I have owned an SB fluor ideal cut stone and returned it after seeing it in many lighting conditions. Sunlight and some incadescent lighting conditions will give the diamond a blue/violet tint and perhaps make it appear slightly opaque (as any glowing object might) at certain angles.
Under other lighting, the diamond may have even pinkish or greenish soft glow but very white in most lighting conditons (I had a G). In most lighting conditions (containing some UV) it will definitely show up whiter face up and from a profile. Yes, even in the profile view it looks white to slightly blue in incadescent lighting. The G color stone I have now with faint fluor appears very slightly yellow like a normal G from the side.
I don't know if it's due to other variables (the only variable other than fluor bieng proporiton which was nearly the same except for a slightly shallower crown (34.3 versus 34.1), a slightly overall deepness (61.5 versus 60.9), and a slightly thicker girdle (but still medium for both) on a stone without fluor , but the stone with strong fluor had very intense white flashes of whereas the stone with faint fluor was dispersing bold colors and white light like mad in sunlight. In a dark room with point lighting, the SB fluor stone looked exceedingly white sparkly with a dark background (not white as in brilliant but like white fire) wheareas the stone with faint fluor appeared slighly less intensely sparkly with a lighter body color and some fire fire. The SB stone looked darker and more contrasty while the faint flour stone looked brighter and firey (almost no fire in SB fluor). The light leakage of SB stone was also nearly nil whereas the faint fluor stone had some peripheral leakage and slight table leakage (used an ideal-scope). Also, the faint flour stone had more distribution of black spots betwee arrow heads and arrow shafts while the SB fluor stone had only black arrows and smaller black spots between arrow heads, though both were H&A patterns. The color and clarity were the same for both (VS1s with crystals and feathers). Both are AGS ideal cuts with HCA scores 1 and 1.1.
So the bottom line is that it appeared blue/violet in the sunlight that all my buddies could see without dubiety and possibly had less fire. Other factors such as symmetry patterns, leakge patterns, and even the minute proportion differences could have affected fire so judgement on effects on fire are tenous.
My personal opinion is that SB fluors definite blue/violet tint is undesireable if one is wants a colorless stone. If one wants a chameleon, that is another story.
Even the faint fluor stone has some very very pale sky blue (not violet) face up color only in very strong sunlight but it is seems to have no effect on dispersion and blinding light return. I've also read that colorless diamonds naturally appear slightly blue so I can't really say if faint fluor is causing this and from what I've read faint fluor should have no effect. In any case I find this nearly undetectable tint pleasing whereas in SB fluor it's just so very blue/violet which makes it look like a blue/violet diamond.
Loss of transparency is touted rare, so the color in sunlight should be more of a concern for those considering SB or perhaps even med fluor.
