Is this considered deep/steep?

[FB.]

Date: 11/23/2009 10:47:40 AM
Author: rockabee

Date: 11/23/2009 10:01:50 AM
Author: FB.
Shallower pavilions tend have dark arrows against a light background, which can make the stone appear dark in the middle.
Steeper pavilions have light arrows agasint a dark background, which can make the stone apear dark in the middle.

Something in between is ideal - 34.5/40.8, 35.0/40.6, 34.0/41.0 is a good balance. You can push to 35.0/41.0 and still only barely notice the effect of steep/deep. But go to 35.0/41.2 or 35.5/41.0 and it will be obvious.

Slightly steep/deep seem to perform OK. I have one myself.
Severe steep/deep have impaired sparkle from the middle of the stone.

what about steep/shallow? i saw a 37/40.0 stone with 57 table that had fire coming out of the stars/bezel like crazy. but it had an absolutely dead center under the table. was i just seeing things or does the math work out such that those dimensions would have a dark center as well?

See the post that I''ve just made above this one.

 

[FB.]

John

I'm not claiming that the GIA study got it right - but just as the majority of people on here will go for a lower colour and higher cut, the majority of the observers in the GIA's test conditions must have seen something desirable about steep/deep.
What I think would have been better is if GIA had a grade above "excellent" that slotted into the middle of their "excellent" cut grade. That would rival the AGS criteria.

What is noticeable from the nine pictures is that the steep/deeps (odd numbers) have an inversion of the black/white of the arrows. Maybe quite a few people prefer that look - certainly my OH does like that look, whereas I like the opposite, with darker arrows.

 

[John P]

Date: 11/23/2009 11:02:54 AM
Author: FB.

Here''s a pic of a 34.6/40.8 ideal on the left and a 35.0/40.2 on the right. Notice the darker arrows under the table of the second stone. I believe that many here refer to it as ''obstruction'' - a reflection of your silhouette.

Obstruction is a blocking of the light source. Diamond photographs are usually a good example, where the camera lens blocks primary light and you see an even pattern of the pavilion mains.

Obscuration is more tied to reflection. It can also be obstruction (it often is - and is in your example), but obscuration happens regardless of whether it''s blocking the light source(s).

 

[John P]

Date: 11/23/2009 11:10:28 AM
Author: FB.
John

I'm not claiming that the GIA study got it right - but just as the majority of people on here will go for a lower colour and higher cut, the majority of the observers in the GIA's test conditions must have seen something desirable about steep/deep.
What I think would have been better is if GIA had a grade above 'excellent' that slotted into the middle of their 'excellent' cut grade. That would rival the AGS criteria.

I'm with you there. Certainly the old AGS pre-2005 metric underwent revisions. Maybe GIA will adopt the idea.

What is noticeable from the nine pictures is that the steep/deeps (odd numbers) have an inversion of the black/white of the arrows. Maybe quite a few people prefer that look - certainly my OH does like that look, whereas I like the opposite, with darker arrows.

It's groovy that you took the time to look at the arrows. Under what lighting do you and your OH do this?

 

[FB.]

Our lounge and dining room have a dozen low-power bulbs encaused in frosty-glass covers in a kind of variant chandalier (bulbs are very similar to the 10W one's fitted to microscopes).
This gives us diffuse illumination that emphasises the face-up white appearance of the stone. It seems to be in that lighting where we can see the arrows.
At distances up to about 1ft, you can just about see the individual arrows of the stone, radiating out. Beyond that, our eyes can only notice that the stone has a black-white alternating pattern.

Our kitchen and bathrooms have several large, high-power halogen spotlights, which help show the fire, but make all stones look dark.

 

[Rockdiamond]

Date: 11/23/2009 10:48:08 AM
Author: John Pollard

Date: 11/23/2009 9:10:53 AM
Author: FB.
The GIA cut grading system was largely determined by getting a large number of people to view a large number of stones.
However, it can be argued that the stones were not mounted and were in a different lighting environment to the average household or office.
But the fact remains that -for whatever reason- some people preferred steep/deep.

Around 300 people, most in the trade, made 70,000 observations. ''For whatever reason'' may be attributable to the large obstruction metric (larger than AGSL''s avg modeling by about 10 degrees). It explains the GIA metric''s center, which favors steep/deep to shallow.

I suspect that in a steep/deep, the paler arrows (which seem to be reflective and contrasted against the slight darkness on the table) may have been what some observers found pleasing to the eye.
Certainly, my OH prefers stones that have the less-dark arrows - often found in deeper pavilion stones.

