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Is This Obstruction?

Discussion in 'RockyTalky' started by mlewisii, Dec 14, 2015.

  1. mlewisii
    Rough_Rock

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    by mlewisii » Dec 14, 2015
    Can someone tell me if this dark ring is obstruction? Could it be leakage? I am unable to get an Idealscope/ASET image from JA, due to the work load that they have, at this time. The photo attached is from the site, that I took from the revolving clip, that JA offers. I have done some looking around online, but can't get a definitive answer, as to what I am seeing. Please take a look at the image and numbers below, and let me know if something stands out. As always, I appreciate all input. (The mounting will be a four prong 1.5mm solitaire.) If it is too deep, shallow, bad angles, etc., please explain.

    0.91 ct. H VVS2 GIA Triple Ex.
    58% Table
    61.1% Depth
    34.5 deg. CA
    41 deg. PA
    14.5% Crown height
    43% Pav. depth
    Stars 50%
    LGH 80%
    Med Girdle (3.5%)
    Fluorescence - Faint
    HCA - 1.9



    smartselectimage_2015-12-14-12-51-17.png
     
    


    


  2. kenny
    Super_Ideal_Rock

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    by kenny » Dec 14, 2015
    Common question here on Rocky Talk.
    I just answered this yesterday so I'll repost this ...

    The black we often see in diamond pics, especially those taken head-on, is just a reflection of the black camera and lens.

    The black is not in the diamond any more than a black camera appearing black in a mirror indicates anything is wrong with the mirror.
    Both the mirror and the diamond are just obeying the laws of physics and optics by reflecting what's in front of them.

    The most effective way to reduce black in diamond pics is rarely employed because it is so expensive ... a better lens.
    Using the least-expensvie macro lenses results in more black reflecting in the diamond than the most-expensvie macro lenses.
    Why?
    Macro lenses with shorter focal lengths, like 50 mm, have to be almost kissing the diamond.
    Lenses of longer focal length, like 180 or 200 mm, can be almost a foot away while still delivering the same enlargement.
    Then why doesn't everyone use a 200mm?

    A 200mm Nikon macro lens is $1800.
    http://www.kenrockwell.com/nikon/200mm-micro.htm
    ... but a 40mm Nikon Macro lens is only $280.
    http://kenrockwell.com/nikon/40mm-f28.htm

    When the big black camera is further from the diamond less of it will be reflected by the diamond.

    Here's another thing that I, as a photographer, do to reduce the amount of black that appears in my diamond pics.
    I reduce how much of the black camera that the diamond can "see" by cutting a hole in a white sheet of styrofoam that fits tightly onto the lens.
    Then the diamond "sees" only the lens, not the big black camera.

    screen_shot_2015-12-14_at_10.png

    screen_shot_2015-12-14_at_0.png
     
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  3. mlewisii
    Rough_Rock

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    by mlewisii » Dec 14, 2015
    Thank you Kenny.

    What do you guys think of the numbers, on this diamond?
     
  4. Diamond_Hawk
    Brilliant_Rock
    Trade

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    by Diamond_Hawk » Dec 15, 2015
    As ever, great post and nice images Kenny :clap:
     
    


    


  5. kenny
    Super_Ideal_Rock

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    by kenny » Dec 16, 2015
    Thanks DH. :wavey:

    Nice to hear someone appreciated one of my tiresome, technical, and geeky photography posts.
    I usually feel like a lone voice in the wilderness, an unwashed madman with matted hair and a scraggly beard wandering around mumbling nonsense to myself.

    It never ceases to amaze me how such an integral subject to diamond marketing, Macrophotography, is not only so poorly understood here on PS but that there is virtually no interest, curiosity or participation in discussions about it.

    I can't blame TV for this one, but I can blame those seductive and ubiquitous smartphones. ;-)
     
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  6. solgen
    Brilliant_Rock

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    by solgen » Dec 16, 2015
    The dark ring obstruction or clustering around the inner arrow shafts is due to the proportions. As I understand it's the star facets reflecting in the lower girdle facets. Pavilion angles of 41 along with LGH of 80% seem to exacerbate this. If you stick with a 40.6 pav and 75% LGH and star of 50% you should minimize if not avoid this clustering.
     
