Darkness in a cushion modified brilliant?

[kenny]

Inferred from the amount of darkness seen in rounds with known proportions. Whether its 8.0 - 10 inches(it should be in this range) or if it varies slightly isn't the important part, just that it is too close and the lense shadow is so significant as to obscure an estimation of the true brightness and brilliance of the diamond.

On this diamond its closer to 8 inches. http://www.jamesallen.com/loose-dia...arat-i-color-vs2-clarity-ideal-cut-sku-290425

When I say 8 inches its from the middle of the viewer's head to the diamond.

Fascinating.

What is your source for the 3 pics of the three distances?
Are those distances from the diamond to the middle of the viewers head? the camera sensor? or the front of the camera lens?

The pics were not taken with a human head.
They were taken with a camera, and a camera is much smaller than a human head.

Either way, the 3 pics do prove my oft-repeated point ... that the further the camera is from the diamond the less black reflection of the camera will be returned by the diamond.
This supports buying the macro lense with the longest working distance, the 200mm.

 

[gr8leo87]

James Allen photo setup has the camera equivalent to a viewer at around 9 inches away.

I'm not a diamond vendor so I have no dog in this fight but I'm very curious how you know this.
Online diamond vendors know they live or die by their photography so they may consider their photo set ups to be very proprietary.

What is your source for this claim?
Did they tell you?
Did you work there?

Do you have a way to determine that based on what you see in the photos? If so, I love to hear the explanation.
Did you somehow find out the focal length of the macro lens and sensor size they use and what lens extension mechanism and length they use?

Lastly, is that 9 inches from the diamond to the sensor or from the diamond to the front of the lens (or lens hood if used)?
This is important because that distance can differ by as much as 20 inches in my set up.
This is the macro lens, Nikkor micro 200mm f4 that allows the camera to be further away from the diamond than any other lens on the market.
Since greater working distance results in less black reflection in the diamond, I'd think this is the lens the most knowledgeable diamond vendors should be using.
They'd want to experiment with whether or not to use the lens hood though.
It does reduce ghosting but it brings the dreaded black circle 3 inches closer to the diamond ... eating up 3" of the precious working distance you paid so dearly for with this lens.

Hi Kenny.

Agree with the still photography part - with the glamour shots it does indeed look very proprietary. But the videography not so much - or at all.

 

[queradas]

Fascinating.

What is your source for the 3 pics of the three distances?
Diamcalc simulated Images.

Are those distances from the diamond to the middle of the viewers head? the camera sensor? or the front of the camera lens?
Middle of Viewers Head as written above.


The pics were not taken with a human head.
No I beleive it is a simulation with a dark sphere representing a viewer's head, if you want to know more ask Serg.

They were taken with a camera, and a camera is much smaller than a human head.
Yes and no it depends heavily on the depth of the lense and how much shadow it casts on the diamond.

Either way, the 3 pics do prove my oft-repeated point ... that the further the camera is from the diamond the less black reflection of the camera will be returned by the diamond.

Yes and you don't need to be a photography nut to understand this

This supports buying the macro lense with the longest working distance, the 200mm.

 

[Serg]

He Kenny,

for correct comparison head and camera obscuration angles in classical round cut You have to account asymmetries in head obscuration and in ray paths .

for example left, right angles for head obscuration and some main facets have difference in 2.4 times.

for some cut such difference does not work. The difference in left right angle obscuration is very important to create Brilliancy , because such asymmetry create opportunity to see same facet as white in one eye and black in other eye.

 

[Serg]

ray paths for cut with good Brilliancy performance

 

[Serg]

ray paths for cut with less Brilliancy performance but with high brightness