Article Over Grading of Blue Fluorescent Diamonds Revisited

[sharonp]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Among others, you're assuming Michael is correct about this four grade color shift. Even if we can find a single stone that would move four colors in a colorless, it would by no means be a "textbook case"- rather if it does exist, it would be an anomaly

No Rockdiamond and I don't think you should be putting words in my mouth considering your having trouble reading both Michael's paper and my posts in this thread.

Remember this post made by me » 08 Mar 2016 11:28

"It has been borne out in the empirical data that using GIA's Diamond Dock (its current grading environment) the color shift in the most extreme cases is reduced to 2 - 3 grades, you keep referencing one case using GIA's pre 2000 lighting. The overall conclusion is not dependent on that singular example which is not the normal expected shift for VSB diamonds being graded using today's GIA-GTL diamond dock."

 

[sharonp]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

1) What percentage of all diamonds on offer have VSB?
2) What percentage of all diamonds on offer have SB?
3) What percentage of all diamonds on offer have VSB and are graded with value of DEF?
4) What percentage of all diamonds on offer have SB and are graded DEF?

Rockdiamond and other trade with access to Rapnet I am still waiting on answers to these questions. If you insist on consumers ignoring Michael's paper than tell us how small a percentage of stones could actually be overgraded?

I am actually more concerned about stones with Fluoro that are overpriced.

In 2014 My friend bought a 1.06Ct D VSB Fluoro Oval for $4500. I wonder what its true grade sans UV and VV would have been and if it would have been priced lower or higher had it come back with a true E or F grade from GIA with no mention of Fluoro.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

HI Sharonp,
Lux meter ordered!
Thanks for the suggestion.

Good luck with it, once you have measured Lux from 3 feet from your ceiling lights and also moved the meter close enough to register 2150 lux I think you will be satisfied it is enough light.

Rather than disputing the science what about the market significance of overgrading Fluoro? (Is it really that many diamonds?)
Will you do a rapnet search and pull the answers to these questions:

1) What percentage of all diamonds on offer have VSB?
2) What percentage of all diamonds on offer have SB?
3) What percentage of all diamonds on offer have VSB and are graded with value of DEF?
4) What percentage of all diamonds on offer have SB and are graded DEF?

Got it, and my apologies- it's been a long discussion.
The assumption I had in mind was the one about grading the ability to grade 3 feet from the lamp.
A competent grader would never feel comfortable issuing a grade at 36 inches from the lamp. It would be a guess at best.
You'd need to examine the diamond either in northern light, or closer under a grading light to feel comfortable knowing the color of that diamond.
Sharon- I'm honestly sorry we got off on the wrong foot.
If you are interested in learning from all the participants, it is an interesting discussion.
Although I disagree with aspects of the study, I respect the effort Michael has put in.
The questions you've asked in the post I've quoted above- they are at the heart of the discussion- if we add price.

I'd ask slightly different questions:
What's the average percentage of discount for D-E-F MB/SB stones as compared with inert stones, otherwise identical.
Search is 1.00-1.05 D-E-F VS1 XXX RBC
Using representative numbers
For every 100 inert diamonds there were 30 MB/SB/VST
For every dollar you'd spend on an inert diamond, you'd spend .80cents on you MB/SB/VST diamond.
Based on a sample size of well over 1000 for inert.
My bet is that we'll find much different averages for colors I-J-K.
That's the market adjusting to reality and GIA diamond grades.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

1) What percentage of all diamonds on offer have VSB?
2) What percentage of all diamonds on offer have SB?
3) What percentage of all diamonds on offer have VSB and are graded with value of DEF?
4) What percentage of all diamonds on offer have SB and are graded DEF?

Rockdiamond and other trade with access to Rapnet I am still waiting on answers to these questions. If you insist on consumers ignoring Michael's paper than tell us how small a percentage of stones could actually be overgraded?

I am actually more concerned about stones with Fluoro that are overpriced.

In 2014 My friend bought a 1.06Ct D VSB Fluoro Oval for $4500. I wonder what its true grade sans UV and VV would have been and if it would have been priced lower or higher had it come back with a true E or F grade from GIA with no mention of Fluoro.

Excellent post Sharon.
Does your friend feel that her diamond is not a D when she views in in a way where she can see the color?
Just doing some quick internet retail research, you'll find the price was very low. Even if it was an F/VS1

If she loves the diamond it's a banging deal, no?

 

[sharonp]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Excellent post Sharon.
Does your friend feel that her diamond is not a D when she views in in a way where she can see the color?
Just doing some quick internet retail research, you'll find the price was very low. Even if it was an F/VS1

If she loves the diamond it's a banging deal, no?

If I look for comps today no doubt it was a great deal even compared to the same Oval 1.06 D SI1 with Strong Fluoro. She is very happy with the Ring and the diamond and the glow under black light is cool to her.

You and I both know noone can tell the difference between a D and E or F faceup unless you had them both side by side and even then its not easy. Her husband is happy that its the highest most rare color grade. Its not about what it looks like, its about how it should be priced. The ambiguity is the cause for concern.

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Thank you Sharon. Your thorough reading and understanding of the original 2010 Journal of Gemmology article is edifying to me.

You are welcome, could you please provide some details hopefully this will silence some of the critics:

1) The tubes in Source 7 lighting how did you arrange them 3 feet from the diamonds?
2) Were you using GIA master stones and methodologies when you were grading the 25 diamonds in this study in Lighting 7?
3) What did you use to measure the light intensity at the Tray in Lighting 7 and in the other 6 scenarios? How come you don't have a value for the GIA-GTL lightbox?

4) Do you think that the grade whitening for Strong Blue Fluro (not VSB) between GIA-GTL and Source 7 is significant enough for concern?
7 and 8 (2 Grades)
9 (1 Grade)
10 (2 Grades)
15 (0 Grades)
6 (1 Grade) (Assuming your Source 3 is similar enough to GIA-GTL).

Written by michaelgem » 08 Mar 2016 22:35:

Thank you Sharon. Your thorough reading and understanding of the original 2010 Journal of Gemmology article is edifying to me.

