One shot with the 18 stop Neutral Density Filter, Brixham Breakwater 

Great video Seb, it's amazing how the timer jumps up from 15 stop at nearly 3 mins to 20+ mins at 18 stop. This 3 stops make a massive difference. The science makes me smile too, how people can walk in and out of the photo but not enough light comes off them to be seen in the pic.

excellent job

Good work. When you start using filters over 10 stops the math gets funky depending on what you use to get the correct exposure. I did it manually and checked my work with the NiSi app and LEE ProGlass app. Correct exposure is 21m 20sec. Manual method and LEE app you get this. Using NiSi you get 21m 50sec. Like I said once you go beyond 10 stops it's really hard to get the correct exposure especially if you use calculators. Because camera math is not the same and people math.

Thanks for putting the app up it showed the settings COOL - tickety-boo shot by the way :)

Proper job mate looks great ..the black and white my favourite but both good ..hope you well

Brill Seb, that's one hell of a filter, oh yes awesome final result and just loved the black and white image. As with that amount of time did you get any hot spots in the RAW file?