Rick Berk
Rick Berk

Rick Berk has been working in photography for almost 20 years, having started by photographing pro sports. Rick is a Canon Technical Specialist for EOS Pro Products and is responsible for training and providing technical assistance to Canon staff as well as pro photographers on all EOS products.

Long Exposures: Capturing the Passage of Time

June 14, 2012

"The hyperfocal distance is the closest distance at which a lens can be focused while keeping objects at infinity acceptably sharp."

One of the great things about photography is the myriad ways of conveying a scene to the viewer. In the end, it always comes down to a press of the shutter. For most people, making a photo begins with capturing a moment in time – 1/250, 1/60, or even 1/1000 of a second. Shutter speeds such as this will stop most action and freeze that moment. However, at the extreme opposite end of the spectrum is capturing the passage of those moments, by using a long exposure.

Typically, when using a long exposure, the shutter is kept open for anywhere from one second, to several minutes. Exposures of this length can create magical images when done well. Now, it's common to use a long exposure as a landscape shooter, or photographing a night scene. Whether it be a city skyline all lit up against a night sky or a remote location illuminated only by the stars, your exposure times will venture into that range of about 15 to 30 seconds or longer.

When planned for, long exposures can create the illusion of movement within the frame. To show that movement, it helps to emphasize a still subject against the moving object. Usually you will find that clouds moving in the sky, water in the foreground, or other objects in motion such as cars at night on a road, or people continually walking past will create that movement that will give the scene some extra interest. When set against a still object, this movement can then give the illusion of an almost 3D effect, with the static subject popping out of the image.

Long exposures are also useful when shooting reflections on water, especially when that water is choppy such as a lake or a river. The longer the exposure, the smoother the water will appear, thus smoothing out the reflection as well. Long exposures can give water a glassy look, making even rough water appear calm.

Required Tools

There are a few items that are a "must-have" for this type of photography. While most DSLRs will automatically set exposures of up to 30 seconds, for longer exposures you will need a remote release, such as the RS-80N3, TC-80N3, or RS-60E3. Your camera will determine which of these you can use. The EOS 7D, 5D-series, and 1D/1Ds series can use either the RS-80N3 or the TC-80N3. For Rebel and 60D users, the RS-60E3 will be the cable release needed. The RC-6 wireless remote controller can also be used with select cameras.

You may be wondering what the difference is between the TC-80N3 and the RS-80N3. It's really quite simple: The RS-80N3 is basically a shutter button removed from the camera. For bulb exposures, you will need to hold down this button for as long as you want the shutter open, and you will need to keep track of your exposure time and release the button when that time is up. A sliding lock switch allows you to press the button once, slide the switch in-place, and it holds the button down for really long exposures in Bulb mode. The TC-80N3 is fully programmable and allows you to set a delay before shooting starts, as well as program in the length of the exposure, up to 99 hours. It also offers built-in intervalometer functionality.

Beyond the remote releases and timer controls, you will definitely need a tripod. During a long exposure, the camera must be absolutely still, as any shake will ruin the image. The primary consideration when choosing a tripod is that it must support the weight you will be putting on it – body and lens combined. It needs to be sturdy and stable so it won't shake, especially if there is a breeze. While compact and lightweight tripods may be easier to carry, they may not sufficiently support the camera and lens. If the tripod doesn't provide proper support and stability for the job, it's not worth carrying at all.

The next item that should be in your bag for this type of work is a neutral density filter, or perhaps several. Neutral Density (ND) filters reduce overall illumination without effecting color or contrast. They would typically be used when you wanted to shoot at a slower shutter speed or wider aperture than your ISO or light reading indicates. They range in densities from 0.3 (1 stop) to 4.0 (13.3 stops). A 0.3 ND filter will appear to be light grey in color, while a 3.0 filter will be almost black, and nearly impossible to see through. It's important to note that the filter factor is measured under midday lighting conditions, so depending on the light you are shooting with, your exposure difference with a 3.0 ND filter may be greater than the 10 stop filter factor at which it is rated.

In the past few years, variable neutral density filters (VND) have become increasingly popular, with several models now on the market. VND's are comprised of two opposing polarizing filters. The outer filter can be rotated over the non-rotating section to create densities that range from 2 to 8 stops. One variable neutral density filter can easily replace several ND filters, allowing you to work more quickly and spend less time changing filters.

One strategy often used by serious landscape shooters who may use various lenses, with different screw-in filter sizes: buy one filter for the largest-diameter lens you own, and use commercially-available step-up rings to fit it onto lenses that take smaller-diameter filters. Take some test shots first, however, if any of the smaller-diameter lenses are ultra wide-angles, to insure that with the step ring in place, you don't get any unexpected lens vignetting (darkening) in the corners of your images.

