Several months back I was asked to do an article about long exposures using Tiffen ND (neutral density) filters, more specifically, the Tiffen Apex ND filter from their XLE Filter series. The Apex is a 10 stop ND filter. It is also equipped with a standard near IR blocker and a hot mirror to eliminate all IR pollution that you might normally get with long exposures.
This image was made at a lake close to my home. It was taken near mid day, but using the filter I was able to get the exposure over a minute. Which allowed me to show some movement in the clouds and water, leaving it looking much smoother than it was.
Hover over the image to see camera settings. Click the image to view it larger.
If you aren't familiar with using Solid ND Filters there are a few things to keep in mind. You will need to compose and focus before attaching your filter. Most likely you won't even be able to see through the camera after attaching the filter. Be sure to switch your lens to manual focus. If not, your camera will try to auto focus, which it will never be able to do, with the filter attached. Another good tool to have is a ND Filter Calculator app to keep on your smartphone. There are several of them that you can download for free and they all do the same thing. You can put in your base exposure (aperture, ISO and shutter speed) and the number of stops of your ND filter and it does the math to calculate your new shutter speed. It's super simple. Even I can use it!
This image was made using my Sony A7R II, Tamron 24-70mm Lens and Tiffen Apex ND Filter. Of course, a minute long exposure requires a very stable tripod. For this shot I used my Sirui T-2205X and G-20X Ballhead. Although this is designed to be more of a "travel" setup, it is more than sturdy enough to hold your wide angle lens for long exposure photography.