What is transitional cut?

[strmrdr]

Here is an RB and a transitional model with the exact same crown and pavilion angles and table size.

 

[strmrdr]

This image shows the fire difference in a thousands of points of light view. (Similar but not the same as Marty lighting)
Notice the Transitional has fewer but larger fire patches.

 

[Eva17]

karl,

thank you for the two new photos comparisons. they are great.

you are always so helpful!!!!

 

[stone-cold11]

Karl,

Is there a definite preference of the consumers for modern RB? I am wondering because from what I understand, there seems to be a trend towards larger LGF, from transitional to modern RB, but from the point of weight retention and cutters, shouldn''t a lower LGF meant greater weight from the rough?

Cutters should not have a preference for larger LGF unless driven by consumers market, if I am reading that correctly.

 

[Allison D.]

Date: 1/26/2009 12:09:37 AM
Author: strmrdr
This image shows the fire difference in a thousands of points of light view. (Similar but not the same as Marty lighting)
Notice the Transitional has fewer but larger fire patches.

Karl, does the software allow you to make changes to the graphic?

Most of the transitional stones I've seen have a smaller culet, which seems to increase the 'chunky' look.

 

[strmrdr]

Date: 1/26/2009 9:09:38 AM
Author: Stone-cold11
Karl,


Is there a definite preference of the consumers for modern RB? I am wondering because from what I understand, there seems to be a trend towards larger LGF, from transitional to modern RB, but from the point of weight retention and cutters, shouldn''t a lower LGF meant greater weight from the rough?


Cutters should not have a preference for larger LGF unless driven by consumers market, if I am reading that correctly.

Changes in indoor lighting from low soft lighting to brighter harsher lighting drove the change to the modern RB.
It also made the princess cut possible.

 

[strmrdr]

Date: 1/26/2009 10:16:39 AM
Author: Allison D.

Date: 1/26/2009 12:09:37 AM

Author: strmrdr

This image shows the fire difference in a thousands of points of light view. (Similar but not the same as Marty lighting)

Notice the Transitional has fewer but larger fire patches.

Karl, does the software allow you to make changes to the graphic?


Most of the transitional stones I''ve seen have a smaller culet, which seems to increase the ''chunky'' look.

Yes I can change it anyway needed, I kept the culet pointed as to point out the changes in lgf% made without adding another variable.
There were transitional cuts with no culet cut but they are rather rare(I have seen photos of one) as it was thought to help prevent breakage to polish them down.

 

[Eva17]

Date: 1/26/2009 10:33:21 AM
Author: strmrdr

Date: 1/26/2009 9:09:38 AM

Author: Stone-cold11

Karl,


It also made the princess cut possible.

could you please explain why?

 

[strmrdr]

Date: 1/26/2009 10:37:53 AM
Author: Eva17

Date: 1/26/2009 10:33:21 AM

Author: strmrdr

Date: 1/26/2009 9:09:38 AM


Author: Stone-cold11


Karl,



It also made the princess cut possible.

could you please explain why?

tiny virtual facets don''t work well in candle and lamp light because of the small light gathering area.

This will tell you what virtual facets are:

http://journal.pricescope.com/Articles/61/1/Virtual-Facets-and-patterns%2c-a-Discussion-about-step-cuts-.aspx

 

[Rhea]

Great photos and explaination. I''ve never been able to see much of a difference between RBs and Transitions, still not sure if I could but this does help.

 

[strmrdr]

woops see below...

 

[strmrdr]

With a princess cuts the virtual facets I pointed to are the largest virtual facets they are fairly small and few in number.
These are the facets other than glare that are most likely to return light in dim soft lighting.
Brighter and more direct light allows the smaller virtual facets to work.

 

[strmrdr]

With a RB there are to many larger virtual facets to draw arrows to but you can see it has many larger virtual facets than the princess cut and the largest are much larger.

 

[strmrdr]

Here are the virtual facets for a transitional with the same angles as the rb above.
It has fewer total virtual facets than the princess or the RB but they are much larger.

 

[strmrdr]

Here are the oec virtual facets they are similar to the transitional cut with variations in locations and size but overall they would have similar performance in dim soft lighting.
This one I added a large culet which is the circle in the center and you can see its 8 reflections also(arrows point to the reflections).
This is a good demonstration how the facets interact to create virtual facets.
1 culet interacts to create 8 virtual facets.

 

[strmrdr]

forgot the image...

 

[Eva17]

i love the images of the transitional and the oec.


especially when you see the virtual cutlet reflections.

 

[strmrdr]

This image brings it all together and shows the effects of the virtual facets and how the light is split up in different ways.

 

[stone-cold11]

Karl, thanks for the wonderful explanation and demonstration.

 

[coatimundi_org]

Date: 1/26/2009 5:28:05 PM
Author: strmrdr
This image brings it all together and shows the effects of the virtual facets and how the light is split up in different ways.

How cool Storm--thank you for the visual explanation! The transitional facet pattern is my favorite, and I must say live and in person, my new trans blow my ideal cut out of the water.

Storm, I have a question:

I did a visual estimation of the crown and pavilion angles on these transitionals. (pictured below) I overestimated at first--on the crowns(thought they were shallower, but on closer examination, they appear to range from 32 to 34.5ish The pavilion angles are around 40.8 and the tables are each around or above 60%. (larger than I normally prefer.)

