Why doesn't AGS grade cut?

[zoebartlett]

Forgive me if this has been mentioned many times (I'm sure it has!), but I'm wondering why AGS doesn't provide a cut grade on their stones. I was just looking at my center stone's DQR on AGS' site and there wasn't a cut grade listed. All of a sudden, I feel like a newbie because I haven't hung out in RT in a long time. I'm a little embarrassed to admit that! I have all the other specs of the stone but for some reason, it's the one that's missing that I really want to see.

I feel like I should know this...

 

[slg47]

AGS does grade cut. Does yours not say

Cut Grade: ___
Light Performance: ___
Polish: ___
Symmetry: ___

ETA that might be the DQD format. do you have the carat weight and report number?

 

[stone-cold11]

Old DQR format do not have cut grade.

 

[slg47]

Old DQR format do not have cut grade.

oh, interesting! good to know. does it have light performance grade?

 

[stone-cold11]

Nope, old DQR totally does not have cut grade. Present DQR, I think since 2009, only has proportion based cut grade. Only the DQD has the performance based cut grade.

 

[zoebartlett]

Nope, nothing about light performance.

Here's the link: http://agslab.com/reportTypes/pdqr.php?StoneID=8215906&Weight=0.92&D=1

 

[Allison D.]

Zoe, Stonecold is right.....older DQRs didn't give a cut grade, and the new ones assign a cut grade based on parametric grading instead of light performance grading.

 

[zoebartlett]

Thanks Stone-cold and Allison! Why did AGS change their grading system?

So if I wanted to know what cut grade my stone would get, I'd need to send it to AGS? Well, after taking it out of the setting (which I don't want to do)...

 

[slg47]

Thanks Stone-cold and Allison! Why did AGS change their grading system?

So if I wanted to know what cut grade my stone would get, I'd need to send it to AGS? Well, after taking it out of the setting (which I don't want to do)...

I guess you would have to? I'm sure you have done this already but it scores 1.5 on HCA (in AGS0 and GIA Ex zones) and 1A on the AGA cut class system.

 

[stone-cold11]

Thanks Stone-cold and Allison! Why did AGS change their grading system?

So if I wanted to know what cut grade my stone would get, I'd need to send it to AGS? Well, after taking it out of the setting (which I don't want to do)...

Probably to cater for people like you who want a cut grade for their DQR. Market demand.

 

[diamondseeker2006]

Thanks Stone-cold and Allison! Why did AGS change their grading system?

So if I wanted to know what cut grade my stone would get, I'd need to send it to AGS? Well, after taking it out of the setting (which I don't want to do)...

I guess you would have to? I'm sure you have done this already but it scores 1.5 on HCA (in AGS0 and GIA Ex zones) and 1A on the AGA cut class system.

There ya go. That would indicate that it would get AGS0 according to what Allison said if I understand her correctly.

 

[stone-cold11]

Thanks Stone-cold and Allison! Why did AGS change their grading system?

So if I wanted to know what cut grade my stone would get, I'd need to send it to AGS? Well, after taking it out of the setting (which I don't want to do)...

I guess you would have to? I'm sure you have done this already but it scores 1.5 on HCA (in AGS0 and GIA Ex zones) and 1A on the AGA cut class system.

There ya go. That would indicate that it would get AGS0 according to what Allison said if I understand her correctly.

Huh? Where you get that conclusion from?

 

[Christina...]

Thanks Stone-cold and Allison! Why did AGS change their grading system?

So if I wanted to know what cut grade my stone would get, I'd need to send it to AGS? Well, after taking it out of the setting (which I don't want to do)...

I guess you would have to? I'm sure you have done this already but it scores 1.5 on HCA (in AGS0 and GIA Ex zones) and 1A on the AGA cut class system.

There ya go. That would indicate that it would get AGS0 according to what Allison said if I understand her correctly.

Huh? Where you get that conclusion from?

Stone, if she scored a 1A on the AGA cut class, wouldn't that imply that it was an AGS0 or GIA ex? no?

 

[yssie]

Zoe, Stonecold is right.....older DQRs didn't give a cut grade, and the new ones assign a cut grade based on parametric grading instead of light performance grading.

New DQRs w/ light performance analysis for some branded fancy shapes at least - seem to follow DQD grading schema to the T, cut grade max of pol & sym, etc.
http://www.goodoldgold.com/show.php?image=8359/ags.jpg

Don't understand what the difference btwn this new DQR and the DQD is supposed to be?

 

[yssie]

Thanks Stone-cold and Allison! Why did AGS change their grading system?

