Got up to the Marin Headlands today to find the fog rolling thick through the Golden Gate Bridge.
Always looking for something different, I pulled out a few neutral density filters. Neutral density filters are like sunglasses for your lens. They come in various strengths allowing you to block as much as 16 stops of light or more if you stack them.
What I love about using long exposures to capture movement is that you never know what you’re going to get! The moving objects, in this case, the fog, paints the scene with movement or sometimes the objects just disappear! Note the lack of cars on the bridge. Even though hundreds of cars crossed the bridge during my 8 minute exposure, none of them showed! There were also a number of pedestrians on the bridge and sailboats below, but they’re magically gone!
To make your own long exposure magic, all you need is a very sturdy tripod, a cable release that allows you to keep the shutter open for the required amount of time, (Bulb setting on your camera) and a stop watch. You don’t even need a neutral density filter if you shoot at night however I encourage you to get a few ND filters and try shooting during the day. It gives you a much more interesting look.
What density filter you get is up to you, but the more dense the filter is, the longer you will be able to keep the shutter open allowing for a more magical image. I recommend getting a 10 stop ND and a 6 stop. You can combine both for 16 stops which is what I did for the image above.
A 10 stop ND filter is so dense that you cannot see through it, let alone focus through it so you need to compose your image and focus before attaching the filter. If your camera has a long exposure noise reduction setting, use it. It will give you a cleaner image however the drawback is that it will make another blank frame for as long as your shutter was open so you’ll need to be patient.
Determining exposure is easy! Before you attach your ND filter, take a meter reading at your chosen aperture and then simply reduce the shutter speed by whatever strength nd filter you want to use. In my case, I reduced the shutter speed by a factor of 16. If shooting with film, you’ll need to factor in reciprocity issues.
We carry a few different brands of ND filters at Camera West, including Heliopan, B+W, Hitech and Lee.
The photo above was shot at 12:30 in the afternoon with a 16 stop reduction, ISO 100, an aperture of f9 and shutter of 8 minutes.