Need help choosing a Neutral Density Filter
I would advise against a slide in filter for such a high stop number. An ND 10 is super dark. So any stray light is going to affect your exposure. Im a massive fan of slide in filters for ND grad's because of their flexibility. When I want dark, I use screw in filters. My go to kit in harsh midday sun is a B+W ND 1000x and a Hoya pro 1 CP screwed together. At ISO 200 F16 they are giving me an exposure of around the 60 seconds mark..