An interesting (to me) ASET comparison -- JA vs. DiamCalc

[drk14]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

Part of the issue is the crispness of a virtual facet needs motion to be seen.
A crisp virtual facet is like a light bulb on a switch on and of on and off.
A less crisp virtual facet is like the same light bulb on a dimmer where the knob is slowly turned.
Both can look the same in a static ASET image both virtual and real.
That is also incredibly complex to account for all the factors that affect it.

Karl,
Would you mind explaining the above?

Obviously, the on/off description is an analogy (and an apt one!), but in actuality, the only way that motion can cause a virtual facet to appear to turn on and off is if some light-dark boundary is reflected in the facet and towards the eyes of the observer; with motion, the reflected image moves so that the observer sees first the dark region, then the boundary, then the light region (or vice versa). Because the relected rays can rotate faster than the angle of rotation of the diamond, it gives the illusion of turning the facets on and off.

Now, to my confusion: To get an non-crisp effect that looks like a "bulb on a dimmer where the knob is slowly turned", assuming my description above is sufficiently accurate for purposes of discussion, the only way this can happen is if one has a blurry boundary between the light and dark zones that traverse the virtual facet (to cause the on-off effect). Most likely the light-dark boundary is due to a pair of neighboring facets somehere else in the diamond. Thus, wouldn't it be true that the root cause of the "dimmer" effect that you described is ultimately a fuzzy boundary between two virtual facets? And if so, wouldn't we also see such fuzzy boundaries in the static image?

 

[drk14]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

If you look at the wire frame output from a diamond scan you will often see facets that don't exist on the real diamond or facets that don't line up the way they do on the real diamond.
*snip*

This is an excellent overview Karl. You should turn it into an article. In your spare time.
Of course you would also want to hit on the strengths as well as weaknesses. It is a pretty incredible technology.

I agree with Bryan: Thank you, Karl!

 

[MelisendeDiamonds]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

If you look at the wire frame output from a diamond scan you will often see facets that don't exist on the real diamond or facets that don't line up the way they do on the real diamond.

In my experience a few extra small facets from scan error which are angled very close(within scanning error 0.0 - 0.1 degrees) to the original facet have negligible impact on the DC generated ASET image for most brilliant cuts such as this Marquise.

ASET angular ranges are wide so unless scanning error creates a change in a ray at a border Red/Green or Blue/Red it will rarely make much of a difference on the appearance.

 

[MelisendeDiamonds]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

Not looking to take this down a rabbit hole. I'm claustrophobic and a little afraid of the dark. And rabbits.

But, what would you say to drk's theory that a CG ASET (from a good scan) could be misleading vs a well captured real ASET photo in terms of crispness of the facet patterns. Is this a weakness of CG ASET?

I don't find anything misleading about a generated ASET from a decent scan in brilliant cuts. They may not be exactly like the photographed ASET for a variety of reasons but the match is usually good enough for me to make an accurate general assessment.

 

[John P]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

They may not be exactly like the photographed ASET for a variety of reasons but the match is usually good enough for me to make an accurate general assessment.

Agreed.

 

[Karl_K]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

They may not be exactly like the photographed ASET for a variety of reasons but the match is usually good enough for me to make an accurate general assessment.

Agreed.

Except when it don't and if you don't have a real image to compare. how do you know?

 

[Karl_K]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

Part of the issue is the crispness of a virtual facet needs motion to be seen.
A crisp virtual facet is like a light bulb on a switch on and of on and off.
A less crisp virtual facet is like the same light bulb on a dimmer where the knob is slowly turned.
Both can look the same in a static ASET image both virtual and real.
That is also incredibly complex to account for all the factors that affect it.

Karl,
Would you mind explaining the above?

Obviously, the on/off description is an analogy (and an apt one!), but in actuality, the only way that motion can cause a virtual facet to appear to turn on and off is if some light-dark boundary is reflected in the facet and towards the eyes of the observer; with motion, the reflected image moves so that the observer sees first the dark region, then the boundary, then the light region (or vice versa). Because the relected rays can rotate faster than the angle of rotation of the diamond, it gives the illusion of turning the facets on and off.

