How much of a problem can 40.6 be?

[Kim N]

I'm considering a recut with a 40.6 average pavilion angle (and 34.6 crown), but the cutting will be done to a tolerance of 0.2, which means that some of the pavilion mains may be at 40.4 or 40.5. How much of a problem can this be in terms of obstruction?

 

[Karl_K]

There is a big jump at aprox. 40.45 you want to idealy keep all the mains over. If the lgf% is 77 or over sometimes one or 2 slightly under is not a huge issue but less than ideal.

 

[Kim N]

Thanks, @Karl_K. So it sounds like I'll probably want to keep it to 40.7 average to avoid any of the mains going under 40.45. LGF is around 70%.

 

[Karl_K]

Thanks, @Karl_K. So it sounds like I'll probably want to keep it to 40.7 average to avoid any of the mains going under 40.45. LGF is around 70%.

yea sounds good

 

[Garry H (Cut Nut)]

Generally if there is a variation in pavilion angle - there is a complimentary variation in crown angel and it is less of an issue, or no issue at all.
I personally prefer 40.6 and 34. The only people who would not are short sighted and look at diamonds from crazy close up.

 

[Karl_K]

Generally if there is a variation in pavilion angle - there is a complimentary variation in crown angel and it is less of an issue, or no issue at all.
I personally prefer 40.6 and 34. The only people who would not are short sighted and look at diamonds from crazy close up.

Its arguable one way or the other......
Except its being cut with 70% lowers if ones of those dip to 40.4 your going to see it.

 

[Kim N]

Generally if there is a variation in pavilion angle - there is a complimentary variation in crown angel and it is less of an issue, or no issue at all.
I personally prefer 40.6 and 34. The only people who would not are short sighted and look at diamonds from crazy close up.

Unfortunately, I'm pretty near-sighted and do look at diamonds close up.

 

[Karl_K]

What table size are you having it cut to?

 

[Kim N]

What table size are you having it cut to?

55%

 

[Karl_K]

Unfortunately, I'm pretty near-sighted and do look at diamonds close up.

With the big arrows from the 70% lgf its going to be very contrasty up close no matter what the pavilion angle is cut to.

 

[Karl_K]

40.7 at ~8 inches.



40.4 would be that dark at 15+ inches and beyond where you cant distinguish the arrows as arrows and it just looks dark.

 

[Kim N]

40.7 at ~8 inches.

Wow, thank you for modeling this. I think I'd be very happy if it looked like this at ~8 inches. Knowing there's a tolerance of 0.2, would you expect to see any leakage with 40.7 average?

 

[Karl_K]

Wow, thank you for modeling this. I think I'd be very happy if it looked like this at ~8 inches. Knowing there's a tolerance of 0.2, would you expect to see any leakage with 40.7 average?

no more than is present in any round.

 

[flyingpig]

54/34.9/40.5 76 LGH
I am sure some PAs dip to 40.4

Contrasty, Yes
Darkness or Obstruction Issue IRL, No

 

[Karl_K]

54/34.9/40.5 76 LGH
I am sure some PAs dip to 40.4

Contrasty, Yes
Darkness or Obstruction Issue IRL, No

to much obstruction to make that call.
The issue is mains staying dark under less obstruction instead of going bright.