Introduction to Long Exposure Photography

December 14, 2013  •  Leave a Comment

Introduction

First things first, what exactly is long exposure photography? Think for a minute what happens when you find yourself standing in front of an interesting subject, and press the shutter button. Your camera captures a scene that is essentially frozen in time. Nearly all motion is stopped and you are left with a picture representing an infinitely thin slice of existence. Now imagine that instead of capturing that single instant, we could leave the shutter open as long as we desired and capture a scene as it unfolded, over an extended period of time. Well that’s exactly where long exposure photography comes in to play.

sunrise at the Old Orchard Beach Pier in maine
Old Orchard Beach - An already colorful sunrise is enhanced by the motion provided through long exposure photography.

 
I was first drawn to this form of photography by browsing through the pages of various landscape photo magazines. I would see the obligatory black and white shots of clouds screaming over mountains at 1000 miles-per-hour or rocky jetties extending into a sea of fog and my first thought was always, “Man, that is cool. How did they do that?” Little did I know that I already possessed most of the equipment needed to capture my own long exposures, and all that I needed to learn was a little bit of the technique.

Chocorua Lake Sunrise
Chocorua Lake Sunrise - Some of my first experiments with long exposure photography were spent trying to emulate what I saw in the magazines.

The Gear

There’s a great chance that you already own most of the requisite gear to start capturing some time-bending shots of your own. Here are the absolute essentials followed by some accessories you may wish to have, in order to take your shots to the next level.
 
Camera - This is an obvious first item on the list, but you need to make sure your camera is capable of some level of manual manipulation. At the very least you need a way to control shutter speed. Most cameras allow manual adjustment of shutter speeds up to 30 seconds. If your camera has a “Bulb” mode (sometimes just, B) then this is even better. It means your shutter will stay open for as long as the button is pressed, essentially giving you full control over the shutter.
 
Tripod - A sturdy tripod is a must! Since your shutter will be open for seconds, or minutes at a time, any camera shake will lead to a blurry final image that no amount of sharpening in post-production can save. And remember, a heavy tripod does not necessarily mean it’s sturdy. Check for weak points such as pinned connections in the legs or head which can often work themselves loose after seeing action in the field. Usually a quick tightening will snug things up.

Optional Gear

Remote Shutter Release - If you don’t have one of these, you will be forced to physically hold down the shutter button during your exposure. A remote cable lets you do this, remotely. The big advantage is that this reduces unwanted camera movement which can lead to a blurred picture. It’s also useful when shooting in cold weather, as you can keep your hands in your pockets, and out of the elements. You can get fancy here and purchase a wham-o-dyne wireless remote trigger with all the bells and whistles, however the $4 Korean unit I found on Ebay has worked fine for over a year, been dumped in snow, dropped in salt water, and still keeps ticking.
 
Neutral Density Filters - Neutral density filters, or ND for short, are a quick way to cut down the amount of light reaching the camera’s sensor. I will begin by saying that it is possible to take long exposures without ND filters, but you will be very limited as far as time-of-day which you can shoot. This would include times when there is very low natural light, such as dawn, dusk, and night-time. Basically any time when the sun is below the horizon. An exception to this rule-of-thumb is if you are deep in the woods shooting a stream, exposures of up to a few seconds are sometimes possible without an ND, even during day-time. Of course this all depends on how much your lens can stop down the light on its own, with most able to close to f/22 or somewhere thereabouts.

autumn foliage at the Flume Covered Bridge
Flume Covered Bridge - This photo was taken without an ND filter, and you can see the softened stream effect caused by a small aperture.
 
