I'm using a:
Full frame camera
20mm lens, 77mm diameter
9mm thick filter on end of lens (a tiffen variable neutral density filter).
My question is:
I'd like to be able to add a reverse neutral density filter to this set up without experiencing vignetting and keeping kit and cost minimal. I'm in the UK.
I would LIKE my solution to be a Singh-Ray P-series (84mm wide filter) held in a Cokin P wide-angle filter holder and a Cokin 77mm adaptor ring.
Does anyone know whether this will work or whether I will still get vignetting?
If it doesn't work, I'd have to upgrade to Singh-Ray Z-Pro filters which are bigger in size and £ so I'd rather not do it. Also in case anyone suggests, I don't want to hand-hold my filters since I do long exposures.
Many thanks in advance 
