BMPCC - Urgent help for Nd filter

For BMPCC is better a ND8 fixed filter or a variable ND filter?
ty for help

An IRND filter would be best.

I have 3 variable ND filters, from cheap to relatively expensive. At 200mm focal length, all of my filters will degrade the image quality, making the image blurry. Maybe the very expensive one will be better at tele focal length.

I now just use fixed ND filter and then use the aperture to further adjust the exposure. It seems good enough ... for me anyway.

As Adam stated. You need an IRND, if you already have a Variable ND then people have recommended Tiffen T1 IR filter as something people should get.