The link doesn't seem to be working for me http://www.gia.edu/pdfs/Fall_2001_Cut.pdf
teobdl|1373420005|3480009 said:Yeah, the link wouldn't work for me either... but it is the correct URL! Just google "GIA fall 2001 fire," and it's right there.
It's a very good article to complement the one from AGS. Thanks, TL!
Both articles got me thinking...
1. It seems as though Tolk's choice of P40.75 C34.5 actually did NOT maximize light return for his presumed LGF and table! Given his LGF of 50-60 and very small table maximum light return would be "steep deep"--in fact, it probably hits exactly where the AVR is cut (a little over 41 pav, a little over 35 crown).
2. Why has the Tolk pav crown combination stayed so popular? There is another combination that would perform pretty similarly in overall (at least in fire, brilliance), but is much spreadier:
Pav: 38
Crown: 25
Table: 53
LGF: 78
Star: 55
I don't know if all those align exactly, but you get the point. The character would be a little different, but I'm sure there's a market for people who want a huge spread and still very good to excellent light performance (at least in theory).
Coming up with a combination that has slightly higher total light return aka brightness than tolk in some light conditions is easy.teobdl|1373420005|3480009 said:2. Why has the Tolk pav crown combination stayed so popular? There is another combination that would perform pretty similarly in overall (at least in fire, brilliance), but is much spreadier:
Pav: 38
Crown: 25
Table: 53
LGF: 78
Star: 55
teobdl|1373420005|3480009 said:Yeah, the link wouldn't work for me either... but it is the correct URL! Just google "GIA fall 2001 fire," and it's right there.
It's a very good article to complement the one from AGS. Thanks, TL!
Both articles got me thinking...
1. It seems as though Tolk's choice of P40.75 C34.5 actually did NOT maximize light return for his presumed LGF and table! Given his LGF of 50-60 and very small table maximum light return would be "steep deep"--in fact, it probably hits exactly where the AVR is cut (a little over 41 pav, a little over 35 crown).
2. Why has the Tolk pav crown combination stayed so popular? There is another combination that would perform pretty similarly in overall (at least in fire, brilliance), but is much spreadier:
Pav: 38
Crown: 25
Table: 53
LGF: 78
Star: 55
I don't know if all those align exactly, but you get the point. The character would be a little different, but I'm sure there's a market for people who want a huge spread and still very good to excellent light performance (at least in theory).
Karl_K|1375111563|3492447 said:Interesting discussion.
My opinion from real world and DC observations is that the c/p combination can effect the range of light conditions a diamond shows fire. Garry is right there.
However the lower halves have to match the c/p angle combination for it to work in my opinion.
When you get to the extremes or specialized combos small changes in the lower halves have a much greater effect than in a near tolk in my opinion.
Particularly when pavilion angles get below 40.5 degrees small changes in the lowers can make the difference between a diamond with a nice balance of contrast and one with an overly dark table from obstruction.
So while hca can identify possible combinations that show the effect of showing fire more of the time it is not a sure answer and more investigation/information is needed in my opinion.
Fun reading this thread (brings me back a few yearsGarry H (Cut Nut)|1375143729|3492786 said:Karl_K|1375111563|3492447 said:Interesting discussion.
My opinion from real world and DC observations is that the c/p combination can effect the range of light conditions a diamond shows fire. Garry is right there.
However the lower halves have to match the c/p angle combination for it to work in my opinion.
When you get to the extremes or specialized combos small changes in the lower halves have a much greater effect than in a near tolk in my opinion.
Particularly when pavilion angles get below 40.5 degrees small changes in the lowers can make the difference between a diamond with a nice balance of contrast and one with an overly dark table from obstruction.
So while hca can identify possible combinations that show the effect of showing fire more of the time it is not a sure answer and more investigation/information is needed in my opinion.
Agreed Karl,
And in a perfect world I would add this as a factor into HCA, but the lab rounding is even worse.
Lower girdles are also affected by table size.
An old article on http://ideal-scope.com/3.manuf_fine_tuning.asp
If I understand your question correctly, I witnessed mostly LGF's on rounds in the 80% length area.Garry H (Cut Nut)|1375224834|3493318 said:What do you all think are the most commonly encountered LG's and star facet %'s? Means or medians I guess.
What are the extremes at say the stats outlyers that encompass 80% of what you see?