The above and below photos were taken with my LG G4. To manage a 30 second shutter time at ISO 50, I used a ND filter which I had adjusted in strength. Without the filter only 8 seconds would be possible without making the shot too bright.

I just need to establish a secure method of attaching the ND filter to the G4. For information the G4 was up against double glazed windows. The ND filter was one used for a DSLR and was a variable ND filter.

If you tap on photo to enlarge you will see the light trails more clearly.