16 stops to success
Take a test shot
Before you attach the filter, take a test shot to work out a normal exposure of the scene. Use whatever exposure settings you’re comfortable with – a good option is Aperture Priority with ISO100, aperture f/8. This is a good time to experiment with compositions and fine-tune your framing.
Lock the focus
The filter is almost opaque: once it is in place, you won’t be able to focus or compose. Get the focus correct now, then switch the lens to manual focus to prevent it from hunting. Fit the filter, making sure not to nudge the tripod out of place, and block the viewfinder to stop light leaks.
Set to Bulb
Most cameras max out at a 30-second shutter speed, so you need to set yours to Bulb mode if you want to go slower. This way, the camera stays open as long as the shutter is engaged. To avoid touching the camera, we need to use a cable or wireless release, or a phone paired wirelessly. This lets us tap to start and stop the exposure.
Using a 16-stopper
A 16-stop filter is suited to daylight conditions with bright skies. 16 stops is overkill for most situations, and we wouldn’t try using it in low light (unless you’re into four-hour exposure times). But if you like the long-exposure look or minimalist scenes, it’s a great addition to your kit bag.
Watch your timing
Now we sit back and wait, using a timer to watch the exposure length. Keep in mind that the conditions may change during the exposure, so you may need to judge things on the fly. Here the sun broke out from behind the clouds during a planned five-minute exposure, so we stopped it at 2 mins 16 secs.
Work out an exposure
An exposure calculator, like the Photopills app here, is very helpful for long exposures with ND filters. We input the settings for our non-filter test shot, set the number of stops, and let the app calculate the new shutter speed for us. Each stop doubles the time. Here, 1/200 sec becomes 5 mins 28 secs.