You are welcome, could you please provide some details hopefully this will silence some of the critics:

The goal of all this effort is an informed consumer. If the goal were to silence some of the critics we would be better off joining Don Quixote de La Mancha tilting with windmills.

1) The tubes in Source 7 lighting how did you arrange them 3 feet from the diamonds?

Source 7 was Northern daylight balanced fluorescent lighting mounted in a standard 8ft ceiling. I stood under it holding the tray of diamond masters and the diamond to be graded at shoulder height about three feet from the tubes. At this distance the main difficulty grading is not light intensity, which was more than adequate. It was the quality of the light. Even when you are only 7 inches from the tubes in the DiamondDock reflections and sparkle make it difficult to gauge the body color against the masters. That is why there is a tendency to raise the tray closer to the tubes where the illumination is more diffuse and the body color more discernible, but also where the UV and visible light intensity enhances the color. The solution that worked well for me was to fold white paper in around the diamonds letting the light in from about a quarter inch wide opening. This cut out the reflections and sparkle enabling a good read of the unenhanced true body color.

2) Were you using GIA master stones and methodologies when you were grading the 25 diamonds in this study in Lighting 7?

Yes. It's worth pointing out that I have an article published in the Journal of Gemology, NY Diamond Magazine, Israel Diamond Magazine and the NAJA Quarterly, a section of which is devoted to GIA Diamond grading methodology and lighting.

3) What did you use to measure the light intensity at the Tray in Lighting 7 and in the other 6 scenarios? How come you don't have a value for the GIA-GTL lightbox?

A Dazor Model 5.7 (UVA +B) total UV instrument was employed to measure the amount of UV present in each lighting environment. This meter was calibrated to NIST standards, and measures the UV band from 280–400 nm over a range of 0 to 1999 µW/cm².

Because the visible wavelengths at and below the 415.2 nm, N3-centre in diamond also excite blue fluorescence, it was additionally important to measure the light intensity as a function of the distance from each of the grading lights to explore the visible light's deep violet component’s influence on grading of fluorescent diamonds. Measurements in foot candles of visible light intensity at different grading distances were obtained using a GE Light meter, Type 217.

Because most of the diamonds used in the study had GIA grading reports dated well after 2000 when GIA had switched to the DiamondDock, the grade you see listed for the GIA-GTL lightbox was that listed in the grading report. I did not have access to GIA's DiamondDock to make UV and Visible light intensity measurements like I did at AGSL. There lab director Peter Yantzer kindly allowed me access to their DiamondDock. His top two graders individually graded and provided me reports on all 25 diamonds. This gives anyone interested a unique one-moment-in-time opportunity to compare GIA and AGSL as well as my own grading to see any variability.

4) Do you think that the grade whitening for Strong Blue Fluro (not VSB) between GIA-GTL and Source 7 is significant enough for concern?
7 and 8 (2 Grades)
9 (1 Grade)
10 (2 Grades)
15 (0 Grades)
6 (1 Grade) (Assuming your Source 3 is similar enough to GIA-GTL).

That is a great question, since we have mainly focused on VSB, while STB are more often encountered.

Here is what I was able to conclude from this limited data-base concerning the degree of over grading of strong and medium blue fluorescent diamonds:

Looking at the scatter plot of the ‘Strong Blue’ diamonds #6 to #10 a quite consistent two grade whitening is evident in the unfiltered DiamondLite as well as in the DiamondDock standard Verilux lighting used in the GIA and the author’s grading, compared with the grades obtained in UV-free light. AGSL’s grading of these ‘Strong Blue’ diamonds differed, obtaining on average only one grade of whitening in their DiamondDock lighting.

Judging from this limited sample size, the change in lighting from the DiamondLite to the DiamondDock, while clearly reducing the likely amount of over grading in ‘Very Strong Blue’ diamonds, appears to result in a less consistent reduction in the ‘Strong Blue’ fluorescent diamonds. The same can be said for the less consistent reduction seen in the half to one grade whitening typically seen in the ‘Medium Blue’ diamonds in the unfiltered DiamondLite.

This lack of consistency is likely related to the stated wide allowed range in strength of UV and visible light in the unfiltered Diamond Dock lighting. The light intensity measured at the tray in the AGSL DiamondDock was weaker at 230fc compared to 350fc measured at the same 7inches in the same Verilux tubes (obtained with the DiamondDocks bought from GIA). This is a good illustration of the inevitable inconsistency that results when grading in lighting with fluorescence enhancing amounts of UV and VV.

Note at the end of the pricescope fluorescence revisited article the discussion of lighting standards from King, Geurts, Gilbertson, and Shigley, 2008. Color grading “D-to-Z” diamonds at the GIA Laboratory. Gems & Gemology, 44(4), 296–321:

Although a grading distance of 8-10 inches is specified, the shelf of the DiamondDock enforces a 7 inch grading distance from lamps to grading tray. Because UV and VV vary greatly with distance from the lamps the exact distance is important to establish, because it effectively defines the chosen “standard” amount of UV excitation. GIA researcher Ronald Geurtz (pers. com.) notes an important point about this current lighting standard. The allowed range of light intensity of 2000-4500lux at the surface of the grading tray means the “standard” amount of UV and VV also varies over this same 2.5 times range. Such an allowed large variation of UV and VV defeats standardization of the amount of UV. The variability of UV in fluorescent lighting remains a cause of inconsistency in the grading of fluorescent diamonds.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Michael: would you agree that grading in the way you described is unorthodox to say the least? I'm not talking about the part where you put it in a folded piece of paper – that is common. I'm talking about trying to grade 3 feet from a ceiling light?
In other words have you seen anyone else trying to color grade diamonds standing and holding the diamond up in the air to get it 3 feet away from a ceiling light?

The other thing: the term "peer review" has been used on numerous occasions during this discussion. When color grading, it is common to show the stone to a colleague to get a second opinion, or even a third opinion. Did anyone else color grade the diamond and observe this four grade shift at the time you did your grading study?

