The rolling hills, forests, waterfalls, and prairies of southern Indiana defined the vision I see in nature today. In 1989, I moved to northern California and then again to my current home near Portland, OR, right in the heart of the beautiful Pacific Northwest.
Long-exposure photography has become very popular in the last few years. Many of our popular websites and magazines are featuring long-exposure photography. Several filter manufactures have also noticed this and have added neutral density filters to their offerings.
But what is a long exposure? Most DSLR cameras today will allow us to have a shutter speed set automatically up to 30 seconds. However to me a long exposure is just that, longer than I can render a subject in sharp focus. This could be anywhere from ½ second or a few hours, depending on the subject and effect I want to create.
Long exposures can be created in several ways. I can leave my shutter open long enough for a car or bicycle to drive by and create an interesting blurry effect.
Long exposure photography is also used in nighttime photography to capture stars patterns, or trails as well as even sharp stars set in the night’s sky. When my camera is on a sturdy tripod and the shutter is left open for a prescribed time, very vibrant and clear photographs can be made.
Long exposures can be used in light painting, when a scene is very dark. A light source is moved over the subject to add some light and ambiance. I often need to experiment with the amount of light applied to a subject so that I do not overdo the amount of light shining on the subject.
Finally the most often used application of long exposures for me is with moving water and clouds. The end result is often a mysterious, yet dreamy effect. Sometimes it’s even surreal. I can at times add a sense of movement by recording the moving clouds or water across the image. In essence this is a departure from normalcy both from an artistic sense, as well as a viewing experience. I am going to deal with making long exposures using clouds and water in landscape photography.
“First, I use a good quality digital SLR camera. Long exposures can introduce a bit of noise, so the better the camera’s sensors, the better my images will appear. I will not see this ‘noise’ or what are called “hot-pixels” on my LCD, but the problem will show up when viewing my images on the computer monitor. I also need a camera with a “bulb” setting which will allow me to keep the shutter open for as long as needed, allowing me to create some high-quality long exposures. I also use a remote or wireless shutter release that has a built-in timer that I can set for the proper length of time required for each individual image. Using such a shutter release is a lot more accurate than counting seconds or even trying to look at my watch in a dark area.
“I also use the same high quality tripod and tripod head I use for photographing in normal conditions. A tripod is necessary to produce sharp images. When making long exposures the tripod is even more important because my exposures can sometimes last several minutes. For maximum stability, I never extend the center column on my tripod.
Finally, I need my neutral density filters to slow down the shutter speed. What these filters do is block much of the light from entering the lens, which allows me to leave the shutter open for a longer length of time. Most solid ND filters are rated by the number of ‘f-stops’ of light blocked, with each added stop reducing the light by half, meaning the shutter must stay open twice as long for the exposure to be equal to no filter. This effect is exponential, for example a 3-stop ND filter reduces the light by 3 f-stops, so that’s 1/2 x 1/2 x 1/2 = 1/8 as much light entering the lens, requiring an exposure 8 times as long (2 x 2 x 2 = 8) for an equivalent exposure. A 3-stop filter is sometimes called an ND8 for this reason.
So, when using a 10-stop Mor-Slo ND filter, an equivalent exposure requires a shutter speed 1024 times longer than without the filter (2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 = 1024). This translates to less than 0.1% of the light getting through the filter to the lens. So for an equivalent exposure with the addition of a 10-stop ND, a 1/100 second exposure needs to be extended to 10 seconds, and a 1-second exposure needs to be 17 minutes!
Many filter manufactures make these neutral density filters and I have tried most of them. The two I use are the Singh-Ray 10-stop Mor-Slo filter and the Singh-Ray Vari-ND filter. Singh-Ray also produces a 5-stop Mor-Slo filter.
LONG EXPOSURE TECHNIQUE
Remember, we’re only discussing long exposures in landscape photography. Techniques for night photography, light painting and other artistic uses of long exposures require different methods.
Composing my image begins with choosing the subject and assessing the light. I begin by first making the same image without using the ND filter.
If this first image tells me I have chosen a good subject, with good light and one that has some moving water, clouds, or other moving action, I’ll proceed to create some long exposures.
After setting up my tripod and camera, I go through all the steps I do for normal photography. I then check the light and properly meter the subject without using any filters. Having a 10-stop ND filter on the lens while focusing will not allow me to see a thing. It is just too dark due to the density of the filters. Here is my procedure.
1) I compose, determine the aperture I want, and focus the image in the proper manner (Once I auto focus without the filter, I switch to manual focus mode).
2) I determine the shutter speed based in ISO and aperture without the filter on.
3) I carefully screw in my ND filter of choice, either the 10-stop Mor-Slo or the Vari-ND.
4) I double-check to make sure the screen that closes over my viewfinder is closed. This insures proper metering and prevents light from entering the camera while the shutter is open. It’s very important to prevent light from entering through the viewfinder.
5) I now set my shutter speed to the “bulb” setting allowing my shutter release cable or remote timer to control the shutter speed.
6) I determine how long I need my shutter to be open based on the shutter speed determined without the filter. This math can get quite complicated. I have developed a timetable, based on the math involved. NOTE: If your shutter speed is longer or shorter than desired, you can change the shutter speed simply by increasing or decreasing the ISO. Remember that digital noise increases with higher ISO’s as well as long exposures!
7) I set my remote cable release to the desired time based on the shutter speed with no filter attached.
8) Assuming my light conditions didn’t change, I make the image.
NOTE: There is a great free app that I use on my iPhone — its called LongTime Exposure Calculator and does just that. I find the free version of the app works great for me. For 99 cents, you can get the “Pro” version which includes a countdown timer for exposures over 30 second. There are a variety of similar free or low-cost apps available for iPhone and Android, so find one that works best for you.
There are a few variables that I try to consider when making long exposures.
1) When making long exposures, I will need to slow down even more than normal to make sure my settings are correct. Creating a concept for an image when making long exposures is very important.
2) After I make the image, I do not use my LCD to evaluate anything other than the histogram.
3) I like to change the ISO to make the shutter speed longer or shorter. When I get back to my monitor, I can choose the effect I prefer.
4) I always recommend shooting RAW files.
ONE LAST THOUGHT
This essay is not an advertisement. It is simply my endorsement. I have experimented with filters from other manufactures. I have found without question the Singh-Ray filters to be of the highest quality without any measurable color shift. Color shift is the biggest problem in filters, especially ND filters. There is no easy or cheap way to make a good quality ND filter. Singh-Ray filters are highly recommended.
I recently made two comparison images. One was using the Singh-Ray 10-stop Mor-Slo filter, the other with a 10-stop ND filter from Singh-Ray’s main competitor in a similar price range. The results speak for themselves. There is absolutely no color shift with the Singh-Ray, but a large shift with the competitor. These images were taken about 2-3 minutes apart. Same light, same camera settings 14 sec / f16 -1/3 comp ISO 200. Consider this when purchasing filters.