Make Your Photos Show Time in Motion with Neutral Density Filters
The very word "snapshot" invokes the idea of capturing an instant in time. Showing the effect of motion in time, however, requires a neutral density filter to keep your photography from overexposure. Heres some information on these filters and how they are used.What subjects can you photograph with a neutral density filter?
- Waterfall: Create a smooth flowing effect that matches what the human eye perceives.
- Birds: Allow the wings to blur, indicating how fast they are moving.
- Traffic: Make headlights and tail lights appear as white and red snakes tracing commuter routes across the roads.
- Sports: Show which players are active at the moment.
Use this type of filter to include details from light and dark regions in the same shot, such as when you want to take a picture of a sunset. To see why, consider how you would achieve that sunset with regular filters. When you adjust the camera for the brightness of the sky, the landscape appears too dark. When you adjust the camera for the relative dimness of the landscape, the sky is overexposed, and the colors of the sunset are washed out.
Next time, you fit the graduated filter over the lens. The filter is grey on one side and clear on the other. You adjust the filter so that the grey side overlaps the sky and the clear side is aligned with the landscape. When you take your photo, the light from the sky is filtered so that it doesnt overexpose. Now, your photo shows details of both land and sky with the optimal amount of exposure.Can you get graduated effects with regular ND filters?
Yes, if youre willing to use photomanipulation software to achieve your results. With a set of ND filters that each have different stop values, you can take that photo of a sunset without the need of a variable filter. Mount the camera on a tripod or some other stable base, then use a filter with a low stop value to photograph the landscape and a filter with a high stop value to photograph the sunset. With your computer and digital software, you can stitch the lower part of the landscape photo with the upper part of the sky photo to create a photo that highlights both land and sky.Why would you use a variable filter?
It can save on weight and clutter for when youre on a hiking trip with your camera, and you dont want to be loaded down with a bag full of filters. Variable ND filters are convenient because they can be dialed to different stop levels so that you need to carry only the one filter in your camera bag instead of a complete set.
Be aware, however, that at higher stop levels, using a variable filter can create vignetting or a darkened X effect on your image. As a contingency for when you expect to take bright exposures, such as of the daytime sky, you may want to equip yourself with fixed filters at higher stop levels to use in addition to a variable filter.