 

[michaelgem]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Michael: would you agree that grading in the way you described is unorthodox to say the least? I'm not talking about the part where you put it in a folded piece of paper – that is common. I'm talking about trying to grade 3 feet from a ceiling light?
In other words have you seen anyone else trying to color grade diamonds standing and holding the diamond up in the air to get it 3 feet away from a ceiling light?

The other thing: the term "peer review" has been used on numerous occasions during this discussion. When color grading, it is common to show the stone to a colleague to get a second opinion, or even a third opinion. Did anyone else color grade the diamond and observe this four grade shift at the time you did your grading study?

With all your experience in the diamond trade you undoubtably know the many unorthodox but quite effective grading techniques used in the trade. Typical methods of dealers I know who consistantly nail the grade are to observe the diamond in a folded white business card with or without a GIA graded reference stone right up near the twin fluorescent tubes of the old Dazor swing arm desk lamp or an Ott fluorescent light. They do very well except when grading a fluorescent diamond.

There was nothing unorthodox in my grading except for the lighting. Rather than holding the diamond up in the air, I simply held it in my hand at normal focusing distance from my eyes just as anyone would when looking closely at a diamond ring. In the case of my 6 foot height that put the tray of diamonds roughly three feet from the overhead fluorescent light where there was no measurable UV and 200fc of visible light intensity, so no grade enhancing stimulation of blue fluorescence.

As for your legitimate concern for my color grading ability, recall this paragraph:

Because most of the diamonds used in the study had GIA grading reports dated well after 2000 when GIA had switched to the DiamondDock, the grade you see listed for the GIA-GTL lightbox was that listed in the grading report. I did not have access to GIA's DiamondDock to make UV and Visible light intensity measurements like I did at AGSL. There lab director Peter Yantzer kindly allowed me access to their DiamondDock. His top two graders individually graded and provided me reports on all 25 diamonds.

This gives anyone interested a unique one-moment-in-time opportunity to compare GIA and AGSL as well as my own grading to see any variability.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

To your first point Michael:
Unorthodox methods are not common when it comes to grading in my experience.
If someone is truly interested in the accurate color of a diamond, they would never limit the exposure to a distance of 36 inches from the bulb- and with very good reason. If their money was on the line, they'd want to accurately grade the color, and would move the diamond closer to the bulb.

IN terms of doing this standing up- if that is the unorthodox aspect we are speaking of, ok. Still- if there's a lot of money on the line, a grader will want to sit down and thoroughly examine the diamond for grading.



Regarding the second point about grading accuracy, and a four grade shift.
If you're referring to the .89mq with VST, GIA graded it as F, and AGSL graded it as a G. That jibes with my experience in the market- a one grade difference is relatively common- there are after all, borderline stones.
Was there any independent verification that other graders also perceived this stone as a J?

BTW- comparing GIA and AGSL grading has been done on many occasions, here and elsewhere, so it's not exactly a once in a "unique" thing

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Part of why the discussion has gotten a bit heated over time is the disagreement about variation in color, and when one can distinguish it.
The article was repeatedly sited as "scientific proof" that color improvement is not possible in "normal lighting" due to insufficient UV.
That should not diminish the fact you put tremendous effort into the paper.
Your presence here discussing it is also very positive. Thank you.

I took some more time to analyze the chart on page 46 of your 2010 article.
Putting aside differences of opinion on methodology, and specific results, we basically agree on a few very important aspects:
1) GIA and AGSL are generally close in color grading- a 2 grade disparity is possible- but rare. I attribute this to the inherent difficulty, and subjectivity in color grading.
2) Color grading stones with MB/SB/VST is particularly tricky.
Combine these two aspects - and there's more inconsistencies in lab color grading of fluoro stones- particularly SB/VST.

We draw different conclusions about the effect of this.
Where I think the main emphasis would be, if I was teaching consumers about fluorescence in colorless diamonds is that it's a characteristic that can be desirable, or neutral, and rarely negative, from a visual standpoint. There's no hard fast rules on exactly how an MB/SB/VST stone will look- and there's a few bad ones.

In terms of price, and lab grading, in higher color stones, MB or SB will cause significant discounting- even if the stone is a very desirable one from a visual standpoint.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis



Playing with my nifty new light meter. The lamp is a three bulb- so we should account for that- it's the light right up top.
I agree that 200 lux is sufficient to color grade diamonds.
I had to hold the meter 10 inches from the grading lamp to get 200.
At 36 inches I get 31 lux.
I could certainly guess at the color at 31 lux- but it would be a very wide guess.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Playing with my nifty new light meter. The lamp is a three bulb- so we should account for that- it's the light right up top.
I agree that 200 lux is sufficient to color grade diamonds.
I had to hold the meter 10 inches from the grading lamp to get 200.
At 36 inches I get 31 lux.
I could certainly guess at the color at 31 lux- but it would be a very wide guess.

Try face up with 2 or more non fluoro stones David - see what number of grade differences you can detect - preferably set stones - like what consumers have, since it's them what we's a protectun!
I suspect it will be harder to pick a D from an F than an H form a J.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Hi All,
More: When I did the 200lux picture, it was in my office, which does have windows, but it was not sunny- it was about 4 or 5 in the afternoon. So there was a lot of ambient light.
Doing the same test again at night required me to get the meter even closer- about 6 inches from the bulbs.
This should put to rest the statement that 36 inches from the bulbs is sufficient to see color accurately, and also that a stone graded F/G (GIA/AGSL) will NOT grade like a J, except in rare cases of overt error on the lab's part. I've never seen GIA issue such a large error personally. If we're considering both GIA and AGSL grading, there's literally no chance of such an error on the lab grades.

Bottom line here for consumers, again- there's no issue of overgrading of fluoro diamonds. IN fact, the opposite is true. There's a fair percentage of higher color MB/SB stones that are discounted, by an average of 20% that will show no negative effects whatsoever, and will also grade correctly in normal grading light.
Some of these stones will even look whiter than their inert cousins graded the same color.

I realize these facts are difficult to admit publicly for someone who put a lot of time into this study- and I thank Michael for having the courage to come here to discuss.
But let's please put these issues to rest.

