In an earlier article, I wrote that neutral density filters are the secret weapon of the landscape photographer. I couldn’t work without mine and I suspect most landscape photographers would say the same.
But why are they so useful? There are two reasons. One is that neutral density filters give you control over exposure, and the other is that they give you creative control over shutter speed.
What is a neutral density filter?
First, some definitions. A neutral density filter is one that blocks light. The result is that less light passes through the lens and reaches the camera’s sensor (or film).
There are several ways of measuring the strength of neutral density filters, but they are basically all different ways of stating how many stops of light the filter blocks. Typical strengths are one stop (0.3 or ND2), two stops (0.6 or ND4), three stops (0.9 or ND8), six stops (1.8 or ND64 )and ten stops (3.0 or ND1024). Some manufacturers even make neutral density filters that block 16 stops or more light, although these are more of a specialty item.
This photo shows a ten stop neutral density filter mounted on a lens. As you can see the filter is nearly opaque and you can’t see through it well.