Now, to my confusion: To get an non-crisp effect that looks like a "bulb on a dimmer where the knob is slowly turned", assuming my description above is sufficiently accurate for purposes of discussion, the only way this can happen is if one has a blurry boundary between the light and dark zones that traverse the virtual facet (to cause the on-off effect). Most likely the light-dark boundary is due to a pair of neighboring facets somehere else in the diamond. Thus, wouldn't it be true that the root cause of the "dimmer" effect that you described is ultimately a fuzzy boundary between two virtual facets? And if so, wouldn't we also see such fuzzy boundaries in the static image?

Just so you don't think I am ignoring you, I need to think about how to explain it in an easy manner.
It is complex. More later.

 

[drk14]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

Just so you don't think I am ignoring you, I need to think about how to explain it in an easy manner.
It is complex. More later.

Thanks, Karl. Yes, it took me over 200 words just to formulate the question, so I can appreciate that an explanation won't be easy to compose. Nonetheless, with a physics and engineering background, I'm not afraid of complexity, so I won't mind a technical answer. Thanks for taking the time.

 

[MelisendeDiamonds]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

They may not be exactly like the photographed ASET for a variety of reasons but the match is usually good enough for me to make an accurate general assessment.

Agreed.

Except when it don't and if you don't have a real image to compare. how do you know?

If you look at the wireframe DC and it shows facets that aren't there, you can hover over them to get their angle and that of the adjacent real facets, if this difference is large enough to matter you get it rescanned but in most cases this isn't necessary for a routine examination.

 

[Karl_K]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

They may not be exactly like the photographed ASET for a variety of reasons but the match is usually good enough for me to make an accurate general assessment.

Agreed.

Except when it don't and if you don't have a real image to compare. how do you know?

If you look at the wireframe DC and it shows facets that aren't there, you can hover over them to get their angle and that of the adjacent real facets, if this difference is large enough to matter you get it rescanned but in most cases this isn't necessary for a routine examination.

That only works when you have DC and the data, if you just have the image it doesn't help.

 

[Texas Leaguer]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

I guess if we back up a bit to the original post we can take away a few basic things without getting too far down the rabbit hole:

1) a well taken ASET photo and a computer generated ASET from a good scan are very similar. Having both can reinforce the validity of one another (or indicate a problem with one).
2) Despite possible variables introduced by the photo setup, operator skill, and instrumentation error of the scanner, the images provide useful information related to the performance and potential beauty of the diamond.
3) An ASET image, (either CG or actual) will not be able to tell you everything you need to know about a given diamond.

This is a case study where the diamond's predicted performance based upon its ASET signature was born out by real life observation. It follows that if a consumer was shopping for a nice performing marquise and saw a candidate with an ASET signature similar to this one, it would be worth further consideration and taking a look at in real life.

As with any tool, understanding the strengths and limitations of it, and employing it for the right purposes, determines its value.

 

[Karl_K]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

here is part of the answer:
This is my favorite DC lighting with the DC default tolk diamond.


Here is the lighting map:

 

[Karl_K]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

Now you would think you would get little scintillation if it was caused by light boundaries.
You would be right but there is more to the story....
Lets look at where the diamond is drawing light from by putting it in sphere with that lighting...

 

[Karl_K]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

Lets look at the side view of the sphere....
Note: this is just a small part of what goes on overall......

 

[MelisendeDiamonds]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

I guess if we back up a bit to the original post we can take away a few basic things without getting too far down the rabbit hole:

1) a well taken ASET photo and a computer generated ASET from a good scan are very similar. Having both can reinforce the validity of one another (or indicate a problem with one).
2) Despite possible variables introduced by the photo setup, operator skill, and instrumentation error of the scanner, the images provide useful information related to the performance and potential beauty of the diamond.
3) An ASET image, (either CG or actual) will not be able to tell you everything you need to know about a given diamond.

This is a case study where the diamond's predicted performance based upon its ASET signature was born out by real life observation. It follows that if a consumer was shopping for a nice performing marquise and saw a candidate with an ASET signature similar to this one, it would be worth further consideration and taking a look at in real life.

Agreed.

 

[Karl_K]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

I guess if we back up a bit to the original post we can take away a few basic things without getting too far down the rabbit hole:

1) a well taken ASET photo and a computer generated ASET from a good scan are very similar. Having both can reinforce the validity of one another (or indicate a problem with one).
2) Despite possible variables introduced by the photo setup, operator skill, and instrumentation error of the scanner, the images provide useful information related to the performance and potential beauty of the diamond.
3) An ASET image, (either CG or actual) will not be able to tell you everything you need to know about a given diamond.