I will do some price sampling of fluoro stones in the I-J-K range to show the difference in market reaction, and also try Garry's test, and report back.

 

[sharonp]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Playing with my nifty new light meter. The lamp is a three bulb- so we should account for that- it's the light right up top.
I agree that 200 lux is sufficient to color grade diamonds.
I had to hold the meter 10 inches from the grading lamp to get 200.
At 36 inches I get 31 lux.
I could certainly guess at the color at 31 lux- but it would be a very wide guess.

You are confusing foot candles and lux. 200 lux is not enough light to grade but 200 foot candles is! 1fc is 10.76 lux.

You either doubt that he had 200fc at the diamonds, or simply don't understand that his lighting was much stronger than yours!
He reported 36 inches away from the diamonds that the intensity was 200fc.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Playing with my nifty new light meter. The lamp is a three bulb- so we should account for that- it's the light right up top.
I agree that 200 lux is sufficient to color grade diamonds.
I had to hold the meter 10 inches from the grading lamp to get 200.
At 36 inches I get 31 lux.
I could certainly guess at the color at 31 lux- but it would be a very wide guess.

You are confusing foot candles and lux. 200 lux is not enough light to grade but 200 foot candles is! 1fc is 10.76 lux.

You either doubt that he had 200fc at the diamonds, or simply don't understand that his lighting was much stronger than yours!
He reported 36 inches away from the diamonds that the intensity was 200fc.

Despite failing in an attempt at a sweeping pronouncement that the 2010 study has no merit, he has succeeded in validating one of the author’s important observations regarding how common it is for diamond dealers to examine their stones very close to fluorescent tubes at distances that actually do activate color masking, thereby giving them a potentially inaccurate read on the color grade of the goods they are looking at (re: type 1A with N3 center blue flurorescence).

If both trade and the labs are going to continue to grade fluoro diamonds within 10 inches of fluorescent tube lights, then all the more reason they should both use UV filters and/or diffusers.

He also seems to be recognizing through observations with the lux meter the concept detailed in the 2010 study regarding how rapidly the light intensity falls away with distance. This is the essential insight that gives rise to my skepticism that fluoro diamonds look whiter in ordinary indoor lighting environments. If he also had a UV meter, he would most likely confirm that corollary to the 2010 study as well.

 

[sharonp]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Thanks for the detailed response: Here are a few follow up questions:

1] The tubes in Source 7 lighting how did you arrange them 3 feet from the diamonds?

Source 7 was Northern daylight balanced fluorescent lighting mounted in a standard 8ft ceiling. I stood under it holding the tray of diamond masters and the diamond to be graded at shoulder height about three feet from the tubes. At this distance the main difficulty grading is not light intensity, which was more than adequate. It was the quality of the light. Even when you are only 7 inches from the tubes in the DiamondDock reflections and sparkle make it difficult to gauge the body color against the masters. That is why there is a tendency to raise the tray closer to the tubes where the illumination is more diffuse and the body color more discernible, but also where the UV and visible light intensity enhances the color. The solution that worked well for me was to fold white paper in around the diamonds letting the light in from about a quarter inch wide opening. This cut out the reflections and sparkle enabling a good read of the unenhanced true body color.

Wouldn't you be reducing the intensity of the light at the diamonds with the paper? Did you measure the 200fc inside the paper with the diamonds or measure it without?

4) Do you think that the grade whitening for Strong Blue Fluro (not VSB) between GIA-GTL and Source 7 is significant enough for concern?
7 and 8 (2 Grades)
9 (1 Grade)
10 (2 Grades)
15 (0 Grades)

Looking at the scatter plot of the ‘Strong Blue’ diamonds #6 to #10 a quite consistent two grade whitening is evident in the unfiltered DiamondLite as well as in the DiamondDock standard Verilux lighting used in the GIA and the author’s grading, compared with the grades obtained in UV-free light. AGSL’s grading of these ‘Strong Blue’ diamonds differed, obtaining on average only one grade of whitening in their DiamondDock lighting.

Judging from this limited sample size, the change in lighting from the DiamondLite to the DiamondDock, while clearly reducing the likely amount of over grading in ‘Very Strong Blue’ diamonds, appears to result in a less consistent reduction in the ‘Strong Blue’ fluorescent diamonds. The same can be said for the less consistent reduction seen in the half to one grade whitening typically seen in the ‘Medium Blue’ diamonds in the unfiltered DiamondLite.

I see some issues which prompted my question, I would say the "reading error" in your samples even with the Medium and Faint Fluoro shows a pattern of 1 grade difference between GIA and AGSL being more common than not.

Diamonds #7 - #10 Comparing the Diamondlite to Diamond Dock there is no grading difference between them except in Diamond #9 with a 1 grade difference. Really no whitening difference between them unlike the VST Blue case.

Further I see that comparing in Diamondlite between filtered and unfiltered there is no difference unlike the VST case.

Now comparing GIA Diamond Dock to your lighting 7 the average difference for the 4 ST diamonds is less than 2 grades difference on avergae.

The key application for this study and in my opinion requires more data points if you had more ST samples would be if you could show at least a 1 - 2 grade whitening effect being consistent for ST fluoro diamonds.

Further one would need to make sure their weren't systematic biases which led to lower color grades all other things being kept the same and this is crucial part is whether your conditions in Lighting 7 were close enough to GIA grading. I think that it would have been more conclusive if you put UV filters into the GIA Diamond Dock(Source 3 Two Verilux Tubes?) and measured filtered and unfiltered and maintained the same environment as actual GIA graders would use.

 

[sharonp]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

If both trade and the labs are going to continue to grade fluoro diamonds within 10 inches of fluorescent tube lights, then all the more reason they should both use UV filters and/or diffusers.

There seems to be a problem here, that Lux meter is showing 200 lux not 2000 lux. If he is saying that he needed to be 10 inches away to get 200 lux than his lights are not strong enough. How many watt bulbs do you have Rockdiamond?

Edit: Meter X10 Problem Solved had to squint at the picture. It is showing 2000 lux not 200.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Thanks for the detailed response: Here are a few follow up questions:

1] The tubes in Source 7 lighting how did you arrange them 3 feet from the diamonds?

