| A lens which is corrected for spherical aberration is the type you want to avoid blurring at the edges. Chromatic aberration is more of a problem relating to spectrum shift, which is important for telescopes and the like, less so ( I presume) for pearls ( I have never used a loupe!) Perhaps it is more important for gems that exhibit fire and transparency? Don't know - my answers are based on astronomy, not gemology. My eyeglasses frequently showed chromatic aberration, wherein the full moon will have a yellow edge on one side and a purple edge on the other. |