- Posts: 616
- Joined: Wed Jul 01, 2015 6:33 am
- Location: The Netherlands
One key consideration in switching from variable to fixed ND filters is your lenses. If you have standard DSLR or MFT lenses with fixed aperture stops, you're probably better off with variable ND since you can fine-tune your exposure by turning the ND wheel. If you're using cine lenses with aperture/iris rings then fixed ND is fine. My approach is to keep a fixed ND filter on my lenses (e.g. 3 or 4 stops) at all times and supplement it with a variable ND as needed.
On the original Pocket camera you needed to use ND filters for nearly all outdoor shooting to keep the aperture wider than approx. 5.6; once you stop down further than that the image starts softening due to diffraction. The new Pocket has a bigger sensor (full MFT size), and diffraction shouldn't start to become a risk until you go higher than about f11.
I guess the question of how many stops depends in part on what kind of conditions you envision shooting under and your goals in terms of depth of field -- if you're shooting portraits on bright sunny days at the beach, you may need 6-8 stops or possibly even higher. I was recently shooting at a beach in sun and had to use my variable ND filter on top of my fixed 6-stop filter to hit the lens's sweet spot.
I bet Denny Smith can chime in here with some of his wisdom on this topic.