Source 7 was Northern daylight balanced fluorescent lighting mounted in a standard 8ft ceiling. I stood under it holding the tray of diamond masters and the diamond to be graded at shoulder height about three feet from the tubes. At this distance the main difficulty grading is not light intensity, which was more than adequate. It was the quality of the light. Even when you are only 7 inches from the tubes in the DiamondDock reflections and sparkle make it difficult to gauge the body color against the masters. That is why there is a tendency to raise the tray closer to the tubes where the illumination is more diffuse and the body color more discernible, but also where the UV and visible light intensity enhances the color. The solution that worked well for me was to fold white paper in around the diamonds letting the light in from about a quarter inch wide opening. This cut out the reflections and sparkle enabling a good read of the unenhanced true body color.

Wouldn't you be reducing the intensity of the light at the diamonds with the paper? Did you measure the 200fc inside the paper with the diamonds or measure it without?

4) Do you think that the grade whitening for Strong Blue Fluro (not VSB) between GIA-GTL and Source 7 is significant enough for concern?
7 and 8 (2 Grades)
9 (1 Grade)
10 (2 Grades)
15 (0 Grades)

Looking at the scatter plot of the ‘Strong Blue’ diamonds #6 to #10 a quite consistent two grade whitening is evident in the unfiltered DiamondLite as well as in the DiamondDock standard Verilux lighting used in the GIA and the author’s grading, compared with the grades obtained in UV-free light. AGSL’s grading of these ‘Strong Blue’ diamonds differed, obtaining on average only one grade of whitening in their DiamondDock lighting.

Judging from this limited sample size, the change in lighting from the DiamondLite to the DiamondDock, while clearly reducing the likely amount of over grading in ‘Very Strong Blue’ diamonds, appears to result in a less consistent reduction in the ‘Strong Blue’ fluorescent diamonds. The same can be said for the less consistent reduction seen in the half to one grade whitening typically seen in the ‘Medium Blue’ diamonds in the unfiltered DiamondLite.

I see some issues which prompted my question, I would say the "reading error" in your samples even with the Medium and Faint Fluoro shows a pattern of 1 grade difference between GIA and AGSL being more common than not.

Diamonds #7 - #10 Comparing the Diamondlite to Diamond Dock there is no grading difference between them except in Diamond #9 with a 1 grade difference. Really no whitening difference between them unlike the VST Blue case.

Further I see that comparing in Diamondlite between filtered and unfiltered there is no difference unlike the VST case.

Now comparing GIA Diamond Dock to your lighting 7 the average difference for the 4 ST diamonds is less than 2 grades difference on avergae.

The key application for this study and in my opinion requires more data points if you had more ST samples would be if you could show at least a 1 - 2 grade whitening effect being consistent for ST fluoro diamonds.

Further one would need to make sure their weren't systematic biases which led to lower color grades all other things being kept the same and this is crucial part is whether your conditions in Lighting 7 were close enough to GIA grading. I think that it would have been more conclusive if you put UV filters into the GIA Diamond Dock(Source 3 Two Verilux Tubes?) and measured filtered and unfiltered and maintained the same environment as actual GIA graders would use.

I assume Michael will respond to your specific questions, but here is a general observation from my perspective. Since we all agree that 1 grade +- is within tolerance should not we be looking more at the trends in the data rather than on a stone by stone basis? And if one acknowledges the trend seen in the study that suggests a grading issue, why would anyone object to eliminating that potential source of inaccuracy? What is the downside of controlling for color masking fluorescence activation in the grading environment?

I think a key piece of evidence that GIA continues to acknowledge the fluorescence can lead to grading errors is the fact that Master stones are prescribed to be non-fluorescent.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Playing with my nifty new light meter. The lamp is a three bulb- so we should account for that- it's the light right up top.
I agree that 200 lux is sufficient to color grade diamonds.
I had to hold the meter 10 inches from the grading lamp to get 200.
At 36 inches I get 31 lux.
I could certainly guess at the color at 31 lux- but it would be a very wide guess.

You are confusing foot candles and lux. 200 lux is not enough light to grade but 200 foot candles is! 1fc is 10.76 lux.

You either doubt that he had 200fc at the diamonds, or simply don't understand that his lighting was much stronger than yours!
He reported 36 inches away from the diamonds that the intensity was 200fc.

I have 3 x 15w Phillips daylight bulbs.
I have a pretty firm grasp on how bright lighting can be. My lamp is about average for the brightness of a diamond grading lamp.
You're not going to be able to get that much light on a diamond from 36 inches away from any sort of traditional fluorescent lamp.
You are correct about 200 lux not being enough light though. AS you noticed there's a a little x10 next to the reading.
SO actually the picture shows the meter reading 2000 lux.

I seriously doubt Michael will defend the reading of J color for a stone graded F/G by GIA/AGSL- the methods described simply won't be acceptable for accurate color grading. But I'm here to read if and when he does.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Playing with my nifty new light meter. The lamp is a three bulb- so we should account for that- it's the light right up top.
I agree that 200 lux is sufficient to color grade diamonds.
I had to hold the meter 10 inches from the grading lamp to get 200.
At 36 inches I get 31 lux.
I could certainly guess at the color at 31 lux- but it would be a very wide guess.

You are confusing foot candles and lux. 200 lux is not enough light to grade but 200 foot candles is! 1fc is 10.76 lux.

You either doubt that he had 200fc at the diamonds, or simply don't understand that his lighting was much stronger than yours!
He reported 36 inches away from the diamonds that the intensity was 200fc.

Despite failing in an attempt at a sweeping pronouncement that the 2010 study has no merit, he has succeeded in validating one of the author’s important observations regarding how common it is for diamond dealers to examine their stones very close to fluorescent tubes at distances that actually do activate color masking, thereby giving them a potentially inaccurate read on the color grade of the goods they are looking at (re: type 1A with N3 center blue flurorescence).

If both trade and the labs are going to continue to grade fluoro diamonds within 10 inches of fluorescent tube lights, then all the more reason they should both use UV filters and/or diffusers.

