Camera in hand, you’ve journeyed to that coveted destination that begs to be photographed, only to find that so has everyone else! You cannot come back later when it has quieted down, so how do you go about capturing an image that is free of passers by? If it is a place where people move in and out of the scene over time, you can remove them by shooting long exposure shots using neutral-density (ND) filters.
Neutral-density filters are grey, which allows them to absorb the light that enters the camera without changing the colour. This lets you take long-exposure shots that require shooting at slower shutter speeds than normal.
When the shutter speed is longer, moving objects become blurry or invisible. This is because moving objects move out of the scene before the light reflected off them is enough to form an image.
Choosing the right ND filter depends on:
- How fast people move through your shot
In areas where people move throughout the scene, you’ll typically need to slow down your shutter speed to 30 seconds or even up to 5 minutes. This requires using a dense filter, e.g. a 10-stop ND filter.
- The time of day (available light)
Neutral density filters range in level of transparency; measured in “stops” of light. The darker the filter, the more light it will absorb, allowing even longer shutter speeds. During bright daylight, you’ll need a high-density filter (e.g. ND 16) that lets you slow the shutter speed down to a few minutes. During dusk or dawn when the light is less intense, you can get away using a less dense ND filter, e.g. ND 4.