This is a case study where the diamond's predicted performance based upon its ASET signature was born out by real life observation. It follows that if a consumer was shopping for a nice performing marquise and saw a candidate with an ASET signature similar to this one, it would be worth further consideration and taking a look at in real life.

As with any tool, understanding the strengths and limitations of it, and employing it for the right purposes, determines its value.

well said.

 

[John P]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

They may not be exactly like the photographed ASET for a variety of reasons but the match is usually good enough for me to make an accurate general assessment.

Agreed.

Except when it don't and if you don't have a real image to compare. how do you know?

Key to this: Decent scan. Brilliant cut. General assessment.

No different than using an ideal-scope or ASET loupe and tweezers to pick high performing melee from a parcel. General assessment. Not trying to dissect things nearly as much as the conversation here purports-to, which I also like doing, and requires more surgical analysis.

 

[Rockdiamond]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

I guess if we back up a bit to the original post we can take away a few basic things without getting too far down the rabbit hole:

1) a well taken ASET photo and a computer generated ASET from a good scan are very similar. Having both can reinforce the validity of one another (or indicate a problem with one).
2) Despite possible variables introduced by the photo setup, operator skill, and instrumentation error of the scanner, the images provide useful information related to the performance and potential beauty of the diamond.
3) An ASET image, (either CG or actual) will not be able to tell you everything you need to know about a given diamond.

This is a case study where the diamond's predicted performance based upon its ASET signature was born out by real life observation. It follows that if a consumer was shopping for a nice performing marquise and saw a candidate with an ASET signature similar to this one, it would be worth further consideration and taking a look at in real life.

As with any tool, understanding the strengths and limitations of it, and employing it for the right purposes, determines its value.

+1
Agree 100%

 

[Karl_K]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

top same image from above...
Below 2 degree tilt which is just a very slight movement of the hand.
Notice how much the placement and distribution of the light draw has changed.
This is where scintillation starts but it can not be totally explained in this simple a manner there are far more variables.

 

[Texas Leaguer]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

top same image from above...
Below 2 degree tilt which is just a very slight movement of the hand.
Notice how much the placement and distribution of the light draw has changed.
This is where scintillation starts but it can not be totally explained in this simple a manner there are far more variables.

To my eye while the placements have shifted, the overall distribution remained pretty stable.

 

[Karl_K]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

top same image from above...
Below 2 degree tilt which is just a very slight movement of the hand.
Notice how much the placement and distribution of the light draw has changed.
This is where scintillation starts but it can not be totally explained in this simple a manner there are far more variables.

To my eye while the placements have shifted, the overall distribution remained pretty stable.

2 degrees right is a very tiny movement.
Lets try 5 down and 5 right which is still a small movement. It is much more obvious now.

 

[Texas Leaguer]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

top same image from above...
Below 2 degree tilt which is just a very slight movement of the hand.
Notice how much the placement and distribution of the light draw has changed.
This is where scintillation starts but it can not be totally explained in this simple a manner there are far more variables.

To my eye while the placements have shifted, the overall distribution remained pretty stable.

2 degrees right is a very tiny movement.
Lets try 5 down and 5 right which is still a small movement. It is much more obvious now.

That certainly shuffles the deck. The symmetrical patterns have now given way to a more chaotic spread. But it is interesting that the overall coverage is still quite full. If anything a little more full. Is that from multiplication of virtual facets?

 

[Karl_K]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

That certainly shuffles the deck. The symmetrical patterns have now given way to a more chaotic spread. But it is interesting that the overall coverage is still quite full. If anything a little more full. Is that from multiplication of virtual facets?

It could be, I am not sure.
It does sound plausible.

 

[drk14]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

Lets try 5 down and 5 right which is still a small movement. It is much more obvious now.

I'm not sure what part of this is supposed to be obvious.

Other than the fact that all the dots have moved, the main thing I noticed is that there are more dots near the equator of the sphere in the tilted view.

I have no experience with the DC software, so I don't know how to read the light map, or the spherical projections of the rays.

I believe the latter is a reverse trace of light rays from an observer's eye that is looking at a diamond, following the reversed ray until it exits the diamond and intersects a sphere centered around the diamond; thus showing the various angular directions from which light enters the diamond to produce an image in the observer's eye. So kind of like a 3-dimensional ASET.

But I still don't know what I'm supposed to learn by comparing the spheres of the tilted and non-tilted diamonds. Or how this explain why in some cases, virtual facets turn on/off abruptly, and in other cases transition gradually.