He also seems to be recognizing through observations with the lux meter the concept detailed in the 2010 study regarding how rapidly the light intensity falls away with distance. This is the essential insight that gives rise to my skepticism that fluoro diamonds look whiter in ordinary indoor lighting environments. If he also had a UV meter, he would most likely confirm that corollary to the 2010 study as well.

Failing who Bryan?
I did not say the study has not merit, rather I question the conclusions reached.
Yes, it's common for successful diamond dealers/cutters to use proper color grading techniques, as opposed to standing 36inches under a light trying to grade- there's too much at stake. If there was a color masking problem the dealer/cutter is going to suffer, so making sure we get an accurate grade is crucial.
If you ever buy diamonds, how do you check the color?

In terms of light falling away, I did notice a large difference in overall lighting- and how much ambient lighting adds.
If I can't see the color ( such as when I was checking after dark) I can't say there's a whitening.
If there is enough light, I can see the color. IN general the ambient light will have some sun, or reflected sunlight.
I don't need a UV meter, I can see what my eyes see.
All that is really less important- tell your customers fl stones can't light up, it's up to you.

But warning of some sort of problem of overgrading with ZERO evidence it exists is a disservice to consumers.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Playing with my nifty new light meter. The lamp is a three bulb- so we should account for that- it's the light right up top.
I agree that 200 lux is sufficient to color grade diamonds.
I had to hold the meter 10 inches from the grading lamp to get 200.
At 36 inches I get 31 lux.
I could certainly guess at the color at 31 lux- but it would be a very wide guess.

You are confusing foot candles and lux. 200 lux is not enough light to grade but 200 foot candles is! 1fc is 10.76 lux.

You either doubt that he had 200fc at the diamonds, or simply don't understand that his lighting was much stronger than yours!
He reported 36 inches away from the diamonds that the intensity was 200fc.

Despite failing in an attempt at a sweeping pronouncement that the 2010 study has no merit, he has succeeded in validating one of the author’s important observations regarding how common it is for diamond dealers to examine their stones very close to fluorescent tubes at distances that actually do activate color masking, thereby giving them a potentially inaccurate read on the color grade of the goods they are looking at (re: type 1A with N3 center blue flurorescence).

If both trade and the labs are going to continue to grade fluoro diamonds within 10 inches of fluorescent tube lights, then all the more reason they should both use UV filters and/or diffusers.

He also seems to be recognizing through observations with the lux meter the concept detailed in the 2010 study regarding how rapidly the light intensity falls away with distance. This is the essential insight that gives rise to my skepticism that fluoro diamonds look whiter in ordinary indoor lighting environments. If he also had a UV meter, he would most likely confirm that corollary to the 2010 study as well.

Failing who Bryan?
I did not say the study has not merit, rather I question the conclusions reached.
Yes, it's common for successful diamond dealers/cutters to use proper color grading techniques, as opposed to standing 36inches under a light trying to grade- there's too much at stake. If there was a color masking problem the dealer/cutter is going to suffer, so making sure we get an accurate grade is crucial.
If you ever buy diamonds, how do you check the color?

In terms of light falling away, I did notice a large difference in overall lighting- and how much ambient lighting adds.
If I can't see the color ( such as when I was checking after dark) I can't say there's a whitening.
If there is enough light, I can see the color. IN general the ambient light will have some sun, or reflected sunlight.
I don't need a UV meter, I can see what my eyes see.
All that is really less important- tell your customers fl stones can't light up, it's up to you.

But warning of some sort of problem of overgrading with ZERO evidence it exists is a disservice to consumers.

This is my point - the fact that the ambient window light made it possible for David to grade the stones shows that there is in ordinary living environments loads of visible violet light and if that is the case, then there will be grade whitening happening.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Further one would need to make sure their weren't systematic biases which led to lower color grades all other things being kept the same and this is crucial part is whether your conditions in Lighting 7 were close enough to GIA grading. I think that it would have been more conclusive if you put UV filters into the GIA Diamond Dock(Source 3 Two Verilux Tubes?) and measured filtered and unfiltered and maintained the same environment as actual GIA graders would use.

Excellent point Sharon. A big oversight in this study.

I am not arguing in favour of VST blues - they really should be screened - and I have seen 2 grade drops.
But I have not seen negative effects in strong and medium blues and I have been selling diamonds for 40 years. And I look hard and ask questions.
Michael has still not attempted to do the tests I have asked. This is peer review, and I am a peer.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Playing with my nifty new light meter. The lamp is a three bulb- so we should account for that- it's the light right up top.
I agree that 200 lux is sufficient to color grade diamonds.
I had to hold the meter 10 inches from the grading lamp to get 200.
At 36 inches I get 31 lux.
I could certainly guess at the color at 31 lux- but it would be a very wide guess.

You are confusing foot candles and lux. 200 lux is not enough light to grade but 200 foot candles is! 1fc is 10.76 lux.

You either doubt that he had 200fc at the diamonds, or simply don't understand that his lighting was much stronger than yours!
He reported 36 inches away from the diamonds that the intensity was 200fc.

Despite failing in an attempt at a sweeping pronouncement that the 2010 study has no merit, he has succeeded in validating one of the author’s important observations regarding how common it is for diamond dealers to examine their stones very close to fluorescent tubes at distances that actually do activate color masking, thereby giving them a potentially inaccurate read on the color grade of the goods they are looking at (re: type 1A with N3 center blue flurorescence).

If both trade and the labs are going to continue to grade fluoro diamonds within 10 inches of fluorescent tube lights, then all the more reason they should both use UV filters and/or diffusers.

He also seems to be recognizing through observations with the lux meter the concept detailed in the 2010 study regarding how rapidly the light intensity falls away with distance. This is the essential insight that gives rise to my skepticism that fluoro diamonds look whiter in ordinary indoor lighting environments. If he also had a UV meter, he would most likely confirm that corollary to the 2010 study as well.

