Virtual Facets and patterns, a Discussion about step cuts.

There is a new article on Pricescope journal by Karl K ( strmrdr ).


Virtual Facets and patterns, a Discussion about step cuts.


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

I want to thank him for his contribution to the Pricescope community.

Andrey
PS Admin

Thank you Andrey!

Karl, great article on the virtual facets, very clear and concise! Great picture of you too!! I am looking forward to more articles written by you

Date: 8/31/2008 10:17:24 PM
Author: Skippy123
Karl, great article on the virtual facets, very clear and concise! Great picture of you too!! I am looking forward to more articles written by you

Click to expand...

Thanks skippy!!!!

Another great article Karl. Kudos to you, you made it clear and easy to follow. That''s a job in and of itself. Job well done!! I look forward to reading more of them!!! Thanks!!!

Date: 9/1/2008 12:39:50 AM
Author: Kaleigh
Another great article Karl. Kudos to you, you made it clear and easy to follow. That''s a job in and of itself. Job well done!! I look forward to reading more of them!!! Thanks!!!

Click to expand...

Thank you for the kind words!

I have a number of questions:

1. When showing the differences between a virtual facet returning light, leaking light or being obstructed, facet B points to a white area in the idealscope-view (leakage), while the same area is dark green in the ASET-view. Is this a Diamcalc-error, since light-leakage should be black or white in ASET, depending on whether or not one uses backlighting?

2. You are saying that virtual facets of a step cut become bigger as the stone is tilted. Is that calculated? Is that so for the whole stone or only for the central table-area of the stone? Does this remain so when the stone is not cut perfectly symmetrical?

3. You are saying that the size of the virtual facet relates to the size of the flash. That, I think, is logical. Then, you say that a larger flash requires more movement in order to obtain a flash. Is that so? Is that for all diamonds or only for step-cuts? When moving, also the size of virtual facets changes, no? How do you define the term ''flash'' in this regard?

4. In the section ''How does the virtual facet size relate to lighting?'', the videos did not work. You say that in a low light-environment, stones with larger virtual facets will show more flash because they are gathering their light from a bigger area. Isn''t this difference minimal, since one virtual facet clearly gathers all its light from one specific direction? Apart from the term ''flash'', you also use the term ''scintillation event'' in this section, are these synonyms or is there another definition for ''scintillation event''?

Looking forward to your clarifications.

Live long,

Paul,

1: The DC black is showing very very slight light return in that area, ASET white shows it as white as does the IS. DC bug most likely.
On my monitor it is close enough to black that I let it go.
If it is clearly showing up as green for people I need to redo it.

2: Watch the wire move video please.
The virtual facets closest to the viewer get smaller the rest larger.
Overall better than 80% of the virtual facets get larger.
Yes it is the same for non-symmetrical stones that I have scans for and tried it out on.


3: The larger the flash the more movement it takes to move it over the eye and get to the off point. For example: . vs _ it takes more movement to get from the start to the finish of the _
Also the space between flashes is larger with larger virtual facets(more separation) so it takes more movement to get to the next flash.
It applies to all diamonds but a RB once tilted will respond more to smaller movements where the step cut will respond less.
Flash is defined as a beam of light hitting the eye it can be white light or colored light.

4: A ''scintillation event'' can be a flash but a flash isn''t always a ''scintillation event'' as a diamond can have a flash sitting still or in a still picture.
I''m going to change it to flash as I don''t want to have to get into the AGS ''scintillation event'' size description.

Large virtual facets gather light over a larger area even if it is from the same direction and the flash is larger and more likely to be seen. (the proofs are well beyond the scope of the article but the video shows it)

The videos are being problematic despite using a MS codec. I had them tested on a bunch of computers and they worked but it seems there are a large group they don''t work for. I''m going to redo them in another codec. Are all the other videos working for you?

I hope this answers your questions and if you have any more I am happy to clarify.
Thank you for the feedback!!

Here is an experiment anyone can do to demo flash size vs movement.

Take a black piece of paper and use a hole punch to make a line of large holes then take a pen and punch a line of smaller holes.
Then hold it between you and a strong light so the light shines through the holes and move it side to side.

Here is the ASET white.
Do you think I should switch to the ASET white?

Date: 9/1/2008 4:47:46 PM
Author: strmrdr
Here is the ASET white.
Do you think I should switch to the ASET white?

Click to expand...

That is up to you. I just found the current pic confusing, since what is leakage in the IS was green in the ASET.

Date: 9/1/2008 4:25:28 PM
Author: strmrdr
Here is an experiment anyone can do to demo flash size vs movement.

Take a black piece of paper and use a hole punch to make a line of large holes then take a pen and punch a line of smaller holes.
Then hold it between you and a strong light so the light shines through the holes and move it side to side.

Click to expand...

Is this experiment valid? I do not think so.

In the case of a gemstone, a flash (which you define as a beam of light hitting the eye) is obtained by the co-operation of a number of facets. A virtual facet is in the same situation, it is formed by the co-operation of a number of facets.

