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How much confidence should I put in these Diamcalc
simulated firescope images? Are they accurate?
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A DiamCalc simulated image is only as accurate as the information given it. Also, the symmetry of the image is "excellent", while the symmetry of the subject diamond is probably otherwise. In addition, if the minor facets haven't been corrected, the image could be different than the actual image seen when viewing the diamond.
An actual IdealScope photo is much more reliable than a simulated image, but a simulated image is better than nothing.
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How would you rate the attached image?
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Very good. The person who did the image should be able to supply you with a light return analysis as well, but it looks to my eyes to have something along these lines-
Very good light return
Very good to good non-leakage profile
Very good contrast
Very good non-fisheye effect
That's just off the top of my head eye-balling it, so don't take that opinion to the bank.
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Is that dark ring in the middle a fish eye? Or is
that normal?
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That's just part of the normal reflection pattern. The diamond portrayed would have nowhere near a fisheye effect.
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Are the dark greys in the simulated images
equivelant to blacks in the actual photographs?
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A lot of times this is the case. The relationship between the simulated dark greys and the actual dark greys or blacks is somewhat tenuous.
Overall, if the stone is accurately represented, it should be pretty sharp. As RockDoc points out, further testing is warranted for more objective results.