Failing who Bryan?
I did not say the study has not merit, rather I question the conclusions reached.
Yes, it's common for successful diamond dealers/cutters to use proper color grading techniques, as opposed to standing 36inches under a light trying to grade- there's too much at stake. If there was a color masking problem the dealer/cutter is going to suffer, so making sure we get an accurate grade is crucial.
If you ever buy diamonds, how do you check the color?

In terms of light falling away, I did notice a large difference in overall lighting- and how much ambient lighting adds.
If I can't see the color ( such as when I was checking after dark) I can't say there's a whitening.
If there is enough light, I can see the color. IN general the ambient light will have some sun, or reflected sunlight.
I don't need a UV meter, I can see what my eyes see.
All that is really less important- tell your customers fl stones can't light up, it's up to you.

But warning of some sort of problem of overgrading with ZERO evidence it exists is a disservice to consumers.

The 2010 study presents substantially more than "zero" evidence of a grading problem for blue fluoro diamonds. The test diamonds are graded in various grading environments by various qualified parties including the labs. Measurements are taken of the light content in the various devices. There is a clear trend seen in the direction of overgrading that is consistent with higher amounts of UV based on light source and distance.

There are two issues of concern for consumers, although only the first one is addressed in the study. One, the possibility that the diamond has been awarded a higher lab color grade than it's true color - the color that the consumer will be seeing most often. And two, the almost universally touted benefit that blue fluorescent diamonds will actually look whiter than their non fluorescent counterparts in normal lighting (indoors), which appears to be at odds with the science.

I believe it is reasonable and prudent for a consumer to be aware of these issues and to factor them in to buying decisions.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Playing with my nifty new light meter. The lamp is a three bulb- so we should account for that- it's the light right up top.
I agree that 200 lux is sufficient to color grade diamonds.
I had to hold the meter 10 inches from the grading lamp to get 200.
At 36 inches I get 31 lux.
I could certainly guess at the color at 31 lux- but it would be a very wide guess.

You are confusing foot candles and lux. 200 lux is not enough light to grade but 200 foot candles is! 1fc is 10.76 lux.

You either doubt that he had 200fc at the diamonds, or simply don't understand that his lighting was much stronger than yours!
He reported 36 inches away from the diamonds that the intensity was 200fc.

Despite failing in an attempt at a sweeping pronouncement that the 2010 study has no merit, he has succeeded in validating one of the author’s important observations regarding how common it is for diamond dealers to examine their stones very close to fluorescent tubes at distances that actually do activate color masking, thereby giving them a potentially inaccurate read on the color grade of the goods they are looking at (re: type 1A with N3 center blue flurorescence).

If both trade and the labs are going to continue to grade fluoro diamonds within 10 inches of fluorescent tube lights, then all the more reason they should both use UV filters and/or diffusers.

He also seems to be recognizing through observations with the lux meter the concept detailed in the 2010 study regarding how rapidly the light intensity falls away with distance. This is the essential insight that gives rise to my skepticism that fluoro diamonds look whiter in ordinary indoor lighting environments. If he also had a UV meter, he would most likely confirm that corollary to the 2010 study as well.

Failing who Bryan?
I did not say the study has not merit, rather I question the conclusions reached.
Yes, it's common for successful diamond dealers/cutters to use proper color grading techniques, as opposed to standing 36inches under a light trying to grade- there's too much at stake. If there was a color masking problem the dealer/cutter is going to suffer, so making sure we get an accurate grade is crucial.
If you ever buy diamonds, how do you check the color?

In terms of light falling away, I did notice a large difference in overall lighting- and how much ambient lighting adds.
If I can't see the color ( such as when I was checking after dark) I can't say there's a whitening.
If there is enough light, I can see the color. IN general the ambient light will have some sun, or reflected sunlight.
I don't need a UV meter, I can see what my eyes see.
All that is really less important- tell your customers fl stones can't light up, it's up to you.

But warning of some sort of problem of overgrading with ZERO evidence it exists is a disservice to consumers.

The 2010 study presents substantially more than "zero" evidence of a grading problem for blue fluoro diamonds. The test diamonds are graded in various grading environments by various qualified parties including the labs. Measurements are taken of the light content in the various devices. There is a clear trend seen in the direction of overgrading that is consistent with higher amounts of UV based on light source and distance.

There are two issues of concern for consumers, although only the first one is addressed in the study. One, the possibility that the diamond has been awarded a higher lab color grade than it's true color - the color that the consumer will be seeing most often. And two, the almost universally touted benefit that blue fluorescent diamonds will actually look whiter than their non fluorescent counterparts in normal lighting (indoors), which appears to be at odds with the science.

I believe it is reasonable and prudent for a consumer to be aware of these issues and to factor them in to buying decisions.

Hi Bryan, the only proof I see offered is a chart showing 15 diamonds graded by GIA and AGSL- and another 10 graded by AGSL.
We can see that there's one case of a two grade difference, and 7 cases of a one grade difference with GIA less strict than AGSL, and one case of AGSL being one grade softer than GIA on an inert stone.
Five cases of the same grade.
This type of disparity has been known and discussed a lot here on PS.

I don't see how we can accept Michael's grades as scientific proof. Putting aside methodology, as well as Micheal's eye for color, we have only Michael's opinion of that color grade. There's no second opinion.
No matter who is doing the testing, if you're going to try to prove GIA/AGSL are grading incorrectly, you need to have multiple graders corroborate the findings for them to have any sort of weight.
Plus the sample size is far to small to have broad implications.

We know color grading fluoro stones to be tricky. Rightly or wrongly the market has adjusted for this. Buyers of high colors are more likely to be put off by anything with even a slight negative reputation.
To a consumer, the impact can be seen easily without relying on a study.
Look online and see how much less MB/SB stones sell for in D-E-F colors.
What a consumer needs to know is that some of those discounted stones are tremendous values.

On the lower color side (I-J-K-L), consumers will not see as large a discount on fluoro stones- and may in fact need to pay extra.
Again, do your own study and check prices.
The reason is that the market adjusts to these realities- and sometimes these I-J-K stones benefit from the fluoro. Buyers of these colors are going to be less concerned with fl than D-E-F buyers in general. So the sellers can get a higher price because some of the I-J-K stones just look better- over a broad range of lighting environments. At least mine do Bryan And Garry's.
And a whole bunch of other diamond people I know.
I have been trading for along time- I have not seen any disadvantage to the current GIA /AGSL systems, unless you're a cutter. They may have to buy a percentage of fluoro rough, and they may take a bath on it. Consumers win.

