A complete guide to using your camera’s bulb mode

Your camera’s bulb mode is a powerful tool that can be used to create particularly long exposures, but it requires a slightly different approach than when shooting conventionally. Here’s what you need to know to get great results.

What does Bulb Mode do?
First, what exactly does the bulb mode do and why would you need to use this? Every camera has a minimum and maximum shutter speed in its standard range. A typical DSLR, for example, will be able to capture images at shutter speeds as fast as 1/4000sec or 1/8000sec and as slow as 30 seconds or so.

What the bulb mode does is to increase the latter figure so that you can capture exposures of many minutes in length, typically 30 minutes but potentially as long as an hour.

Most scenes don’t require exposures longer than 30 seconds and so the normal shutter-priority or manual modes are appropriate here. Some scenes, however, may benefit from a far longer exposure.

The most common applications include capturing star trails, fireworks or lightning, or alternatively when light painting; while it’s perfectly possible to capture all four with exposures lasting less than 30 seconds, you can create more striking results by going longer.

Other uses for the bulb mode include capturing light trails from traffic or super-smooth shots of the sea in conjunction with a strong neutral density filter. You may also find the bulb mode necessary when your camera informs you that the limit of the standard shutter speed range isn’t long enough, such as when using particularly small apertures at night or in other darker conditions.

SEE MORE: Bulb Mode: how to get pro-quality shots in low light

Where to find Bulb Mode on your camera
The bulb option may be marked on a camera’s mode dial (usually marked ‘Bulb’ or simply ‘B’) or it may be accessed in the manual exposure mode by turning whichever dial adjusts shutter speed past the 30-second point.

This should bring up ‘Bulb’ (or ‘b’) on either the rear display or, if your camera has one, the top-plate display. This differs between models so check your camera’s manual if you’re not sure where to find this.

SEE MORE: Long exposure photography: how to set up your camera for perfect exposures

Preparation
Before you set up your shot, make sure your camera’s battery is fully charged, or at least not far off; bulb exposures can consume a fair bit of power and you don’t want your camera to run out of juice mid-exposure. Also, set your camera to the manual exposure mode for the time being rather than the bulb option – you’ll need this to meter the scene.

In many ways, the way to set up for a bulb exposure is similar to setting up for a standard long exposure. You need a tripod or some other kind of stable support that will ensure the camera doesn’t move at all throughout the duration of the exposure – otherwise, you risk introducing camera shake into your images, which will compromise sharpness.

For the same reason, you should use some method of triggering the exposure without you physically touching the camera at the time of exposure, such as remote release. Normally with long exposures you can get away without using one, as the exposure can be triggered with the camera’s self-timer function and it will end after a specific duration, without any further manual intervention.

With a bulb exposure things are slightly different. It may still be possible to start the exposure with the self-timer mode, which will allow you to trigger it in advance and avoid camera shake, although you still need to some way of ending the exposure. The reason for this is that most cameras won’t know when to stop, as you don’t dial in a shutter speed as you normally would.

If your camera has a bulb timer, however, you may be able to specify the duration of the exposure in advance, so check to see if your camera offers this.

If your camera doesn’t have a bulb timer option, the exposure can be performed in two ways (some cameras offer both of these). In the first method, the exposure will start when you press the shutter release button and will only end once you lift your finger, although this isn’t advisable as you would need to keep absolutely still for an extended period of time.

In the second way, you press the shutter-release button once to start the exposure and once again to end it, although by pressing it twice the potential for image blur through camera shake increases. Ideally you don’t want to press it at all, which is why a wired or wireless remote release is recommended.

If you’re using a wired remote release plug this into your camera, and if you’re using a wireless release make sure that it works by triggering a standard exposure.

If your camera has a mirror lock-up function, see if you can use this in conjunction with the bulb option, as this will swing the mirror out of the way prior to the exposure, which in turn will also minimise blur-inducing vibrations.

Also make sure to activate long-exposure noise reduction, as this should help to reduce the noise in your images, a significant amount of which can build up during a long exposure.

Once you’ve got your photo composition and focus right, switch to manual focus to prevent the camera from refocusing (assuming you’re using autofocus). Now, see if you can cover the eyepiece of your camera’s viewfinder in some way; there may be a blind next to the viewfinder or a small eyecup on your camera’s strap which fits into the eyepiece.

The reason for this is to prevent your camera’s metering system from being affected by any light entering the viewfinder, which can lead to inaccurate exposures.

Exposure
Now it’s time to decide your exposure. It’s likely that you already have an idea of what’s appropriate based on what your camera is telling you. If, for example, your camera states that the scene is one EV stop underexposed at 30 seconds, then a 60-second exposure should be about right.

If you’re using a neutral density filter that significantly lengthens your exposure, now is the time to fit it to the lens (and be sure to take its density into account when determining your exposure).

You can measure your exposure with a watch or the timer setting on your phone, or alternatively with an app that may even perform the necessary exposure calculations for you. You may find the latter useful, particularly if using a filter that significantly lengthens your exposure such as a 10-stop ND filter.

SEE MORE: How to always get exposure right – your camera’s exposure settings explained

Finally, turn your camera from manual exposure to the bulb setting and make sure your aperture stays the same, as some cameras may not maintain the same aperture as you change exposure modes. Trigger the exposure through your remote release and start the countdown.

Your remote release may have the option of locking the button by sliding a surrounding bracket, so use this if you don’t want to keep you finger on the button for the duration of the exposure. However you do it, just make sure you know how to end the exposure.

Once the image has been captured analyse your shot, zooming in to check key areas are in focus. It may be exactly how you imagined although it’s possible that exposure, focus or composition isn’t quite right. If this is the case, simply adjust your settings and retake the shot.

Final tip
It’s possible to damage your camera’s sensor by leaving it exposed to bright light sources for extended periods of time. You should be fine with stars, fireworks and lights from traffic, but be careful when capturing a strong light source that shines continuously.

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