ND filters are some of the most commonly used photography accessories out there, and they are great for both creative and technical applications. If you have not used them before, this great video will show you how they work and what they are useful for.
Coming to you from Mike Smith, this awesome video will show you the ins and outs of ND filters and how they affect your images. Simply put, ND filters are just darkened glass that reduce the amount of light reaching the sensor or film. You can buy them at various strengths to cause correspondingly different reductions. The standard strengths are three stops, six stops, and ten stops, though you can go higher and lower as well. They have both creative and technical uses. For example, if you are shooting outside with a flash that does not have HSS and want to use a wide aperture, you may need one to bring your shutter speed back below the sync speed. They also have a range of creative uses. Most notably, landscape photographers frequently use them to smooth over moving water or clouds in the sky for creative effect. Check out the video above for the full rundown from Smith.