A stone of 40.4/35.0 would have quite prominent and contrasting black arrows.
A stone of 40.7/34 would have medium-intensity black arrows.
A stone with 41.0/33 has arrows that are only slightly contrasted.
It is interesting to note that GIA''s excellent grade (determined by real observations) stops at 40.6 pavilion - suggesting a slight dislike of over-contrasted arrows and the steep/deep allows for arrows that are not too prominent.

In real life viewing the appearance of the pavilion mains depends on the lighting conditions as well as the specific diamond. And diamonds are dynamic. Those ''arrows'' seen in magnified static images are tiny and will be flashing on-off, broken up by virtual facet-patterns in real life. Even when held still, lighting and viewer position influence how even the most symmetrical patterns appear. I''d mention also that the average level of cut quality doesn''t produce crisp even ''arrows'' as we frequently see them here. Go into a mall store with a H&A viewer or ideal-scope and you''ll find that such crisp patterning is a rare animal.

With that said, here is a look at a number of actual diamonds, all GIA EX.

1,3,5,7,9 are steeper than my normal recommendations but I''m an admitted cut purist: My goal is cutting for strongest visual appeal through the broadest range of normal lighting conditions. As such the GIA EX grade may be too wide for my personal taste - but I feel it''s positive for consumers and its introduction in 2006 was a major boon for us all.

Now look at the images taken on white and black backgrounds, below. You can see how 2, 6, 8 change in appearance the least when the background is changed. Under-table leakage does crop up in some of the others. Whether such leakage is negative enough to concern you is a personal decision, but it''s a factor that some experts avoid in diamond selection.

Article here.

Excellent photos John!!
I do believe they are extremely illustrative.

A point I make here very often is that terms are thrown around that have a lot of implications.
"Steep Deep" sounds bad- maybe it''s just me, but the term never seemed to be used in a complimentary manner.

"Obstruction issues" is another.
Who would want a stone with "issues"

I love your photos because the show some subtle differences in the diamonds.
You have stated you have certain preferences- as do all of us.

Can anyone state with certainty that the issues they see in these photos would be seen as issues by everyone else looking?
Or is the difference between one GIA EX cut grade, and another more of a preference and taste issue?

I again ask- who to trust?
GIA who inspected the stone, and called it EX cut grade, then personally inspected by the buyer?
Or should we use measurements to deduce what the stone looks like- and then have people tell us whether it''s good or bad using their own preferences as a yard stick?


Happy_79
By all means make sure you inspect the diamond under a variety of lighting environments. Daylight, normal room lighting, dim lighting- as well as bright store spotlights ( I''ll bet you probably would have done that anyway)

Personally I prefer a slightly different set of proportions, however the stone you''re looking at was graded EX cut grade by GIA.
It''s got a reasonable spread for it''s weight.
You are not wrong if you love the diamond.

At this point, using your eyes is the correct thing to do in my book.

 

[John P]

Date: 11/23/2009 11:50:14 AM
Author: FB.

Our lounge and dining room have a dozen low-power bulbs encaused in frosty-glass covers in a kind of variant chandalier (bulbs are very similar to the 10W one's fitted to microscopes).
This gives us diffuse illumination that emphasises the face-up white appearance of the stone. It seems to be in that lighting where we can see the arrows.
At distances up to about 1ft, you can just about see the individual arrows of the stone, radiating out. Beyond that, our eyes can only notice that the stone has a black-white alternating pattern.

What an interesting setup. It sounds like diffuse-utopia. I imagine you enjoy the opportunity to see patterning in a way most people don't. If you ever want a dinner guest...

Our kitchen and bathrooms have several large, high-power halogen spotlights, which help show the fire, but make all stones look dark.

We had a setup like that in the master bath and I found it far too direct, as you report. I changed the spots to a series of eight clear transparent bulbs over the main mirror (60W apiece) and placed mostly-transparent bowl-fixtures underneath them to redirect light up a white angled wall to the ceiling (14'). A second large mirror over the bath reflects the fixtures and up-wall lighting, so it becomes a hemisphere of semi-direct with white reflected from on-high. I can barely coax the wife out of there sometimes.

 

[FB.]

Yes, John - we get to see some very interesting light performance.
The halogens in the bathrooms are too powerful. Laying in the bath with a pair of halogens in your face is not particularly relaxing, although it''s fine if I''m taking a shower. I tend use the shaving light above the mirror for more gentle illumination while in the bath.
I have replacements for the bathroom halogens that I intend to fit in coming weeks. But the kitchen halogens are very useful.