So if I wanted to know what cut grade my stone would get, I'd need to send it to AGS? Well, after taking it out of the setting (which I don't want to do)...

I guess you would have to? I'm sure you have done this already but it scores 1.5 on HCA (in AGS0 and GIA Ex zones) and 1A on the AGA cut class system.

There ya go. That would indicate that it would get AGS0 according to what Allison said if I understand her correctly.

Huh? Where you get that conclusion from?

Stone, if she scored a 1A on the AGA cut class, wouldn't that imply that it was an AGS0 or GIA ex? no?

No, GIA/AGS DQR (the old one anyway)/AGA all rely strictly on proportions, combinations of proportions. AGS DQD plugs a scan of that specific stone into a ray tracing programme and evaluates the results (can get the printed ASET map too, like on some DQDs, it's a simulation from 90deg just like the handheld/desktop ASET scope) - so a range of crown angles that averages and rounds to a 'nice' 34 that would earn top grade on the proportions-based systems may or may not score so well in the ray tracing simulation, depending on what range of angles there is, how those various areas of the stone interact w/ other proportions, etc. A full scan tells you more, or actual ASET photo/IS if round - the ray tracing programme does not consider effect of inclusions or body colour, we don't know anything about scanning/printing/programming error margins, etc., but it's an extra layer of reassurance if we're otherwise blind.

 

[stone-cold11]

Zoe, Stonecold is right.....older DQRs didn't give a cut grade, and the new ones assign a cut grade based on parametric grading instead of light performance grading.

New DQRs w/ light performance analysis for some branded fancy shapes at least - seem to follow DQD grading schema to the T, cut grade max of pol & sym, etc.
http://www.goodoldgold.com/show.php?image=8359/ags.jpg

Don't understand what the difference btwn this new DQR and the DQD is supposed to be?

Those seems to be special request by the brands, not the general grading report, I have only seen those with branded, specialty cuts. And the report also specifically state that it is a Light Performance based DQR instead of just DQR.

 

[stone-cold11]

AGS DQD plugs a scan of that specific stone into a ray tracing programme and evaluates the results (can get the printed ASET map too, like on some DQDs, it's a simulation from 90deg just like the handheld/desktop ASET scope) - so a range of crown angles that averages and rounds to a 'nice' 34 that would earn top grade on the proportions-based systems may or may not score so well in the ray tracing simulation, depending on what range of angles there is, how those various areas of the stone interact w/ other proportions, etc

From my understanding, a range of simulation angles are used for the DQD, not just the view from the 90deg angle. I remember reading 15 deg tilt.

 

[zoebartlett]

Thanks so much for your replies everyone! I'll read through the thread more thoroughly later tonight, but I appreciate your help. I'm not quite sure why this is suddenly so important to me *now*, considering we got this diamond for my engagement ring 4 years ago. I really like it, I do, but I'm not sure it's the one I really, really want anymore. It's not an H&A stone, as you know, just a "regular" one. Basically, I want something I can't have right now, and it kind of bugs me. Gosh, that sounds snobby! I'm not like that, honest! Plus, I have DSS at the moment, which isn't helping.

 

[Christina...]

Thanks Stone-cold and Allison! Why did AGS change their grading system?

So if I wanted to know what cut grade my stone would get, I'd need to send it to AGS? Well, after taking it out of the setting (which I don't want to do)...

I guess you would have to? I'm sure you have done this already but it scores 1.5 on HCA (in AGS0 and GIA Ex zones) and 1A on the AGA cut class system.

There ya go. That would indicate that it would get AGS0 according to what Allison said if I understand her correctly.

Huh? Where you get that conclusion from?

Stone, if she scored a 1A on the AGA cut class, wouldn't that imply that it was an AGS0 or GIA ex? no?

No, GIA/AGS DQR (the old one anyway)/AGA all rely strictly on proportions, combinations of proportions. AGS DQD plugs a scan of that specific stone into a ray tracing programme and evaluates the results (can get the printed ASET map too, like on some DQDs, it's a simulation from 90deg just like the handheld/desktop ASET scope) - so a range of crown angles that averages and rounds to a 'nice' 34 that would earn top grade on the proportions-based systems may or may not score so well in the ray tracing simulation, depending on what range of angles there is, how those various areas of the stone interact w/ other proportions, etc. A full scan tells you more, or actual ASET photo/IS if round - the ray tracing programme does not consider effect of inclusions or body colour, we don't know anything about scanning/printing/programming error margins, etc., but it's an extra layer of reassurance if we're otherwise blind.

Thanks Yssie! I sometime wonder if I'll ever wrap my head around ALL this information!

