Using Bulb for Long Exposure Photography

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Thanks for reading! Andrew.



Rangitoto Island, New Zealand

The longest shutter speed available on an EOS camera is 30 seconds. But sometimes that’s not enough – there are times when you need a longer shutter speed. That’s where the Bulb setting comes in.

I took the photo above with a shutter speed of 201 seconds. The long exposure has blurred the water until it is smooth, almost textureless.

Muriwai, New ZealandMuriwai, New Zealand

If you use a shutter speed of 30 seconds, in most cases it isn’t long enough to achieve this effect. Compare the above two photos, both taken at the same location on different days. There is a big difference in the way the sea has been recorded, and it’s all down to the shutter speed used in each.

If you want the silky appearance of the second image, then unless the sea is still you need to use a shutter speed of a minute or longer to obtain this effect.

Bulb

The way to do this is by using the Bulb setting. On some cameras, such as my EOS 5D Mark II, this is represented by a B on the Mode dial. On others, you have to set the camera to Manual mode and set the shutter speed to Bulb (it’s next to the 30 seconds setting).

Bulb lets you keep the camera’s shutter open for as long as you like. The shutter will stay open as long as you hold the shutter button down.

If you hold the shutter button down with your finger you’ll get camera shake. The way to do it is with a cable release or remote release. If you buy a cable release, get one with a lock on it so you don’t have to hold the button down throughout the exposure.

I use a remote release. I press the button down on the remote release and hold it for a couple of seconds. When I release it the camera keeps the shutter open until I press the button again.

The camera keeps count of how many seconds have elapsed. The figure is displayed on either the LCD panel on top of the camera or on the LCD screen on the back, depending on which camera you have.

Tripods

For successful long exposure photography you need a good quality aluminium or carbon fibre tripod and a ball and socket head. I use a Giottos tripod and I’m very happy with it. Manfrotto also make good ones and so do Gitzo if your budget stretches to it. Really Right Stuff makes accessories such as L brackets to help keep your camera steady.

I never extend the centre column when I’m shooting long exposures, as it makes the camera less stable. Still conditions are best so that the wind doesn’t disturb the camera. If there’s a breeze I stand between the wind and the camera to minimise disturbance.

Neutral density filters

Light Craft Workshop 9 stop neutral density filter

The other accessory you need for long exposure photography is a neutral density (ND) filter. Even at ISO 100 and f16 (I tend to avoid f22 because diffraction can make the image softer) the light needs to be very low to obtain shutter speeds of one minute or longer, which restricts you to shooting in the late evening.

I use a 9 stop neutral density filter made by Light Craft Workshop (pictured above). Lee filters make a 10 stop neutral density filter (the Big Stopper) and various manufacturers make 3 and 4 stop ND filters.

With a 9 or 10 stop neutral density filter you can take long exposure photos much earlier during the day. They extend the window of shooting time you have.

Neutral density filters make the viewfinder go darker. To get around this, compose the photo, then attach the neutral density filter afterwards.

An alternative method, if to use Live View (if your camera has it). The Live View feed brightens the image to compensate for the neutral density filter. This works until ambient light levels drop to the point where the camera can no longer adequately brighten the image.

Technique and composition

The best way to shoot long exposures is to use the Raw format. This allows you to expose to the right and obtain maximum detail in both highlights and shadows (I write about the expose to the right technique in my ebook Understanding Exposure).

Another benefit of Raw is that you can adjust the white balance and apply noise reduction in post-processing. You can also create both colour and monochrome versions of the same image if you wish. You’ll get better quality black and white conversions from a 16 bit Raw file than an 8 bit JPEG.

There is a long exposure noise reduction option in your camera’s Custom Functions menu. This is intended for use with JPEG files only.

The disadvantage of this method is that the camera takes two consecutive exposures when you use it. The first is the photo, the second is a ‘dark frame exposure’ – a photo taken with the shutter closed so that the only thing recorded in the frame is fixed pattern noise. The camera then ‘subtracts’ the noise generated in the second image from the first image to reduce noise levels.

The second exposure is the same length as the first, effectively doubling the time required to take a photo. You lose valuable time that would be better spend creating images while the light is beautiful.

If you use low ISO settings (such as 50, 100 or 200) I doubt you will see any noise. I’ve used these ISO settings on my EOS 5D Mark II while using shutter speeds several minutes long and the images are noise free.

Noise only becomes an issue at high ISOs, or if you underexpose the image. Images taken with older EOS cameras are more likely to be noisy than those taken with newer ones.

Long exposure images tend to work best when the composition is simple. Some photographers simplify further by converting the images to black and white and cropping to the square format.

Calculating exposure

In low light, or with a neutral density filter fitted, an easy way to calcuate exposure is to raise the ISO to 3200 or 6400, select aperture priority, set the aperture you want to use (f16 is a good start) and then take a photo. Check the histogram (remember to expose to the right) and adjust settings if required. You can then calculate the exposure required at a low ISO.

For example: If the optimum exposure is obtained with a shutter speed of 2 seconds at f16 and ISO 3200, then reducing the ISO to 100 (a reduction of five stops) means that you’ll need a shutter speed of 64 seconds.

Remember that if you’re shooting in the evening, you need to adjust the exposure as you go along to compensate for the drop in light. I check the histogram after I take each photo and increase the exposure by a half stop or so as required.

An interesting phenomena I’ve encountered here in New Zealand is that it gets dark very quickly in Auckland, compared to northern European countries, as it is closer to the equator. You can actually see it getting darker, as if someone is turning the light down with a dimmer switch.

It means that if I’m shooting long exposures, the ambient light levels can drop far enough during the time the shutter is open to affect the exposure. I have to anticipate this as I’m calculating exposure (not easy).

Seascapes

Seascapes are a common subject for long exposure photography. Long exposures work best when one of the elements in the photo is moving, such as the sea, and contrasted against still elements like rocks, piers and cliffs. Seascapes offer nearly limitless opportunities for interesting long exposure photos.

Another popular subject is architecture – contrasting buildings against clouds moving in the sky.

You can also try painting with light – I wrote a short article about it here.

Read my interviews with Andy Brown and Xavi Fuentes for inspiration.

You can also look at the work of Nathan Wirth, Joel Tjintjelaar and Jeff Gaydash for more ideas (links to Flickr photostreams).

Understanding Exposure

I explore the topic of exposure in more detail in my eBook Understanding Exposure: Perfect Exposure on Your EOS Camera. Click the link for details.

Understanding Exposure cover

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