  7. mlewisii
    Rough_Rock

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    by mlewisii » Dec 16, 2015
    I got a nice price on this one, from JA, and it is supposed to arrive in a couple of days. I'll be able to fully inspect it, when it comes in. Do you guys have any sample images of more 41 PA with 80% LGH, for me to compare it to? Should I be concerned with light performance? Any and all help/tips/pointers, are greatly appreciated.
     
  8. kenny
    Super_Ideal_Rock

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    by kenny » Dec 16, 2015
    I assume you are referring to this black between the arrow shafts.



    I'm not arguing with what you wrote about changing diamond proportions reducing that black.
    I'm not cut-educated enough to say diamonds with no black between arrow shafts are better cut ... but I'm aware that judging cut by black seen is misleading ...

    Again the black is just reflection of the black camera.
    Diamonds can do amazing things with light but they can't do magic by manufacturing black out of thin air.
    Anything you see in a diamond picture has to be a reflection of something in its environment.
    To photography a diamond is a complex little box of mirrors.
    If the camera body was red some of what usually appears black would appear red.
    (The diamond, however, will always see the lens' glass itself as black.)

    Sure, changing a diamond's proportions/angles moves some of the many mirrors that result from putting 57 facets on a diamond.
    Move a mirror and it will reflect something in a different location in its environment.
    That doesn't make it a better or worse mirror.
    It just changes what location of the camera results in maximum ore minimum black reflections.

    Basically two main things determine the amount of black in pics:
    1. Distance from diamond to camera (and size of black camera, which can be reduced using the white board I showed above). Using a longer lens to get a pic to show less black does not improve the light performance of the diamond, though customers may like the pic better.

    2. Diamond proportions. Changing diamond proportions to reduce black seen in a particular camera set up also does not necessarily mean the diamond has better light performance.
    It just means those diamond proportions no longer favor reflecting the black camera that happens to be located at that particular distance from the diamond because of lens choice.

    Even if you both optimized lens choice and diamond proportions to minimize black the black would return if you moved the camera closer or further from the diamond.

    Disliking diamond pics with black just means the disliker has yet to be informed about this aspect of photography.

    I cringe when I hear prosumers here steer people away from diamonds because of black in pics.
    That means I cringe often.
    I also feel sorry for vendors who unfairly lose sales because of it.

    screen_shot_2015-12-16_at_11.png
     
  9. flyingpig
    Brilliant_Rock

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    by flyingpig » Dec 16, 2015
    Thank you kenny. Always appreciate your inputs.
     
  10. mlewisii
    Rough_Rock

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    by mlewisii » Dec 16, 2015
    Thank you Kenny, that was very helpful. Both of your post's have made me feel much better about my purchase.

    I guess what I'm looking for now, is some more feedback on the diamonds proportions. I have done a lot of reading, and it seems like I should be within the range of a nicely cut stone. But, I have also read some bad topics too. I'm just looking to get some reassurance, that I purchased a nice looking diamond. I do realize that MY eye test will be a deciding factor. Do any of you see any bad numbers on this diamond, that might make it a "trainwreck", when it comes to light performance?
     
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  11. solgen
    Brilliant_Rock

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    by solgen » Dec 16, 2015
    Yes.

    I'm not implying it leads to a better cut of light performance just a different one. IMO it's quite the subjective matter whether or not it's better.

    I will slightly disagree with you here. Changing the angle or proportions of the mirror(s) can have a dramatic effect and adversely affect light performance. Afterall that's why we've established cut grades are why we pay attention to the proportions. You could eliminate black reflections by having a leaky pavilion but that would hardly qualify as a well performing diamond. I understand you're saying not to fear the black reflections as you elaborate below and I agree with that.

    I doubt the further you move something away the more obstruction it would create and return more black. But #2 is what I'd like to key on it. The proportions can change the distance at which the obstruction occurs. So say a 41pa and 80%LGF induce obstruction from 0-18" away. A 40.6PA and 75%LGF induces obstruction from 0-4" away. Thus when viewing it on your finger you may never really notice the obstruction with the latter proportions. As such it can change contrast and scintillation patterns. Doesn't mean it's any better but just that it's different. And the changes might be so minute that it will be lost upon the casual observer.