 

[yssie]

Zoe, Stonecold is right.....older DQRs didn't give a cut grade, and the new ones assign a cut grade based on parametric grading instead of light performance grading.

New DQRs w/ light performance analysis for some branded fancy shapes at least - seem to follow DQD grading schema to the T, cut grade max of pol & sym, etc.
http://www.goodoldgold.com/show.php?image=8359/ags.jpg

Don't understand what the difference btwn this new DQR and the DQD is supposed to be?

Those seems to be special request by the brands, not the general grading report, I have only seen those with branded, specialty cuts. And the report also specifically state that it is a Light Performance based DQR instead of just DQR.

Makes sense. It's a branded cut special offering.. well, that's how it seems to file itself, at any rate!

From my understanding, a range of simulation angles are used for the DQD, not just the view from the 90deg angle. I remember reading 15 deg tilt.

I actually thought this too, but I believe it was Wink who explained the printed image is just head-on, and that AGS found the effort required to study all the increments through X turned out not to be worth it given the 90deg pic - I'll try and find the post

ETA: found it - I take this to mean that they don't bother taking those readings at the various degrees anymore, but I could be off -

The AGS image on the Platinum report is a computer generated image, but it is the image of that stone from exactly 90 degrees (face up).

When they are doing their research they may take a reading every degree from 0 through 35 degrees from the perpendicular. They have found that when they were finished with the research that in the round if they take a ray tracing at the perpendicular (90 degrees from the table) and another at 15 degrees from the perpendicular they will get readings that are very very close to what they would get doing all the readings, and at a fraction of the time it takes to ray trace 40,000 rays in one degree increments.

So yes, they do actually take readings from more than one angle, but the picture that they print is in fact a static rendering as the stone would look in the ASET at exactly face up.

I know that John Pollard has some videos that show the rotation of the stone through many degrees of tilt. Perhaps he will post them for us here, and as you will see, a composite photo would not look at all like the one on the report.

I had the pleasure of speaking with Peter Yantzer about this as I thought that they took more angles into consideration. He was happy to share with us how they do it now and why, and it made my day just to get to speak with him.

Wink

 

[stone-cold11]

ETA: found it - I take this to mean that they don't bother taking those readings at the various degrees anymore, but I could be off -

The AGS image on the Platinum report is a computer generated image, but it is the image of that stone from exactly 90 degrees (face up).

When they are doing their research they may take a reading every degree from 0 through 35 degrees from the perpendicular. They have found that when they were finished with the research that in the round if they take a ray tracing at the perpendicular (90 degrees from the table) and another at 15 degrees from the perpendicular they will get readings that are very very close to what they would get doing all the readings, and at a fraction of the time it takes to ray trace 40,000 rays in one degree increments.

So yes, they do actually take readings from more than one angle, but the picture that they print is in fact a static rendering as the stone would look in the ASET at exactly face up.

I know that John Pollard has some videos that show the rotation of the stone through many degrees of tilt. Perhaps he will post them for us here, and as you will see, a composite photo would not look at all like the one on the report.

I had the pleasure of speaking with Peter Yantzer about this as I thought that they took more angles into consideration. He was happy to share with us how they do it now and why, and it made my day just to get to speak with him.

Wink

From the bold passage, I take it to mean as they take 2 readings now, 90 and 75 degree, instead of doing 35degrees in 1 degree increment from 90 - 55 degree.

 

[zoebartlett]

Christina -- I've been here for years now and I still can't wrap my head around all the information!

Thanks again everyone!

 

[WinkHPD]

Thanks Stone-cold and Allison! Why did AGS change their grading system?

So if I wanted to know what cut grade my stone would get, I'd need to send it to AGS? Well, after taking it out of the setting (which I don't want to do)...

Actually you can call AGS and inquire. They may have all they need to issue the higher report and charge you a fee based on what you have now. The report will still be dated the same date as the original report.

They may not have the information too, it depends on how old the report is and what information was gathered about the gem.

Wink

 

[denverappraiser]

Thanks Stone-cold and Allison! Why did AGS change their grading system?

So if I wanted to know what cut grade my stone would get, I'd need to send it to AGS? Well, after taking it out of the setting (which I don't want to do)...

Actually you can call AGS and inquire. They may have all they need to issue the higher report and charge you a fee based on what you have now. The report will still be dated the same date as the original report.

They may not have the information too, it depends on how old the report is and what information was gathered about the gem.

Wink

I think that service, when it's possible, is only available to trade members and folks with AGSL accounts. Those aren't all that hard to find, most jewelers and appraisers are able to do it, but I don't think AGSL will work directly with a consumer on this.