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(This discussion moved from Talk:Diamond).

Contents 1 Is clarity grading done using a standard distance from eye-to-stone? 1.1 How clarity is judged 1.2 Various "answers" 1.3 "Eye clean" vs. Imperfect 1.4 What is 10x relative to? 1.5 A couple of tangents 1.6 History of clarity grade development 1.7 Deletion of EL's

[edit] Is clarity grading done using a standard distance from eye-to-stone?

[edit] How clarity is judged

Diamond clarity is graded on a scale from FL (flawless) to I (imperfect). The standards for each grade are based on how "obvious" or "difficult" it is to see imperfections at various magnifications, such as 1x (with the naked eye), 10x, or 30x. While on-line brochures give the magnification, they do not specify the distance between the eye and the stone. Is this 3"? (Probably not -- many people cannot focus this close.) Is this 6"? (Similar problem.) 14"? 15"? 21? Note that there is 3x magnification between 7" and 21".

Do any of the major grading labs (such as GIA, AGS, or HRD) have a standard on this? For that matter, several U.S. Military specifications (such as for surface defects in ceramics) have similar wording. Do the mil specs have a standard eye-to-object distance?

As far as I know, no. While I don't work for any of the labs you mention, I think I would have heard about such a standard. Nowadays most labs use custom microscopes for grading stones, so "distance to eye" doesn't come into play. A grader has to be careful not to scratch the objective lens with the stone, of course.

When a loupe is used, both it and the diamond are usually held fairly close to the eye as a matter of practice. When checking the stone with the naked eye (especially in unclear cases to judge whether an inclusion justifies a grade of I1 as opposed to SI2) a grader's astigmatism (or lack thereof) will determine distance from the eye. Although I'm fairly myopic and therefore I might be able to see closer, if I can see the inclusion the stone is automatically graded at least I1. (Visible to the eye means visible to the eye.) Some labs may assign an SI3 grade in debatable cases, but of course not everyone recognizes this grade.

Some labs are looser than others when grading stones, but that's not something I should get into here. I try not to be a mudslinger. ;) -- Hadal 04:30, 3 May 2004 (UTC)

I realize that this thread is a few years old, but I think a major misunderstanding is apparent here. Clarity grading has VERY LITTLE to do with eye-cleanness. Clarity grading has everything to do with what the stone looks like under 10X magnification. Eye-cleanness can occur in the I1 (a stone that has a very extensive cloud may not be apparent to the eye - but still be graded I1), an large emerald cut diamond with a small solitary EYE-VISIBLE inclusion in the corner of it's table, may still be graded VS2. Eye-visibility should never be used as a defining criteria for clarity grade. With this in mind, the distance to the eye is irrelevant. SauliH 21:03, 4 February 2007 (UTC)

[edit] Various "answers"

A few web sites address this question. They give various answers.

• Bellman Jewelers states that "I-1 I-2 I-3 (Imperfect)" diamonds "have inclusions that are eye-visible, viewed from the top (6 to 8 inches away)."

• One post at PriceScope mentions 18 inches (for viewing the culet with the naked eye).

• In a contentious 2002 thread on DiamondTalk (which is partly archived), an appraiser is quoted as saying, "Examining the stone loose for seeing unaided eye visible inclusion require the stone only being examined in the face up position approximately 15 inches from the eye and held in such a way that the table is perpendicular to the viewer's eye."

Many microscopes have distances of 14-24 inches from eye-to-stone. Each microscope has a consistent distance for best viewing.

Heh, well.. as you can see, nobody can agree and there is no standard. I personally think both 18 and 15 inches is ridiculous. In the contentious DiamondTalk thread you linked to above, the buyer was clearly cheated. I can't believe someone would try to pass that stone off as anything better than an I1. (I can believe it, but you know what I mean.) I might have been meaner and went to I2, as a feather that large could conceivably affect the integrity of the stone itself.

Of all the links above, Bellman's would come closest to reason. There can't really be a standard, as human eyesight is so variable.

[edit] "Eye clean" vs. Imperfect

That said, I did chuckle at this line from their site:

"Without the proper instruments and education on what to look for, consumers can easily misread a diamond’s clarity."

That may be true of the upper grades, but a savvy consumer should have no trouble spotting an I1, as the fellow in that DiamondTalk thread did. In my rather cynical opinion, I think sellers who use half a yard stick (for crying out loud!) to determine "eye visible" are trying to pass inferior stones off at higher prices than should be paid for them. And that bit about the culet was misinformation. A "medium" culet will detract from the final grade of the stone, or at least it should. As would a lack of culet in a large stone.

[edit] What is 10x relative to?

As for your comments on the microscopes, of course there is a consistent distance for best viewing. I don't think I understand what you're asking; maybe I'm daft, but how can a standard distance be applied to microscopes in this case? There are no great differences in the length of the optical train in the various models used (I've used at least three different makes). The distance from the stone and the objective lens would be determined by the magnification level. The only feature a microscope must have is a 10x setting (and, to be thorough, overhead lighting and darkfield illumination). Or am I missing something? -- Hadal 14:20, 10 May 2004 (UTC)

Hadal, thank you for your straight answers. And no, you're not daft -- indeed, you have helped me clarify my thinking.

"Or am I missing something?"

I am trying to get at -- "What is 10x relative to?"

• If you look through the microscope without the 10x lens in place, you will see the stone at 1x at a distance equal to the length of the optical train.
• If you look through the microscope with the 10x lens in place, you will see the stone at 10x at the same distance.
• Although I do not have access to a microscope, I remember the 10x-20x-30x microscopes used in several applications having very similar lengths of their optical trains. I remember it being somewhere between 14-24 inches, but cannot remember more exactly:
  • High school biology classes
  • Inspection of ceramics per U.S. Military specifications
  • Jewelry stores
• With a 10x loupe the focal point is 2.54 cm (one inch)

[edit] A couple of tangents

The current debate about cut-grading standards involves explicit assumptions about lighting and the distance at which a diamond is viewed. The choice of 10 inches versus 14 inches explains some significant differences between two proposed grading standards, according to this PriceScope thread.

By the way, the stone in the contentious DiamondTalk thread was graded by the AGS as an SI2. Perhaps large SI2 stones do not need to be eye-clean?

-- Jasper 20:15, 14 May 2004 (UTC)

[edit] History of clarity grade development

I have been looking for references to the history of the development of clarity grading which I have read somewhere - especially the GIA system. I am sure it was online. Does anyone know a link to this, as it would greatly help to expand this article. Other subjects that should find mention here is that the GIA system was developed for trade use (especially in the DZ color grade system). I wish I could find the source I need for this, it is not in my GIA course material, but I remember reading it somewhere. SauliH 15:48, 7 December 2006 (UTC)

[edit] Deletion of EL's

The removal of links to the websites of EGL, GIA seems add. Gwernol asserted that these violate WP:EL policy, but has not given a reason why he removed after a revertion was made. Please explain. SauliH 15:51, 7 December 2006 (UTC)

• Since there was no reason given for this removal, wouldn't it be appropriate to restore them given that nobody else objects here? T.E. Goodwin 05:02, 17 February 2007 (UTC)

• • Taking a second look it was only a link to EGL that I could rightfully object to it's removel. The GIA link was not directly to GIA, but on a spam page. The EGL link could rightfully be restored though. SauliH 05:50, 17 February 2007 (UTC)