These stones display more fire and brilliance than my ACA--34.6ca, 40.7pa, 57.1-table.

I''m curious about the fire, because of the larger tables and slightly shallower crowns. I took into consideration that I might be distracted by larger flashes of fire, but I don''t think that''s the case. Any thoughts?

 

[Upgradable]

Date: 1/26/2009 6:29:04 PM
Author: coatimundi

Date: 1/26/2009 5:28:05 PM
Author: strmrdr
This image brings it all together and shows the effects of the virtual facets and how the light is split up in different ways.

How cool Storm--thank you for the visual explanation! The transitional facet pattern is my favorite, and I must say live and in person, my new trans blow my ideal cut out of the water.

Storm, I have a question:

I did a visual estimation of the crown and pavilion angles on these transitionals. (pictured below) I overestimated at first--on the crowns(thought they were shallower, but on closer examination, they appear to range from 32 to 34.5ish The pavilion angles are around 40.8 and the tables are each around or above 60%. (larger than I normally prefer.)

These stones display more fire and brilliance than my ACA--34.6ca, 40.7pa, 57.1-table.

I''m curious about the fire, because of the larger tables and slightly shallower crowns. I took into consideration that I might be distracted by larger flashes of fire, but I don''t think that''s the case. Any thoughts?

Coati- this doesn''t answer your question at all, but I just wanted to point out how the actual picture of your center stone reflect precisely the diagrams Karl posted!!

 

[glitterata]

What a great thread!

I thought I''d add a couple of pictures of my late-1920s transitional cut.

 

[Eva17]

Date: 1/26/2009 6:42:27 PM
Author: glitterata
What a great thread!


I thought I''d add a couple of pictures of my late-1920s transitional cut.

look at that beautiful pattern and those colors in your bottom pix!!

 

[Porridge]

Oooh Karl that is so helpful!
You rock!

 

[strmrdr]

Date: 1/26/2009 6:29:04 PM
Author: coatimundi

Date: 1/26/2009 5:28:05 PM

Author: strmrdr

This image brings it all together and shows the effects of the virtual facets and how the light is split up in different ways.

How cool Storm--thank you for the visual explanation! The transitional facet pattern is my favorite, and I must say live and in person, my new trans blow my ideal cut out of the water.


Storm, I have a question:


I did a visual estimation of the crown and pavilion angles on these transitionals. (pictured below) I overestimated at first--on the crowns(thought they were shallower, but on closer examination, they appear to range from 32 to 34.5ish The pavilion angles are around 40.8 and the tables are each around or above 60%. (larger than I normally prefer.)


These stones display more fire and brilliance than my ACA--34.6ca, 40.7pa, 57.1-table.


I''m curious about the fire, because of the larger tables and slightly shallower crowns. I took into consideration that I might be distracted by larger flashes of fire, but I don''t think that''s the case. Any thoughts?

It all depends on the lighting.
The amount of fire is more dependent on the lgf% than the crown height with RB style diamonds.
With fancies the crown height is much more important.
The amount of obstruction can change the relative appearance of brilliance.
That is to huge a topic for this thread and this time of night.
Without seeing them side by side at different distances it is hard to say what you are seeing.
I would bet though that you would find lighting and distance where they swap places as to brilliance and fire.

 

[strmrdr]

Date: 1/27/2009 1:13:00 AM
Author: strmrdr
The amount of fire is more dependent on the lgf% than the crown height with RB style diamonds.

That should say style and apparent amount.
A higher crown can shift a RB towards the fire side but doesn''t change the overall appearance as much as changes to the lgf%
As you can see below moving from a TIC to a FIC there are relatively small changes to the virtual facets compared to going from the tic to a transitional shown earlier.

 

[strmrdr]

This combo with a 65% lgf%

 

[K9]

FABULOUS! Thank you so much for continuing to post on this!!! The images are very helpful!

 

[strmrdr]

Is not that far behind a ideal cut RB in light return and in some lighting will beat it.
But the RB will likely be better balanced across multiple lighting conditions.
That is not to say you wouldn''t prefer the trans even when it technically isn''t performing at as high a level as the RB.

 

[coatimundi_org]

Date: 1/27/2009 11:40:23 AM
Author: strmrdr

Date: 1/27/2009 1:13:00 AM

Author: strmrdr

The amount of fire is more dependent on the lgf% than the crown height with RB style diamonds.

That should say style and apparent amount.

A higher crown can shift a RB towards the fire side but doesn''t change the overall appearance as much as changes to the lgf%

As you can see below moving from a TIC to a FIC there are relatively small changes to the virtual facets compared to going from the tic to a transitional shown earlier.

The FIC in your rendering has a slightly smaller pa and slightly shorter lgfs. This type of analysis is making more sense to me vs. the smaller table higher crown idea. I studied 200 rbs in class for fire and brilliance--not as many as you, of course --but enough to see that smaller table-higher crown did not always produce more fire by default.

Now, as I pay more attention to lgfs, I''m seeing new things.

I''m going to snap some comparison shots in various lighting conditions--will post later. The ACA has 78% lgfs, and I have a much larger rb that has 80% lgfs with a 40.8pa and 34.1ca with a 57%table--that is very firey.

Thanks for your response Storm!