A fixed ND filter blocks a single f-stop of light exposure, whereas a variable ND filter blocks a range of light exposures.
A Variable ND filter can be rotated to adjust the amount of light being blocked from your camera sensor, whereas a Fixed ND filter blocks out a fixed amount of light. For example, our Variable ND2-400 filter blocks out 1 f-stop – 8 f-stops), and our ND64 blocks 6 f-stops. A Variable ND filter offers more flexibility and is a good option for adventures with unpredictable light conditions. But it’s worth noting Variable NDs have limited applications with wide-angle and telephoto lenses. Read more on that here.