When you hear the term “long exposure”, you most likely think about a slow shutter speed. This is too slow for sharp images and handholding. It might be something like 1/4 “, or maybe as long as 30″, which is the most common slowest shutter speed in DSLR and mirrorless cameras. However, shutter speeds slower than 30” can be advantageous in many long-exposure scenarios.
Bulb mode allows you to keep your camera’s shutter open as long as you hold the shutter button (with some limitations and tricks). This guide will help you understand the bulb mode on your camera and how to use it for long-exposure photography.
The Origins of the Word “Bulb”
Today, bulb mode most commonly refers to the camera mode or shutter speed setting that allows you to keep the camera’s shutter open as long as the shutter button is pressed, but the term “bulb” comes from the shutter release system that was used on early cameras. Long before digital cameras, view cameras and folding cameras generally used a rubber bulb as a detachable shutter release.
When a photographer put the rubber bulb into bulb mode, it would open the shutter. The shutter will close when the bulb is released and allowed to inflate. By pressing down on the bulb, photographers can have their shutter open for indefinite exposures.
The Basics of Bulb Mode and Where To Find It
On some cameras, bulb mode is accessed by turning to a separate mode on the mode dial. If your camera has a dedicated bulb mode, it will usually be abbreviated as “B.”
Otherwise, cameras will usually have a bulb shutter speed that is one increment lower than their slowest timed shutter speed. Manual (M) mode can access this setting. Simply set your camera to Manual mode and adjust the Shutter Speed to the slowest possible value, and BULB and/or B should appear.
Keep in mind, some cameras don’t have bulb mode. If you are having trouble finding it on your camera, read your manual, or search the internet.
Other than the mode itself, the only other thing you’ll absolutely need to use bulb mode is a sturdy tripod. Long exposures are very prone to camera shake, and even the slightest camera movements will produce a blurry image.
Tip: In theory, exposure time is only physically limited by battery life in bulb mode on a digital camera, and it can be extended using a vertical grip or other multi-battery solutions.
How to Use Bulb Mode In Photography
Now that you have found it on your camera, it is time to figure out how to use it. This requires some knowledge of the camera settings but bulb mode can be a wonderful way to start.
Unpredictable Subjects at Night
Bulb mode is particularly useful when you are shooting long-exposure images of subjects that have a varying duration or unpredictable occurrences.
Fireworks are unpredictable and difficult to forecast. You don’t want too many images. If the average firework lasts 10 seconds (this is just an example – a good baseline depends on your situation), dial in your aperture and ISO using a 10-second exposure, and then switch to bulb mode. Press the shutter button to start your firework exposure. When the firework you are capturing is gone, release the shutter button. This will produce a long-exposure photograph that only contains the firework you want.
An important thing to remember is that a shorter shutter speed will allow less light to reach the sensor, so if you happen to image a firework that is only five seconds long and you originally set your aperture and ISO to expose for a 10-second firework, your image will be too dark. Although this can be corrected to a certain extent using post-processing you need to also remember that images may appear too dark or bright. You can correct these issues by changing the ISO and aperture.
Bulb mode can also be useful for capturing lightning strikes, as it is impossible to predict exactly when a strike will occur during a thunderstorm. The mode allows a photographer to take a photograph until lightning strikes occur in it.
Varying long-exposure photography using bulb mode is also useful when photographing light trails. For example, if you are photographing a road at night that doesn’t always have cars on it, it’s hard to know how long of an exposure you will need to photograph a car going down the road fully. With a bit of aperture and ISO testing using a ballpark shutter speed, you can be ready for when a car comes down the road.
The beauty of bulb mode, is that it allows you to control how long you expose the image. Post-processing is much more efficient than darkening an image.
Light painting is very similar to the other types of varying long-exposure photography mentioned above. It is the use of a flashlight, or other light source, to draw and write in dark scenes. As the name suggests, it allows photographers to make images that are essentially paintings created with light. Without bulb mode, photographers are limited to somewhere around 30 seconds to do all of their “painting,” which makes complex light paintings close to impossible to achieve in one exposure. However, bulb mode unlocks the world beyond the 30-second shutter speed and allows light painters to draw for minutes at a time.
