Keep in mind that clarity ratings involve all different kinds of inclusions, carbon, needles, clouding, etc. The cut can also do a great deal for a lower clarity stone, but honestly I've never seen a GIA or EGL or whatever true certified stone SI1 or 2 and better look anything but eye clean. The ratings are based on what is visible under magnification not the naked eye. I've seen I1 stones that look eye clean because cut so well and good color. As for color, I've always been told stones are graded for color by looking at them face down, you see the color on the back of the stone...... Anyway I also think that if you buy non-certified stones there is a great chance that the rating is not precise and this may be something that leads people to think certain ratings show huge visible flaws, an SI1 I color GIA certified stone can be absolutely beautiful but if someone is selling a non certified I2 K color saying it's an SI2 H of course one may think anything less than VVS F is not worth considering.........