little to "no table" look! Some stones with huge table face up large, but when you see the reflection of the HUGE table, it's not a sparkle, but a big blinding light refelction... Any pictures of the Spirit of Flanders? Those are LOVELY!

That would be my next stone shape to get. A nice Flanders on a pendant... Hmmmm.... what's the difference between a Flanders Brilliant and the Spirit of Flanders?

 

[moremoremore]

thanks gals!!! So then, I think that when you have a princess with say a 65 depth, you STILL want to keep the table around 65 or less (hard to find!).... Now, I'm trying to narrow a field for in person comparison)...am I better off not calling in a 65 depth/67 table (even though that's still a good table "by the #s".... and going with the 70 depth, 68 table? I do understand about wanting not to go too deep b/c I don't want a really small stone... Thanks!

 

[moremoremore]

SO it's not just the #s....but the interplay of numbers.... a 64 depth and 68 table stone may be ideal by the numbers....but it's probably got a shallow crown despite its great number b/c of the interplay of numbers? So I'd be better going with the 70 depth and 70 table stone over that one? (these are all hypothetical stones).... Also, let me ask another question....what you would think about a 73 depth and 68 table.....would the crown be too large? Weight loss aside, is that considered too deep in comparison to the the table...or is that a good thing?

If you HAD to pick, just to call in some stones...
66 depth, 68 table
70 depth, 70 table
73 depth, 67 table

 

[Nicrez]

Me personally, I would get a stone that had a depth around 65-70%. And a table of 63-68% I would also prefer that the table be at least 1-3% LESS than depth. That would ensure that the crown would be large enough. Princesses aren't known for big crowns, and ARE known to have those larger, flatter crowns, so that's the cut style.

Again, I am not a princess fan for a few reasons, but the deth is by definition of the cut supposed to be LARGER than the table. I would get a sarin on it, and MOST IMPORTANTLY...SEE it. That always does the trick. If it takes your breath away, then it's a good stone.

 

[valeria101]

With no info on brilliance (some scope diagnostic) it's just gamble anyway.

Sure we can't find a stone with all required info in place with your parameters ?

 

[moremoremore]

well- here are a few I've seen...I can't get them all in though....I will be picking 2 or 3 and having the works performed....I'm not sure which vendor I'll be going with....I've been on EVERYONE'S site....some may even have these listed....other sites don't have exactly what I'm looking for, others do but they are so over-priced...The vendor will be able to get these in and cover with their policies.... SO, here goes- to make this easy- here are the depth table and mm only, they are pretty much equal in other respects all things considered (including price)...

2.24 ct, 72.9 depth, 68 table 7.08X7.09
I'm ok with the weight loss on this one b/c of its mms, carat weight and price

2.09 69.2 depth, 70 table 7.14X7.4

2.08 71 depth, 69 table 7.14 X 7.0

2.10 67.4 depth, 68 table, mm not sure but way over 7X7

2.02 66.9 depth, 68 table, mm not sure

 

[moremoremore]

i totally know it's a gamble...just wanna increase my odds!

 

[Nicrez]

The 2.08ct could be a good contender. Just because it's slightly over 70% eoth doesn't make it a dog at all. I have seen some well sparkling princesses slightly over, and I think if the angles on that one are good, it could be very nice.

I would of course suggest the tests be done, but again, I am in favor of depth being slightly higher than the table, even if it goes over the 70%...so the first one could be pretty nice, although there is a lot of top surface area lost to the magic carat weight in the girdle or pavillion... Your eye and the I-Scope could be the determining factors...Good luck!!!

 

[valeria101]

I surely hope that 2.10 turns out nice with all else going for it

. Otherwise, the 2.08 would be the runner-up.

Are you getting Iscopes on these? Just asking for the pavilion height will most likely not reduce the odds to get a less-than top brilliant stone. Some test of light return would !

 

[moremoremore]

I really want that 2.10 to be ok. I couldn't care less about depth being over 70...most are! Check out GOG....almost all!

So I think the 2.08 would be the runner up.... I also liked a 2.05 E Si1 68.2 X 69....7.16 X 6.95.... wonder why that one faces up so small considering it's depth and table?.... Also, saw this one which is WAY under budget....you can check out the cert....probably has no chance of being "eye clean"...? I'm all for a good si2...but I don't think this is one....especialy in light of that dirt cheap price...

http://www.whiteflash.com/princess/Princess-cut-diamond-487855.htm#

 

[moremoremore]

thank you guys for all your help!

 

[moremoremore]

OK- here is one more...Now, this stone sounds amazing....the only problem is the L to W. Now, I do love a rectangular look....in fact, you have an AMAZING radiant Ncrez and it looks like it has no bow-tie at all!

Lucky gal. I can absolutely not deal with ANY bow tie.... I just wonder if this will have one...

http://www.excellentdiamondcutters.com/details.asp?item=4825-35

 

[valeria101]

Gee! There's work on this thread...

#1: the piece at Whiteflash has great chances to hide it's inclusions forever from your site - they are small and scattered and not under the table (and this is the best scenario, according to what the 2D plot can show). You could regard the situation as if two VS2 stones have put their invisibly small inclusions together into one

This is a winner SI2! This could well be the best stone yet on your list, and getting the Iscope pic from Whiteflash sounds likely.

#2: princess cuts have two potential 'bowties'

The departure from a perfect square of the last stone is certainly not enough to become the crucial factor for a huge bowtie on the 'long' side. However, the cut of even perfectly square princess cuts may reveal all four 'bow ties' in all their beauty. They might not even be all bad (black on Iscope). Who knows?

I don' think there is a clear looser between the two. I suppose the stone at Whiteflash is a better buy. And I would surely love to see the respective red picture.

Hope this helps...