Finally, there are several things to keep on hand that may prove useful when making long exposures. First, a flashlight is always handy, especially at night. If you're photographing in an area with no streetlights or little ambient light, it will help you to set up and adjust your equipment. Moreover, if you have a foreground object that is not well lit, you can use the flashlight to "paint" the foreground object with light. Lighting gels can be helpful for this purpose as well, so the light can be customized to the scene.

A lightweight, black, opaque cloth will be handy for when you need to cover the lens during a long exposure. At times when photographing at night, a car's headlights or a jet streaking through the sky, can ruin an otherwise good exposure. With a black cloth, you can cover the lens to "pause" the exposure and continue when the offending object is out of your shot. You want to be sure the cloth is light enough that it does not shake the camera during exposure. A baseball cap will also work well, simply by hanging it on the lens.

You may also want to have a portable stool or chair handy. It gets tiring standing around waiting for long exposures!

Camera Settings
ISO

Your ISO setting will vary dependent on the scene, but generally you will need to set it higher than ISO 100. When using a 10 stop neutral density filter, in order to avoid exposures longer than a few minutes, you will find yourself setting an ISO anywhere from 100 to 800, depending on the lighting. The image of Divide Mountain, in Denali National Park, was taken at midday with an exposure of 70 seconds, ISO 100, at f/8. Meanwhile, the shot of Sunset at Otter Point was taken at an ISO 1000 at f/8 for two minutes.

Because extreme neutral density filters are so dark, it is very likely that your camera will be unable to give you a proper exposure with the filter on. In such cases, you will need to get your base exposure without the filter, using the camera's meter. Then you will have to do a little math and add in the filter factor. Keep in mind, as stated earlier, that the filter factor is not linear, and may be greater than what is stated on the filter due to different lighting conditions. For instance, for Sunset at Otter Point, the exposure WITHOUT the filter was 1/40 at f/11, ISO 100. That's a difference in exposure of 16.6 (ISO: +3.3, Shutter: +12.3, Aperture: +1) stops!

For night scenes, without a filter, finding exposure can be a bit easier. If your scene is lit by city lights or moonlight, the camera will most likely be able to set exposure up to 30 seconds. If you want a longer exposure, it's as simple as doing the math from 30 seconds to the desired exposure you want. For the shot of Half Dome Under The Stars, the exposure was set to ISO 800, f/1.4, for 15 seconds.

Shutter Speeds

This is where the fun starts. Depending on the effect you are looking for, a long shutter speed could be anywhere from one second to several minutes or more. A one second exposure will give you a slight blur of water, while longer exposures of several seconds to a minute or two will give you that creamy, silky look that makes water look dreamy or glassy, depending on the way the water is flowing.

If you want cloud movement, you'll have to take into account the speed at which the clouds are moving. If they are moving fast, an exposure of 30 seconds or so will get great movement, while slower-moving clouds may require a minute or two or more to really show movement.

If the night sky is something you're going after, things get a bit tougher. If you want star fields, with no trails, exposures should be no longer than 15 or 20 seconds. A good starting point will be 15 seconds, f/1.4, at ISO 800. The EF 24mm f/1.4L II lens is excellent for these kinds of scenes. Stars' visibility will depend on a number of environmental factors, including light pollution, elevation, and the presence and phase of the moon.

Aperture

Your aperture will almost always be chosen based on the depth of field you want in your image. For most landscape shots, somewhere between f/8 and f/16 will be fine. However, with a 10 stop ND filter, f/16 will likely provide an exposure of over 7 minutes, so unless you want to raise your ISO, f/11 or f/8 will be the best choice.

When shooting the night sky, without getting star trails, an aperture of f/1.4 will be necessary. Many may shy away from this, feeling the depth of field will be too shallow. However, when shooting a really distant subject such as Half Dome Under The Stars, you need to focus ON A STAR. Simply turning the lens to infinity will NOT work – most modern lenses are intentionally designed to focus beyond infinity.

The best way to focus on a star is to find the brightest one in the sky, turn on Live View and zoom in to 10x magnification. Then manually focus on the star until it is sharp. Turn off AF so the lens does not refocus, and recompose your image in the viewfinder. Then simply take your photo. The image will be sharp, as long as when you compose, you pay attention to the hyperfocal distance.

The hyperfocal distance is the closest distance at which a lens can be focused while keeping objects at infinity acceptably sharp. When the lens is focused at this distance, all objects at distances from roughly half of the hyperfocal distance out to infinity will be acceptably sharp. So by focusing on a star, you ensure foreground and background sharpness, even at f/1.4. For instance, at 24mm, f/1.4, for a subject 200 feet away, the hyperfocal distance is 45 feet. Everything beyond 22.5 feet will be acceptably sharp, giving you a deep depth of field to work with. There are countless hyperfocal distance calculators available online, as well as smartphone apps available to help you calculate the hyperfocal distance.

Mirror Lock-up: When and Why?