Here is a gear tip: When you first access bulb mode, it will appear that you have to physically hold down the shutter for your desired exposure time. Without an assistant, light painting would be nearly impossible. This is why a remote shutter release or intervalometer can be very useful. Most remote shutter releases plug into a port on your camera and will have a “lock” that allows you to activate the shutter and then keep it activated until you manually deactivate it.
Intervalometers are similar to remote shutter releases, and usually have a “long” mode that allows you to specify how long you want the shutter to be open. You should also check to see if your camera has a “timed exposure” or “bulb timer” mode (this is sometimes accessible in the settings menu), which will allow you to set a custom exposure time in the camera itself, eliminating the need for an external device.
Astrophotography: Star Trails
This article will only scratch the surface of astrophotography, but bulb mode is frequently used in different types of astrophotography. In one application, star trail images are made using anywhere from 10 minutes to hours of exposure. The rotation of the earth causes stars to appear as streaks in the sky over long periods of time and adds a unique twist to landscapes.
Bulb mode allows you to expose for long amounts of time, and this is a great choice for star trail photography.
Note that while it’s possible to create great star trail images using extra-long exposures (i.e. 10 minutes or more), most photographers stack several long-exposure images together to get their final product. Long exposures can heat your camera sensor which causes thermal noise and high-temperature pixels. Both artifacts are difficult and painful to remove, and photographers generally try to avoid them as much as possible. For example, instead of making one 30-minute exposure, photographers might use bulb mode to make 30 consecutive minute-long exposures. This also gives the photographer more confidence (and less risk) in exposing the scene correctly.
Astrophotography: Stars with a Tracker
Just like star trails, this application of bulb mode has many layers. The lack of adequate light is one of the greatest problems in astrophotography. To put it simply, to create well-exposed photos of stars, astrophotographers need to raise their ISO. This produces grainy noise that makes images less desirable. One way around this issue involves bulb mode and using a longer exposure than what is typically accessible in a traditional mode.
For example, two minutes allows more light to reach the sensor and eliminates the need to use a high ISO. Star photography has its challenges. As mentioned, star trails can be created by the Earth’s rotation at sufficiently long exposures. To compensate for earth’s rotation and create spot stars using star trail photography (bulb mode), star tracking devices can be used to produce long exposures in bulb mode.
Note: As with star trail photography, thermal noise and hot pixels are still challenges that come with star photography using a tracker. This is not a good idea for star trail photography, as the images must be consecutive. However, astrophotographers will often take a break between shots to allow their sensors to cool off and reduce thermal noise.
Bulb During the Day: Neutral Density (ND) Filters
Bulb mode typically cannot be used during the day without an ND filter, which is a device that blocks light from hitting the sensor. Daytime is generally too bright for the type of long-exposure photography that is enabled by bulb mode, so filters are used to block excess light and allow for long exposures at all times of the day.
With a sufficient ND filter, photographers are able to achieve exposure times that last a few minutes in the middle part of the day. Because it gives off a smooth effect, this filter is frequently used to photograph moving water.
It’s also possible to use this technique to get rid of crowds of people because if they’re moving over a period of a few minutes, they won’t show up in the final image. Extra-long exposures can unlock many abstract possibilities.
Whether you’re looking to photograph something that is constantly varying in duration or capture five minutes of starlight in one photograph, bulb mode is a great way to better understand shutter speed and the principles of advanced photography.
With some extra gear, you can use bulb mode during the day for creating silky-smooth waters landscapes. However, it is also possible to use it with just your camera and tripod to make stunning star trails images.
There are many unique, fun and exciting opportunities that can be uncovered by using the bulb mode feature on your camera.
Image credits: Photographs, unless otherwise noted, by Justin Hein