Whether a virtual facet produces a flash (that is when the beam of light hits the eye) depends on the angles of these facets. Any movement (small or large) causes a change in these angles, and thus in the possibility of producing a flash. What you appear to see in the video (which is just one example, and thus not proof), has another cause than merely the size of the virtual facet.

If you were right and a larger size virtual facet needed more movement to produce a flash, then bigger stones needed to be moved more than smaller stones, as all virtual facets of the big stone with an identical proportion-set-up are bigger than those of the smaller stone.

Your definition of ''flash'' still confuses me, though. You say that it is a beam of light hitting the eye. This does not refer to the beam of light changing from on to off, or vice-versa, does it? Still, I think that your explanation about flash size and movement tries to refer to on/off-effects.

Live long,

Date: 9/2/2008 3:42:25 AM
Author: Paul-Antwerp

Date: 9/1/2008 4:47:46 PM

Author: strmrdr

Here is the ASET white.

Do you think I should switch to the ASET white?

Click to expand...

That is up to you. I just found the current pic confusing, since what is leakage in the IS was green in the ASET.

Click to expand...

Thanks Paul if its confusing it needs to be changed.

Date: 9/1/2008 4:06:16 PM
Author: strmrdr
Paul,

2: Watch the wire move video please.
The virtual facets closest to the viewer get smaller the rest larger.
Overall better than 80% of the virtual facets get larger.
Yes it is the same for non-symmetrical stones that I have scans for and tried it out on.

I hope this answers your questions and if you have any more I am happy to clarify.
Thank you for the feedback!!

Click to expand...

You are welcome, Karl. It is a challenge to consider every aspect of what you are reporting. At first sight, I found both your articles interesting, but reading more in-depth, they constantly raise new question-marks.

I do not get the above explanation. Can you explain it without refering to the video. The video is only one example. For instance, I do not understand if you say ''overall better than 80% of the virtual facets get larger''. I think that you mean that more than 80% of the virtual facets become larger when tilting the stone. This would imply that the gain in size of 80% of the virtual facets is compensated by the other 20% becoming smaller. This sounds tricky to me.

Thinking further, doesn''t the apparent surface of a stone become smaller when tilted? If so, your statement infers that while the total size is becoming smaller, 80% of the virtual facets are becoming bigger. That would mean that the 20% shrink even more than we thought. And these 80% are already the big ones?

Sorry, this seems incorrect to me.

Live long,

Date: 9/1/2008 4:06:16 PM
Author: strmrdr
Paul,

4: A ''scintillation event'' can be a flash but a flash isn''t always a ''scintillation event'' as a diamond can have a flash sitting still or in a still picture.
I''m going to change it to flash as I don''t want to have to get into the AGS ''scintillation event'' size description.

Click to expand...

I too am struggling with these definitions. Can you explain ''flash'' and ''scintillation event'' again? What I read here, just confused me even more.

Live long,

Date: 9/2/2008 3:57:24 AM
Author: Paul-Antwerp

If you were right and a larger size virtual facet needed more movement to produce a flash, then bigger stones needed to be moved more than smaller stones, as all virtual facets of the big stone with an identical proportion-set-up are bigger than those of the smaller stone.

Click to expand...

That is exactly right Paul a .25ct will not have to be moved as much as a 10ct to produce the same number of on/off flashes.
The size and separation of the flashes from the 10ct will be much bigger.

AGS uses absolute size for "scintillation events" the .25ct depending on where they split the sizes out would have all small events.
The 10ct all large events.
As the size of the events increase the separation also increases in identical proportion sets.
Therefore more movement is required.


A flash is a beam of light is right but when the diamond/viewer/light is moved that flash moves over the eye while it exists if it is to be seen.

Date: 9/2/2008 4:13:40 AM
Author: Paul-Antwerp

Date: 9/1/2008 4:06:16 PM

Author: strmrdr

Paul,


4: A 'scintillation event' can be a flash but a flash isn't always a 'scintillation event' as a diamond can have a flash sitting still or in a still picture.

I'm going to change it to flash as I don't want to have to get into the AGS 'scintillation event' size description.

Click to expand...

I too am struggling with these definitions. Can you explain 'flash' and 'scintillation event' again? What I read here, just confused me even more.


Live long,

Click to expand...

When the diamond is moving they can be the same thing depending on how AGS chooses to define it.
Which is why I avoided it as their work isn't done yet and I can't know for sure what their final definition will be.

Here I drew red lines connecting virtual facets that got bigger and green lines connecting some that got smaller.
This is the same image as is in the article.

Here is another proof for movement.
This is a .25ct next to 10ct tolk round in my bathroom hdr lighting.
The relative size to each other is correct.
Lets keep things simple and move the observer rather than the diamond.
The smaller diamond has smaller flashes and smaller separation so for any given movement by the observer would have more apparent flashes.

This matches the paper experiment above.

