Controling exposure with the ND filters
 

This might sound like a strange idea but I am interested to hear what more experienced videographers have to say about it:

I got the Z7 for wildlife as I needed a camera with the interchangeable lens option.
I currently work with the Nikon 80-200 f2.8 mounted with an adapter and it looks good -no problems in controlling the exposure as there is a aperture ring on this lens.
I need some more reach and I would love to use the new Nikon 200-400 f4 which is a phenomenal zoom.
The problem is there is no aperture ring on the Nikon zoom so the lens should be wide open as this is its default position. Since I would like to get a shallow DOF I shoot wide open 1/50, 25p, 0 gain. I think I can control the exposure quite well using the 3 built in ND filters plus one that is going to be added in the matte box or even on the lens itself.

Please someone let me know whether this can really work - this lens is pretty expensive - nearly 5 grand and I would hate to get it just to realise that I somehow got it wrong....

Thanks!

Ofer Levy - nature photographer
http://www.oferlevyphotography.com

Thanks for your email Alex. I realise it can not be done as each of the built in ND filters reduces the light by 2 f stops so controlling exposure this way is not practical....

Filters
 

Film cameramen have used this method for many years to achieve a universal f stop for the productions they work on and achieve a consistent "look " for the movie. The only snag is that every filter adds a layer of glass between image and sensor so you do lose a bit of quality.