I know this sounds out there...but has anyone ever taken a Dremel tool to a filter to etch a sort of diffraction pattern onto a cheap filter to see if it can work?
If not, I might have to find a sale on a bunch of el cheapo filters and see what effects can be induced...I would figure, like the grease/vaseline/greasy nose substances a center portion larger enough for the focus and meter to work would be needed.
I dunno it sounds like fun.
Heck I was even thinking there is this spray paint you can buy at WallyWorld and other stores, it's from Krylon I believe, but it adds a frosting to a window so you can add privacy but let light into the room. I have even used it on the glass panels I use under items I am shooting to not only eliminate potential "double reflections" when the frosted side is faced down, but also to have a matte finish surface rather than a highly polished surface under an item...but it can be applied lightly and maybe make your own "soft" filter if done just right. You could use a round sticker to cover the center while applying the treatment...
OK, so I am sitting here with waaaay too much time on my hands...my fridge died last night BUT my K20D is OFD so I am waiting for the brown truck, screw the two weeks of groceries I bought yesterday afternoon!!