Date: 9/2/2008 4:22:25 AM
Author: strmrdr

Date: 9/2/2008 3:57:24 AM
Author: Paul-Antwerp

If you were right and a larger size virtual facet needed more movement to produce a flash, then bigger stones needed to be moved more than smaller stones, as all virtual facets of the big stone with an identical proportion-set-up are bigger than those of the smaller stone.

Click to expand...

That is exactly right Paul a .25ct will not have to be moved as much as a 10ct to produce the same number of on/off flashes.
The size and separation of the flashes from the 10ct will be much bigger.

Click to expand...

Now you are refering to on/off flashes again, which is not the same as your earlier definition.

In any case, I disagree completely with you on this.

Paul thank you for challenging me on this as it is forcing me to think of new ways to show it and to re-verify the information I have in my articles.
Because of this discussion there are going to be large changes in my next article in how I present it.
I also want to hunt it down if there is any inaccurate information present.

Paul does this video work for you?
Notice how many more flashes there are with the smaller virtual facets under the crown steps than in the center where the large virtual facets are located.

https://www.pricescope.com/idealbb/files/karl_vid2.avi

I will take another shot at a definition of flash:
A flash is a light beam hitting the eye.
An on/off flash is a flash that appears and disappears.

This is a 4P 3C step asscher with a model based on a sarin scan of an actual diamond.
The scanner just did a so-so job and there are symmetry differences not in the original which makes it a good test of non-symmetrical facets in the outcome.
As you can see the majority of the virtual facets are clearly larger when tilted.
You can even tell which way it is tilted because of the smaller virtual facets at the top.

Here is my proof for RB virtual facets getting smaller when tilted.

Date: 9/2/2008 4:22:25 AM
Author: strmrdr

Date: 9/2/2008 3:57:24 AM
Author: Paul-Antwerp

If you were right and a larger size virtual facet needed more movement to produce a flash, then bigger stones needed to be moved more than smaller stones, as all virtual facets of the big stone with an identical proportion-set-up are bigger than those of the smaller stone.

Click to expand...

That is exactly right Paul a .25ct will not have to be moved as much as a 10ct to produce the same number of on/off flashes.
The size and separation of the flashes from the 10ct will be much bigger.

AGS uses absolute size for ''scintillation events'' the .25ct depending on where they split the sizes out would have all small events.
The 10ct all large events.
As the size of the events increase the separation also increases in identical proportion sets.
Therefore more movement is required.


A flash is a beam of light is right but when the diamond/viewer/light is moved that flash moves over the eye while it exists if it is to be seen.

Click to expand...

Karl I have pointed out to you before to the need to be able to discern the size of a flash (or whatever) for human beings.
This is a weakness in your approach. Without specific methods to know the size of virtual window that can be seen, you can not know anything about virtual facets.

All your modelling is done with a double reflection in DiamCalc. That is based on a DC setting of ''double'', there is no option for triple, quadruple etc. You can model many times more reflections in diamcalc, and the larger the stone, the more of them are able to be discerned.

If you play inside DiamCalc you will find that even up to 10 patern calculations you will see many more extra facets.


In this case AGS are correct, and you should do additional homework.

Paul the DiamCalc Ideal-scope and ASET settings are correct. You may have noticed one of my sayings - brilliance is the enemey of fire. Perhaps you can understand its relevence in this case?

Date: 9/2/2008 3:42:25 AM
Author: Paul-Antwerp

Date: 9/1/2008 4:47:46 PM
Author: strmrdr
Here is the ASET white.
Do you think I should switch to the ASET white?

Click to expand...

That is up to you. I just found the current pic confusing, since what is leakage in the IS was green in the ASET.

Click to expand...

Paul,Karl
it is very typical. One virtual facet could collect light from different directions.
Karl,
You can easy check it by raytracing mode, before agree with wrong Paul statement
at least you can easy see what green is Dark.

Karl,

re:When comparing diamonds of the same size, larger virtual facets - because they have more light gathering area - will produce more flash in soft and low light than diamonds with smaller virtual facets.

Why?

for example in Hemisphere light cut with big facets has not any advantages or disadvantages

Cut with big number virtual facets could have advantages in light with spot light sources . via versa is not correct.

Re: The larger the virtual facets the larger the flashes coming from the diamond will be, but it also takes more movement to make them flash on and off.

Karl,

It is Misleading statement.
Do you mean diamond with big virtual facets or one big virtual facet needs bigger movement to catch light source?

Bigger virtual facet could catch light source faster than small virtual facets ( one big facet will catch one source light more often than one small virtual facet. But diamond with big virtual facets could catch light source much more rare than Princess cut)
Two virtual facets with same size could collect light source with quite different probability. It depends from angular speed.
Virtual facets what create head obscuration have usually low angular speed( could be even zero)
Angular speed( DETAS) and Size are both important to catch light

BTW.
One virtual facets could has strong leakage and have bright green color in ASET in same time

Leakage definition is : Light goes through pavilion facets.

but light from pavilion facet could back to upper Hemisphere( Green or red or even blue