What i did here was using an 8 stop ND filter, a 22 F stop and a long shutter time, about 8 seconds I guess. What you can do now is capture motion, or when the shutter time is long enough, vanish people out of a scene. Interesting moving objects are clouds, cars, people, trains, water.. Yes you should use a tripod, but it’s not necessary, depends on how creative you are!
See the results below! Those guys from Digital rev, inspired me and check out this video how they use nd filter! They got a lot of nice tutorials on their youtube channel so make sure to check them out and expand your creativity.