There seems to be an increasing number of so-called "true parabolic" umbrellas and reflectors being marketed lately. Being a skeptical old so-and-so, I'm yet to be convinced of any practical advantage. Also, some basic optical theory would seem to contradict the maker's claims.<p>Firstly, a parabolic reflector should follow a perfect parabola to be called "true" and thus have a single point of focus, which a foldable umbrella or strutted reflector obviously cannot do.<br>Secondly, the silvering of umbrella fabrics isn't anywhere near perfectly polished, and so can't reflect perfectly.<br>Thirdly, these umbrellas are used with flashheads that aren't a true point source.<br>Fourthly, it would be quite tedious to have to set the flash head at the exact focus of the parabola - assuming it actually had one.<br>Fifthly, the flash would have to radiate light evenly over nearly 180 degrees to fill the parabola.<br>Sixthly, these things are often used with a diffuser over them or as shoot-throughs.<p>This last point is the one I have a real issue with. A good diffuser is supposed to completely break up any directionality of light and scatter it over a wide angle; so what's the point of carefully shaping a light beam in a parabolic reflector and then diffusing it? That's like carefully arranging a train of dominoes, and then randomly kicking them all sideways.<p>Anyway, the question is, can anyone whose used or seen the results from a "parabolic" brolly really see any difference between it and an equivalent sized, but with no claim to being parabolic, ordinary brolly?<p>P.S. Has anyone ever seen a wraparound softbox anywhere? That is, one with a concave front.