Using two polarizers on a mattebox as variable nd

I'm trying to use two polarizers. One linear and the other circular. I plan to put the circular in the rotating filter tray on the matte box (4x4). The idea is to combine two of them to create a variable ND. I'm hoping there won't be vignetting.

Has anyone tried this setup? are there any adverse effects of doing this or would this be pretty much like using a mount-onto-lenses (screw) filter? Are there any specific filters that you recommend to achieve this? Thanks

Why not use a circular variable ND at that point?

Why not use a circular variable ND at that point?

Sounds interesting, is there such a thing as 4x4 circular variable ND? I could certainly get one that screws onto the lens but then I wouldn't be able to use it with the mattebox which I find myself using a lot with the eyebrow.

In my experience, matte boxes don't use variable NDs, but use different grades of ND and replace them as needed. I think combining polarizers could cause some very strange image patterning, but I could be wrong about that.

Hey guys. I've deciced to go for a regular ND filter (not variable) to use with my 4x4 mattebox. I'll probably start with 1 or 2.

Which filter or pair of filters would you guys recommend for typical sunny shots? I was thinking the Tiffen 4 x 4" Neutral Density 0.6 Filter for a 2 stop exposure reduction or should I try something different?

BTW, this is for a BMMCC.

Thanks

Depends on the lens, but you are going to need at least a 1.2 or 1.8 for sunny day shooting, to keep,yiur f/stop below f/8. I started out with a 0.9, on the Pocket Camera, and it was not enough.
Cheers

Take a look at the SLR Magic Image Enhancer Pro with 4 stops ND filtration (that’s one filter doing the work of two separate filters)!


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