    I concur. Photography and even videos are making a representation at a particular or limited view of a diamond and should be taken with a grain of salt. Hence why people here tend to always recommend viewing a stone in person under the vast variety of conditions and pass judgment accordingly rather than under the quite limited scope of an image or video.


    mlewisii there are a variety of tools(HCA, reflector images, GIA or AGS proportions, etc) that assess cuts to find those that deliver light performance that is deemed to be superior or perhaps most appealing. Within this there are variations that lead to different contrast or scintillation patterns that may be so minute you might not even notice it. These latter qualities can be quite subjective hence why we also have different types of cuts to appeal to differing perceptions. The cut/performance grades for those that are available help to ensure these qualities are present and thus it becomes find the patterns that appeal to you if you an even discern them.
     
  12. kenny
    Super_Ideal_Rock

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    by kenny » Dec 16, 2015
    Thanks.
    The HCA is under 2.0 so it would be time for Step 2, an Idealscope pic, but.
    Besides just the 'score' HCA also delivers four other categories of performance:



    It is rare to find a diamond that the HCA gives four Excellents to but it's also rare for one that scored under 2.0 to get only one Excellent.
    Most get Ex for everything except Spread.
    Frankly, I'd keep looking since your are shopping for the most common shape, round.
    If you'd like to keep it I'd get an Idealscope pic or buy your own Idealscope.
    https://www.pricescope.com/tools/ideal-scope

    Compare to this chart and/or post the Idealscope image here on PS.

    http://ideal-scope.com/reference-chart-ideal-scope-images/

    screen_shot_2015-12-16_at_2.png

    idealscope_7.png
     
  13. kenny
    Super_Ideal_Rock

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    by kenny » Dec 16, 2015
    Here's why you need an Idealsope image.

    The creator of HCA, Garry Holloway, describes it as a rejection tool, not a final selection tool.
    Why?
    Because the HCA uses data that may not be so groovy.
    The Crown and Pavilion angles it uses, from the lab report, are actually averages of each angle around the 8 sides of the diamond.

    Even if the lab report gives a pavilion angle that is wonderful, say 40.8, it's still only an average of 8 angles.
    Some of the 8 angles could be high and others low, but they happen to average out to 40.8.
    If so that 40.8 is misleading.

    Such wonkiness would be invisible to the HCA but will be revealed by an Idealscope.
     
  14. mlewisii
    Rough_Rock

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    by mlewisii » Dec 17, 2015
    Thank you all! I really appreciate your information. It was very helpful!

    As for the slight asymmetry, I will see if it's too noticeable once I get it. I'm also taking it to a trusted jeweler, to evaluate and appraise it. The only reason I didn't buy from them, was the great price on JA.
     
  15. FearlessSmile
    Rough_Rock

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    by FearlessSmile » Apr 7, 2019
    8C7804C0-461F-4139-B2DE-2F978B2F39C8.png 9509C734-723B-44E4-857D-54AF47A96F84.jpeg Can anyone advise if this is likely to be camera obstruction? Thank you.
     
    


    


  16. lovedogs
    Ideal_Rock

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    by lovedogs » Apr 7, 2019
    You are more likely to get answers on your own thread.
     
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  17. flyingpig
    Brilliant_Rock

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    by flyingpig » Apr 7, 2019
    The camera is too close.
     
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  18. gm89uk
    Brilliant_Rock

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    by gm89uk » Apr 8, 2019
    @FearlessSmile yes the camera is too close and there is consequently a ring of obstruction. Despite that and the tilt, there is asymmetry at 3 o'clock which will likely be leaky. That may or may not bother you.

    Doesn't matter how many times you ask, it is what it is.
    Already discussed here:

    https://www.pricescope.com/community/threads/does-this-formula-work.248092/#post-4526630
    https://www.pricescope.com/community/threads/does-this-formula-work.248092/#post-4526673
    https://www.pricescope.com/community/threads/does-this-formula-work.248092/#post-4526831
     

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