Robbin Brother MSID cut observation and experience

[lanced]

Much has been said about RB bad experience. My wasn''t bad, but I do learn a good lessons from dealing with them when I decided to not go with RB.
As I posted somewhere here our consideration for a stone from RB with MSID cut that RB bragged about. I saw some technical discussions here on this forum, but not much description/experience described. So I thought I would pay back the valuable opinions you guys provided here by describe what I learned about MSID.

MSID is a patented cut exclusively from RB.
- It does sparkle very much like a very good/excellent cut GIA in "HIGH lighting condition". In such condition, lighting is saturated, so you can''t really pin-point the differences.
- Understand that, I told them to turn off all lights (except light coming in from outside). Cover it with my palm. Now, the differences showed. A "GOOD" GIA cut is brigher with bright spot in the center. RB cut is not bright with a DARK spot in the center.
- Now come the tricks:
+ The 1st sale person is new to the job. So he gave me the 2 stones, one is MSID and the other is GIA good. Both held up 4" above the table surface side-by-side. That is when I can spot the difference.
+ The 2nd sale person is more seasoned. He brought in a WHITE-sheet of paper on which he laid various stone for me to see. In that setting, the result is very impressive. The MSID stone is very bright. However, the brightness is not uniform. It''s like a blob of light. The AGS000 stone is not as bright, but the reflection is very uniform from the edge to the center.
+ So why the WHITE sheet of paper, I asked myself then? Apparently, I finally figured out, that the MSID is very shallowed cut (depth 55%, crown 26 degree), so light leaked out to the bottom. The white sheet reflected the light back, so no loss of light. However, since the reflected light is not controlled (angle), hence the non-uniform reflection.

I checked it today with the HCA analyzer. The MSID stone is way out of range since the crown is too small in degree.

That said, I''m not surprised that some people would buy it believing it''s better cut. Just like a photograph. Some people think the "over-exposure" photo is better because it''s bright. Knowledgeable people think it''s suck because you lost all the detail in the photos.

Anyhow, a few things I learned along the way that I would like to share.

 

[Lorelei]

Thank you for that excellent comparison Lance, most helpful!

 

[Garry H (Cut Nut)]

HCA goes down to 28 degrees.

What you can do is SUBTRACT 0.4 degrees from the pavilion angle that you have and input the 28 degrees.
This will compesate.

The biggest risk though is chipping in these stones. If I were an insurance company i would not accept the risk in less than 8 prong settings

 

[strmrdr]

the problem with a lot of these types of designs is that they only work well over a very very narrow range of proportions.
They do few models that work then put them into production and the then start moving them out of that range for weight retention or the cutting house cant keep the necessary control of the pavilion facets.
Then you end up with junk.

The level of precision needed goes up tremendously once you get outside of the mainstream cuts and very few cutting houses can consistently produce that level.

poor modeling, poor design, poor production precision and a ton of marketing then they wonder why they fail.

In other words they need to hire me or someone like me to do design verification, production planning and target building then hire the best cutting house they can find to cut them and maintain a very strict QC department with a feedback loop to the designers and cutters.