One of my absolute favorite things to do with flowing water is long exposure photography. I would be willing to bet at least a few of you have taken photos of water and the photo simply froze the water in place. You’ve looked in envy at the photos others post that show water in silky smooth motion, as in the photo above. If you have ever wondered how to get that silky smooth look of water when you take photos, then you’ll want to read on to find out how it’s done.
What Is Long Exposure Photography?
Long exposure photography is common in astrophotography. Long exposures help to gather as much light on the digital sensor in your camera as possible. In fact, in astrophotography, we normally shoot a series of tens to hundreds of long exposures and then using software we stack and align the images to bring out even more details from a deep space object.
I’m sure at this point, you are asking yourself, what does that have to do with shooting photographs of running water? Well, it has everything to do with it. Other than the need to stack photos, we use the same techniques as we use in astrophotography. The difference is in one of the tools we use to make these photographs possible.
Tools For Long Exposure Photography
Now let’s look at a few of the tools you will need to shoot long exposure photography in the daytime.
First, you will need a DSLR camera so you can control focus and exposure time. You need a detachable lens that has threads in the front to allow you to attach filters to your lens. The DSLR camera also should have a bulb mode so that you can control the time of your exposure.
The second tool you will need is a 1000x Neutral Density Filter. This tool is imperative to do this type of photography. This filter cuts down ten stops of light entering the lens of your camera and hitting the sensor. Without this filter, daylight long exposure photography would be impossible. There would be so much light hitting your camera’s sensor, the image would be simply blown out and completely white.
The third tool you will need is called an intervalometer. This allows you to control the amount of time your camera shutter is open and collecting light. This tool also allows you to release the shutter of your camera without touching it. This is important because just the act of you pressing the shutter can cause enough vibration to ruin your shot.
The last tool you will need is a sturdy tripod. Make sure to get the best tripod you can afford. If you purchase a cheap flimsy aluminum tripod, you will be disappointed with the results. As noted, any vibration can ruin your shot. Cheap tripods won’t resist wind and other vibrations, which will ruin all your hard work. Another consideration for tripods is weight. Carbon fiber tripods may be a little more expensive, but they weigh less than a comparable aluminum tripod. Less weight is an important consideration when you are hiking and carrying all your equipment on your back.
Settings For Flowing Water Shots
The first consideration is the aperture setting. A wide aperture (low f-stop) lets in a lot of light and causes a narrow depth of field. If you want to learn more about depth of field, you can read this article. Since we are already decreasing the amount of light reaching our camera sensor, we don’t want to let in even more light, so we should use a higher f-stop number. This in effect does two things: decreases the amount of light hitting the camera sensor and increases the depth of field so that more of our scene is in focus.
For ISO settings, you want to use a low ISO setting. Remember, increasing the ISO setting increases the sensitivity of your camera sensor. So using a 100 or 200 ISO setting will help us control the brightness of the photo in another way.
The shutter speed is the final setting in the exposure triangle. Shutter speeds are set on the intervalometer for this type of shooting. I use anywhere from 15-30 seconds for most shots. My go-to setting for long exposure photography is 20 seconds. Then I’ll adjust the settings after taking a test shot.
Getting The Long Exposure Shot
My workflow for setting up these shots looks something like this:
First, I will survey the area to decide my angle to shoot from and framing. Then I attach the camera to the tripod and attach the intervalometer. Next, I set the intervalometer to 20 seconds then set the initial camera settings as above or according to lighting conditions.
Cascading Falls Next To King’s Falls
Once I have the camera set up, I frame and focus. Notice I do this before attaching the ND filter. Once you attach the ND filter, you will not be able to see any details in the scene well enough to focus. So be sure and frame and focus prior to attaching the ND filter. Also, be sure you don’t bump the focus as you attach the ND filter. It is easy to do on some lenses.
Once everything is set up, open the shutter using the intervalometer. The shutter will stay open for 20 seconds, or whatever you have set on your intervalometer. Once the shutter closes, you can review the image on your LCD screen and make adjustments as necessary.
How Does It Work?
When you do long exposure photography, the image builds up on the sensor over the amount of time determined by your intervalometer. So instead of freezing the water in an instant, the image of the water builds up over the set time. This is what creates a smooth look to the water.
You want to do this on a calm day if you have plants or other objects that can move in the background. Wind will cause plants and trees to sway, which will make them blurry in the final image. You will notice that all the trees in the background are sharp in the images in the article because it was relatively windless on the day I took them.