Do shallow stones always face up larger than deeper stones?

[Rockdiamond]

An interesting discussion developed in another thread.
Common sense would dictate depth and spread are closely related- and in fact they are.
But what about anomalies?
Are shallow stones always "flat" looking?
Are deep stones always dark in the middle?

The answer to both hypothetical questions is no.

Here's a few plots that show how an open culet, and/or different placement of the girdle affect PA/CA. This shows that depth percentage is not always providing the results we expect.

Below, a more shallow antique style- smaller culet



Below a deeper antique style- large culet- we can see that if we extended the pavilion to close the culet the stone would be 10-20% deeper




Below a more "traditional" girdle placement on a radiant cut


These three plots help illustrate how depth percentage does not always follow a logical progression related to spread.

 

[Karl_K]

Re: Do shallow stones always face up larger than deeper ston

"Common sense would dictate depth and spread are closely related"

Then common sense would be wrong at times.
With a RB yes with fancies no!

 

[Rockdiamond]

Re: Do shallow stones always face up larger than deeper ston

Great point Karl- I was hoping you'd chime in!
When this discussion started in another thread, I wrote this:
"Rounds present the smallest "window" of acceptable depths- therefore allow less examples of stones at the extreme- and the extreme stones will be informative."

So, yes, we need to look at fancy shapes to show the exceptions to the "common sense" part.
What's the depth range on the Octavia's?

Any other "counter-intuitive" examples you can think of?

 

[Karl_K]

Re: Do shallow stones always face up larger than deeper ston

I am hesitant to talk about Octavia directly due to self promotion.

Lets just say that a step cut with a depth of 75% can have the same spread as one with a 65% depth.

Princess cuts are another cut that depth and spread are not always related.
The spread of a princess is dependent on how wide the pavilion is cut.
The wider the pavilion the less spread because more of the weight is in the pavilion.

 

[Karl_K]

Re: Do shallow stones always face up larger than deeper ston

"Rounds present the smallest "window" of acceptable depths- therefore allow less examples of stones at the extreme- and the extreme stones will be informative."

That is because other the the lgf depth all the facet sizes and shape are locked into place if your going to get a decent lab symmetry grade.
Fancies are much more freehand, for example with a step cut you can start your p2,p3,c2,c3 facets in many different places.
The proper placement relies on the skill of the cutter not the facet design.
As matter of fact having to place them in a certain area if you want a consistent outcome is what makes them so hard to cut well compared to a RB.

 

[Circe]

Re: Do shallow stones always face up larger than deeper ston

"Rounds present the smallest "window" of acceptable depths- therefore allow less examples of stones at the extreme- and the extreme stones will be informative."

That is because other the the lgf depth all the facet sizes and shape are locked into place if your going to get a decent lab symmetry grade.
Fancies are much more freehand, for example with a step cut you can start your p2,p3,c2,c3 facets in many different places.
The proper placement relies on the skill of the cutter not the facet design.
As matter of fact having to place them in a certain area if you want a consistent outcome is what makes them so hard to cut well compared to a RB.

So ... we've locked ourselves into a system that punishes creativity and/or further evolution of what constitutes an "ideal" stone? Oy. Explains why every variation on a round needs to be its own branded line, I suppose ....

 

[Rockdiamond]

Re: Do shallow stones always face up larger than deeper ston

That is such a salient point Circe!!!

I think comparisons to art are perfect- as judging both diamonds and art requires a great deal of subjective input.
When new ground is broken, many will find it objectionable- if for no other reason than they've become accustomed to looking at a particular type of design, so a new one is somewhat confrontational.
Hats off to Karl- because he's designed something different, yet it evokes feelings similar, and people have found it easy to accept.

Incorrect usage of the term "ideal" is one of the worst things to happen to the diamond business IMO

 

[Rockdiamond]

Re: Do shallow stones always face up larger than deeper ston

"Rounds present the smallest "window" of acceptable depths- therefore allow less examples of stones at the extreme- and the extreme stones will be informative."

That is because other the the lgf depth all the facet sizes and shape are locked into place if your going to get a decent lab symmetry grade.
Fancies are much more freehand, for example with a step cut you can start your p2,p3,c2,c3 facets in many different places.
The proper placement relies on the skill of the cutter not the facet design.
As matter of fact having to place them in a certain area if you want a consistent outcome is what makes them so hard to cut well compared to a RB.

Karl- I see exactly what you're saying- which dovetails with Circe's point- fancy shape cutting also allows a huge amount of freedom.
Therefore it's best if preconceived notions about depth and facet placement are excluded by cutters- allowing them to make something different.
Also why I feel harshly assessing stones merely based on depth leads to results that may exclude some amazing stones.

 

[Karl_K]

Re: Do shallow stones always face up larger than deeper ston

So ... we've locked ourselves into a system that punishes creativity and/or further evolution of what constitutes an "ideal" stone? Oy. Explains why every variation on a round needs to be its own branded line, I suppose ....

It is more fundamental than that with a RB.
The faceting design locks in the size, shape and location of the facets.
You can vary a few things here and there(star length, table size) but they are still locked together. (see image)
The only one not locked in is lgf% the rest are locked in.

But overall yes cut grading has harmed creativity and the possibility of new cuts gaining wide acceptance.

 

[Karl_K]

Re: Do shallow stones always face up larger than deeper ston

Compare that to an asscher where you have rows of facets hanging out in space.

 

[coati]

Re: Do shallow stones always face up larger than deeper ston

But overall yes cut grading has harmed creativity and the possibility of new cuts gaining wide acceptance.

I agree. And there is so much beauty in a plump crown-like with the Octavia. What certain cuts lack in "spread" they make up for in profile and angled viewing. It's not always about the face-up appearance. I'm an all angles kind of gal.

 

[Rockdiamond]

Re: Do shallow stones always face up larger than deeper ston

Karl's point about the design of a modern round brilliant, and how it restricts innovation is well taken.
But how would you guys say that cut grading for rounds affects cut innovations in fancy shapes?

 

[Karl_K]

Re: Do shallow stones always face up larger than deeper ston

Karl's point about the design of a modern round brilliant, and how it restricts innovation is well taken.
But how would you guys say that cut grading for rounds affects cut innovations in fancy shapes?

There isn't a cut grade for them so we are not interested, has been heard more than once when shopping a custom design around to cutters by more than one designer some of whom are very well connected and well known in the industry (more so than I am).

 

[coati]

Re: Do shallow stones always face up larger than deeper ston

I think it's a follow-the-money scenario. How many are willing to invest in fancy cut innovation?

I see restriction in rb grading-especially as a lover of OECs. Many feel rbs have been said and done with the "tightest" cuts possible, but I think patterning and proportions of rounds can continue to evolve as we've seen with the AVRs and other round cuts. I'd like to see more.