Under most circumstances having your camera on a tripod will allow you to take good sharp photos. However, with shutter speeds between 1/2 second and 1/60 of a second, the vibration of the mirror as it lifts out of the way of the shutter can sometimes cause a slight blur in your photos. When using shutter speeds much longer than that, the vibration is not happening long enough during the exposure to have much of an impact.

Live View behaves much the same as mirror lock-up, with the added bonus that you get to see your composition on the screen before taking the photo. However, if you are using a strong neutral density filter in the range of about ten stops, Live View will not be able to display an image due to the density of the filter, so in this case, it's best to avoid Live View. It's also important to note that using Live View raises the camera's temperature when used for long periods. If you plan to make long exposures, it's best to shut Live View off before releasing the shutter and let the camera cool down for a few minutes, as the raised temperature could degrade image quality.

Noise Reduction Settings

For long exposures, especially when delving into the range of shutter speeds from 30 seconds to several minutes, digital noise is going to be a factor. Fortunately, Long Exposure Noise Reduction is a feature on all current Canon DSLRs, and it does a fantastic job of cleaning up noise from long exposures.

Long Exposure Noise Reduction can be set to Enable, Disable, or Auto. In the Auto mode, the camera will determine whether or not it's necessary for exposures of one second or longer. When set to Enable, the camera automatically applies Long Exposure Noise Reduction to all exposures longer than 1 second. (Please note that at shutter speeds faster than 1 second, Long Exposure Noise Reduction is ignored, and has no effect – thus, it can be left "enabled" all the time if you like, and it only is applied in actual long-exposure situations.)

Long Exposure Noise Reduction works quite a bit differently than High ISO Noise Reduction, as there really is no loss of detail. There is one sacrifice however: your camera will be unable to make another exposure until the Long Exposure Noise Reduction has finished. The time that takes is exactly as long as the exposure it was reducing the noise for. So, if you make a 30 second exposure, Long Exposure Noise Reduction will take another 30 seconds of processing time, during which time you will be unable to take another photo with your camera.

What's happening is this: your camera makes its exposure for the image. Long Exposure Noise Reduction then kicks in, and charges the camera's imaging sensor for the same amount of time, making a "dark frame." The camera then compares the noise in the dark frame with the noise generated in the image, and removes any noise that is the same. This method is known as dark frame subtraction.

High ISO Noise Reduction is quite different, and tends to be much more subjective and open to user preference. As there will be times – at night or when using high-density filters – that you will be raising your ISO and you will want this feature enabled. For a more in depth explanation of High ISO Noise Reduction, read this article.

Battery & Power Considerations

Digital SLRs require some battery power in order to keep the shutter open during long exposures. So while you may be able to take hundreds of pictures on a single battery charge in ordinary daylight situations, you'll find batteries get used-up a lot quicker when you take a series of long exposures.

At normal temperatures, here's a rough idea of how long a fully-charged Canon-brand battery can operate when you're in Bulb mode (total shutter open time, whether for one single long exposure, or many shorter ones):

  • EOS Rebel series: approx. 2~2.5 total hours
  • EOS 60D: approx. 6 hours
  • EOS 7D: approx. 2.5 hours
  • EOS 5D Mark III: approx. 4 hours
  • EOS-1D X: approx. 3 hours 45 minutes

Keep in mind these figures don't account for extensive use of Live View, or cold ambient temperatures. Spare batteries should be kept on hand. You will also want to make sure that you have enough charge left in the battery for the camera to both make the exposure, AND perform the long exposure noise reduction, if needed. The appropriate accessory Battery Grip for your camera can be handy here, as it can double the shooting time because it houses two batteries.

If possible, it may be desirable to use the appropriate AC adapter for your camera, so that there is no risk of a camera shutdown from loss of battery power during a series of long exposures.

Setting the TC-80N3

The TC-80N3 time controller can be invaluable when shooting long exposures. To set it, simply follow these three steps:

  1. Press the Mode button to select the LONG exposure mode
  2. Press inward on the jog-dial until seconds, minutes or hours is blinking; and dial-in the values you want to set
  3. Press the Start/Stop button to begin the exposure and you're done!

If you are using Mirror Lock-up, you would simply press the shutter button on the controller, then press Start/Stop.

Final Notes

Long exposures can change the way you look at a scene and add a new dimension to your images. It's important to keep in mind a few basic tips. First, look for objects in motion against still objects, like water against rocks, or moving clouds in the sky behind a strong foreground object such as buildings or a mountain. Second, note that when adjusting your exposure, 1 stop can be as much as several minutes, so changing the ISO or the aperture may be more appealing than adding two more minutes to the exposure time. Finally, don't be afraid to experiment. In the digital age, it's easy to try new things and immediately see what works, what doesn't, and why. So go try a few long exposures and have some fun!

The CDLC contributors are compensated spokespersons and actual users of the Canon products that they promote.

All images are copyright Rick Berk

http://learn.usa.canon.com

© 2017 Canon U.S.A., Inc. All Rights Reserved. Reproduction in whole or in part without permission is prohibited.