Have a long phone call with Mr. Kean Millar today, and he just discovered the deep parabolic umbrella.
And this make me write such note.
I am not keen about those deep umbrellas although I do own a few and even with their expensive diffusion cap. The silver one create multi shadow that cannot complete fix with diffusion cap on and for taking the advantage of that similar parabolic shape you must pull the flash tube as deep as possible and this may result using just the center part of the umbrella it mean you may result a 80cm source when using a 105 deep umbrella ;)
I still using softbox aurora firefly par & tera-d for serious portrait works, and will just use those umbrella for
cheap clients casual works. ;)