There's many other potential problems that are exponentially more likely to be a problem to consumers...like EGL grading.
That's why a false warning of the sort this paper is putting out there is a detriment as opposed to an assist to consumers.

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

The study involves data from 25 diamonds with fluorescence from none to VSB. They are each graded using multiple instruments (light environments) with varying levels of UV/VV. Grading is done by GIA, AGSL and the author. The scatter plot on page 48 shows the results from the table visually. They all agreed almost perfectly across graders and grading environments on the stones with none or faint fluorescence. Divergence in grading (overgrading) started happening as the stones increased in their fluorescent properties combined with light environments of increasing UV content. It was most extreme in stones of VSB graded under the source with the greatest UV readings. In the light source with no UV component all readings either agreed or were within the one grade tolerance.


It seems abundantly clear from this data that there is an undeniable trend suggesting that color grading accuracy would be significantly improved for blue fluorescent stones if they were graded in an environment free of grade whitening levels of UV and VV.

This is not alarmism. This is common sense.

 

[Rockdiamond]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

Bryan- please let's put the data in context:
We have grading which is done by either GIA, AGSL, or the author ( Michael).

You are avoiding my point regarding this data- we can not simply accept Michael's assessment.
The only hard data we have is the grades offered by GIA or AGSL.
Michael's grading would have to to be peer reviewed ( the specific stones color checked by other graders) for it to have meaning here.
IN addition there's real questions about grading methodology.
First we have Michael's methods.
Then we have the fact that GIA does not specify exactly how the color grading is done, or specific UV or intensity levels.
Aside from comparing GIA to AGSL grades, we do not have a scientific comparison.
Real life experience shows us that although there is a variation possible, the market more than makes up for it.
It also shows us that the effect takes place in many viewing environments.
Your diamonds will do this too Bryan, it's not a bad thing.

 

[sharonp]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

If both trade and the labs are going to continue to grade fluoro diamonds within 10 inches of fluorescent tube lights, then all the more reason they should both use UV filters and/or diffusers.

Well if you are going to suggest to use a lexan filter and a diffuser than this 'solution' environment should have been added to the data chart. GIA diamond dock as close to the GIA-GTL grading environment as possible, with the only change being the addition of the diffuser and lexan filter. Without this data and the small dataset, its difficult to prove that Michael's solution will achieve good agreement with GIA-GTL non fluoro stones.

 

[sharonp]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

I have 3 x 15w Phillips daylight bulbs.
I have a pretty firm grasp on how bright lighting can be. My lamp is about average for the brightness of a diamond grading lamp.
You're not going to be able to get that much light on a diamond from 36 inches away from any sort of traditional fluorescent lamp.
You are correct about 200 lux not being enough light though. AS you noticed there's a a little x10 next to the reading.
SO actually the picture shows the meter reading 2000 lux.

I seriously doubt Michael will defend the reading of J color for a stone graded F/G by GIA/AGSL- the methods described simply won't be acceptable for accurate color grading. But I'm here to read if and when he does.

Your experiment while interesting to you, proves nothing to me, and you keep drawing specious conclusions from it.
I don't think you seem to understand that he was using 4X32W larger bulbs and yours were 3X15 watts that is a huge difference. He claims 2150 lux at the tray 36 inches away from the light, a light intensity you could only achieve 10 inches away in your environment.

 

[Garry H (Cut Nut)]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

It seems abundantly clear from this data that there is an undeniable trend suggesting that color grading accuracy would be significantly improved for blue fluorescent stones if they were graded in an environment free of grade whitening levels of UV and VV.

This is not alarmism. This is common sense.

Bryan the red part is wrong. Surly you understand it?
In this photo, a south facing afternoon window is = to a north facing Northern hemisphere window taken with a 415 nm lens filter shows that there is in a room (northern equivalent light) an abundant source of light that Michael's and the GIA's 2013 article prove has a strong whitening effect on N3 centers in the most common fluorescent cape series colorless diamonds.
Why would you state that VV should be excluded?

 

[Texas Leaguer]

Re: Article: Over Grading of Blue Fluorescent Diamonds Revis

It seems abundantly clear from this data that there is an undeniable trend suggesting that color grading accuracy would be significantly improved for blue fluorescent stones if they were graded in an environment free of grade whitening levels of UV and VV.

This is not alarmism. This is common sense.

Bryan the red part is wrong. Surly you understand it?
In this photo, a south facing afternoon window is = to a north facing Northern hemisphere window taken with a 415 nm lens filter shows that there is in a room (northern equivalent light) an abundant source of light that Michael's and the GIA's 2013 article prove has a strong whitening effect on N3 centers in the most common fluorescent cape series colorless diamonds.
Why would you state that VV should be excluded?

Garry,
I do understand your position, and it is the only argument that has any traction from what I can tell. However, I have seen no evidence presented to demonstrate that the VV behaves any differently than the UV in artificial lighting. That is, the intensities drop off so dramatically with distance that in virtually all indoor lighting scenarios there will be insufficient VV to cause grade whitening levels of fluorescence.

Not to put words in your mouth but your argument seems to be --- OK, filtering out the UV in the grading environment makes sense, but leave the VV because it is all around us and fluorescence in diamonds get activated by this light. Therefore, color whitening takes place in everyday lighting scenarios and lab grade should reflect this reality.

The Hainswhang 3D graph shows the effect of the VV component and it aappears weaker than the UV component in its ability to stimulate blue fluorescence. If both fall off equally at distance, then VV is likewise incapable of stimulating grade whitening fluorescence at normal viewing distances away from artificial light sources.

The obvious solution in my mind is to simply increase the grading distance from the light source to the point where UV is eliminated. VV may still be present, but not in sufficient intensity to cause color masking and to therefore introduce grading inaccuracy.