Purchasing an ND filter will probably be the biggest single improvement you can make as far as opening up possibilities for long exposures. No longer are you limited by time of day, and the ideas for shooting become limitless. I will not get too in depth on the science behind ND filters, as that could serve as an entire article in itself. Just know that ND’s can be purchased in a variety of strengths, or “Stops” depending on the amount of light they let through. For really long exposures during daylight hours, you should look into getting at least a 9 or 10-stop ND. The good thing is you can stack filters to effectively combine their light reducing qualities. If you attached a 10-stop filter to a lens set at f/22, you would be getting roughly 32 stops of light reduction. And if you remember back to photography basics, with each f-stop reduction you are halving of the light intensity from the previous stop. As the light trickles in to the sensor, we can really start to stretch out our exposure times for some crazy results. As an alternative to ND filters, a circular-polarizer (CP) can be used to stop the light down 1 or 2 stops. This isn’t much, but can make the difference between getting that extra second or two of exposure time.
 
sabbaday falls on the kancamagus highway
Sabbaday Falls - This shot was taken with a polarizing filter which allowed the exposure to be extended by a few seconds.
 
Viewfinder Cover - Not sure how essential this is, but it could help improve your shots. The theory is that stray light can enter the camera through the viewfinder and even the light sensor element, compromising your beloved exposure. To combat this, find a means of covering these elements when you are taking your exposures. I haven’t found this to be an issue in low-light situations, but if you are doing a lot of day-time shooting where there may be stray light, it’s worth a try. No need to get fancy either, I just drape an old t-shirt over my rig when I’m ready to hit the shutter, other people use pieces of black tape, you get the idea.
 
Exposure Calculator - This is especially helpful when using an ND filter to get those super long shots. Once you place your filter on, your camera will see that it’s extremely dark, and meter for the longest exposure it can, typically 30 seconds. Firing off a shot at this point will likely result in a heavily underexposed image, so we need to find a way to calculate how long to hold the shutter open for a properly exposed shot.
 
Initially I would take a best guess, hold the shutter open and then adjust the exposure time depending on the results. This trial-and-error approach is fine most of the time, however if you are shooting a colorful sunset or sunrise, you may only have one chance to get it right before the colors fade away into oblivion. A great way to do this is by using an exposure calculator. There are some free apps available online, and also some good charts to get you on the right track. The idea is that you meter the scene without your filter, find an equivalent exposure time knowing your ND’s f-stop, and bam, you know exactly how long to hold the shutter open. Of course, it’s not an exact science, but it will get you in the ballpark.
 
The downside is that most of these calculators are based on standard f-stop and exposure increments, and as such, there can be huge gaps in predicted shutter times due to reduced fidelity at the extreme ends of the scale (where we will be taking most of our shots). For example, a chart for a 9-stop ND filter might go from 1-2-4-8 minutes, and we will undoubtedly be in need of some higher resolution. To remedy this, I created a cheat-sheet specific to my 9-stop ND. It has equivalent exposure times for a range of about 20-900 seconds, which covers most situations.

sunset on the portsmouth harbor waterfront
Portsmouth Waterfront - With light fading quickly, you may have only one chance to grab that amazing shot you have envisioned.
 
TIP: When shooting a sunset, you may want to add an additional 15-20 seconds to your exposure time. For example, if you calculated 240 seconds for a shot, you may have better luck shooting 260 seconds. The reason being is that over the course of those 4 minutes, the natural light is fading quickly, especially if the sun has already gone below the horizon. You should counteract this by extending your exposure just a bit. The reverse holds true for sunrise when you may want to reduce your exposure a tad from the calculated number.
 
Noise Reduction - You may find that as your exposure times get longer, more digital noise is introduced. This is just an unwanted by-product of long exposures. Many newer cameras have long exposure noise reduction built right in, but if yours doesn’t, there are many programs you can use to help cut down on the noise during post processing. If you camera is a bit older, you may also suffer from “hot pixels” which show up as little red dots all over the frame. These are easily removed during post-processing as well.
 

Technique

 
Okay now that we have all the gear we need, we’re ready to go take some award-winning shots. Well, what the heck do you shoot anyway? As the artist, it’s really up to you, but there are some general subjects which lend themselves well to this type of photography.
 