 

[Karl_K]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

Lets try 5 down and 5 right which is still a small movement. It is much more obvious now.

I'm not sure what part of this is supposed to be obvious.
That small amounts of tilt produce fairly large differences where the diamond is getting light from.
Other than the fact that all the dots have moved, the main thing I noticed is that there are more dots near the equator of the sphere in the tilted view.

I have no experience with the DC software, so I don't know how to read the light map, or the spherical projections of the rays.

I believe the latter is a reverse trace of light rays from an observer's eye that is looking at a diamond, following the reversed ray until it exits the diamond and intersects a sphere centered around the diamond; thus showing the various angular directions from which light enters the diamond to produce an image in the observer's eye. So kind of like a 3-dimensional ASET.
Yes

But I still don't know what I'm supposed to learn by comparing the spheres of the tilted and non-tilted diamonds. Or how this explain why in some cases, virtual facets turn on/off abruptly, and in other cases transition gradually.

I was addressing the comment about light boundaries and scintillation and how there is more to it than that.
I haven't got to the rest yet.

 

[drk14]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

I was addressing the comment about light boundaries and scintillation and how there is more to it than that.
I haven't got to the rest yet.

OK, thanks, I wasn't sure if there were additional installments coming in your explanation, or if I was just lost!

 

[Karl_K]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

I was addressing the comment about light boundaries and scintillation and how there is more to it than that.
I haven't got to the rest yet.

OK, thanks, I wasn't sure if there were additional installments coming in your explanation, or if I was just lost!

Ok, here are some things to consider before we go on:
a: virtual facets are created by the interaction of the real facets.
b: virtual facets are relative to the viewer, three people standing side by side looking at a diamond will each see virtual facets that don't exist to the other viewers in that apparent location size, shape and where they draw and return light.
c: virtual facets change shape, location, size, number and where they draw and return light with movement of the viewer and or the diamond.(changes in viewing angle changes them)

I like to think of it that virtual facets are created and destroyed as the viewing angles change but other experts do not like that wording but it is what makes it click in my mind.

 

[drk14]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

Ok, here are some things to consider before we go on:

Following you so far.

Is it safe to say that each spot on the sphere maps to one virtual facet?

 

[Karl_K]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

Ok, here are some things to consider before we go on:

Following you so far.

Is it safe to say that each spot on the sphere maps to one virtual facet?

No, one VF may draw light from multiple locations and 2 VFs can draw light from the same general location.
Particularly with large virtual facets.
Which brings us to part one.
With large virtual facets with there show change rate are more sensitive to yawed and or wavy facets.
The will often split into 2 or more virtual facets if formed by yawed facets under tilt.
It also can effect the snappy on and off appearance of scintillation from them.

yawed = twisted facets that are not aligned in 3d. Because the wheel rotates in one direction it wants to cut more on one end of the facet and for precision cutting this must be accounted for.
[URL='https://www.pricescope.com/community/threads/facet-yaw.21857/']https://www.pricescope.com/community/threads/facet-yaw.21857/[/URL]
[URL='https://www.pricescope.com/community/threads/azimuth-shift-yaw.33257/']https://www.pricescope.com/community/threads/azimuth-shift-yaw.33257/[/URL]

wavy facets are often the result of hardness variations in the diamond and can load to lower polish scores.
They can also be caused by vibration in the cutting process. Eliminating vibration has been one area where great strides have been taken in improving diamond cutting technology.

 

[drk14]

Re: An interesting (to me) ASET comparison -- JA vs. DiamCal

Is it safe to say that each spot on the sphere maps to one virtual facet?

No, one VF may draw light from multiple locations

But multiple locations on the sphere suggests that the reverse ray-trace (from the eye through the diamond to the sphere) was bifurcated at some point -- doesn't this imply that the ray has hit a facet boundary (how else would the ray split?), and wouldn't this therefore create two distinct virtual facets for the viewer?

2 VFs can draw light from the same general location.

OK, but is this just a limitation of the software (or the rendering of the sphere)? That is to say, under this scenario, if we were able to zoom in on such a spot on the surface of the sphere (i.e., "the same general location" that serves as a light source for two distinct VFs), would we then see two distinct spots if the spatial resolution was sufficient?


And with regards to wavy facets: Are these accounted for in computer-generated ASETs?