Landscapes - Landscapes are a natural fit. Clouds are perfect because they represent a highly textured object in motion. After some trial and error, you will find which cloud formations are best, and schedule your shooting around them. What you are really looking for are low to medium level puffy clouds moving at a reasonable clip. Clouds that are too high will not move much (relatively) over the course of a minute or so, and the effect will be diminished. Shutter speeds of 30-60 seconds are usually enough to get some really nice streaking effect in the clouds. Low hanging storm clouds can create a cool dark and brooding effect, and are great for Black and White photography experimentation. As an advanced technique, try to place your main subject such that the cloud streaks act as leading lines, drawing the viewer in. Clouds that originate from a fixed point and spread radially outward tend to be more interesting (although not always) than clouds that just go from right to left across a frame. Experimentation is key here.

New Memorial Bridge in portsmouth nh
Memorial Bridge - Some low level clouds help add drama to an already great coastal scene illuminated by the setting sun.

 
Waterfalls - Waterfalls are another popular subject as long exposures tend to soften the water up a bit, making the composition a little less “busy”. Unlike clouds, you only need a few seconds to really soften up moving water, which makes it great to shoot if you do not yet have an ND filter, or just own a CP filter. Shooting moving water at 60 seconds or longer gives almost a hazy and dreamlike effect, and the original shape of the water starts to become a blurred mass. A lot of artistic license can be applied here for different effects.

autumn foliage at garwin falls in wilton
Garwin Falls - Shooting a waterfall during the autumn months can be fun with added effects from swirling leaves.

Seascapes - Seascapes are the next logical progression, and they combine the cloud movements and waterfall shots you’ve been perfecting. Seascape photography is an art in itself, but long exposure techniques can be used to separate your seascapes from the rest. Consider the same rules that apply to waterfalls here. Exposures up to a few seconds can create nice streaks and lines in the water, while exposures of a few minutes will smear the ocean into a white foggy haze. It’s all about taste, and what you are trying to evoke as far as emotion. Seascapes also can blur the lines between ocean and sky, and you can use this to your advantage in your compositions. Long exposures on the coast can reveal colors not seen with the naked eye, even long after the sun has set. Certainly a lot to master, but that’s the fun part!

 

fort foster pier in kittery maine
Fort Foster Pier - Piers and jetties are great seascape subjects to experiment with.
 
Car Trails - While nature provides its own forms of movement, man has spent the last few centuries perfecting his own. A prime example is the automobile. “Car trails” as they are often called are easy created by leaving the shutter open as cars pass by. The yellow headlights and red taillights are recorded as streaks, flowing across the frame. Exposures of 15-20 seconds can capture quite a bit of movement, granted the roads you are shooting are fairly busy. Because the effect is multiplied by the volume of cars, a popular place to shoot is off highway overpasses, or congested bridges. And since most of these shots are captured at night, you can also practice these techniques without an ND filter. Just be careful when shooting around roadways at night and keep your head on a swivel.
 

Advanced Techniques and Ideas

Ghosting Objects - Try taking a long exposure of a bridge or marketplace during the day (you will need an ND filter for this). You will find the cars and people can create a ghosting effect, and may even disappear completely if the exposure is long enough! Think of the classic “Grand Central Station” picture.
 
Star Trails - Another form of landscape photography that creates huge arcing trails in the night sky. Advanced techniques have you blend a series of 30 second exposures for best results, and minimize noise. There are free programs online that can help you do this.
 
Steel-Wool Photography - I will lump this together with light-painting. Light up a piece of steel wool in the dark, and spin it around to make sparks shoot everywhere. Do the same with LED lights to get eerie trails all over the frame.
 
Construction Zones - Welding and other hot work can shoot off sparks that when exposed for long enough can look like streaming yellow waterfalls.
 
Carnivals - Spinning carnival rides and Ferris wheels are great subjects to experiment with.
 
Fireworks - Bring your camera along with you next Fourth of July and see what you can capture. You can get multiple bursts in a single shot by placing your hand or lens cap over your lens in between the explosions.

Conclusion


That concludes my introduction to long exposure photography. My hope is to provide enough information so that someone with minimal experience can go out and start trying some new techniques. Once you master the basics, the possibilities are endless. Always remember to think “outside the box” and most of all have fun!  

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