How to use your camera's B setting

Words by Roger Payne

B is one of photography’s hidden gems. It’s a feature that you’ll find on almost every SLR – digital or otherwise – but is one that hardly gets any use; program modes and increasingly wide shutter speed ranges have seen to that.

But if you’re one of many photographers guilty of B neglect then you’re also guilty of closing the door on a wealth of low-light picture-taking possibilities. So, as we hurtle towards long, dark nights, we thought it was high time we explained just why you should learn to love that setting at the dark end of your shutter speed range.

First, though, a brief history lesson. B stands for Bulb and has been around on cameras since the late 19th century. Put simply, B enables you to keep the shutter open for as long you choose; the term ‘bulb’ refers to the shutter mechanism on the cameras of the time where an air bulb was squeezed to open the shutter and then released to close it. The principle remains the same today, only now you’ll typically find your camera’s B setting by selecting the manual exposure mode and heading into the long shutter speed settings.

With the B setting chosen, you’ll need to amass a few extra bits and pieces before you venture out to take pictures. But the digital SLR users among you will need to check a few camera settings as well before you start. First, make sure that you can manually set the ISO, rather than leaving your camera to do it. DSLRs with Auto ISO settings are all well and good, just not when working with B. In low light, Auto ISO modes are likely to select a high speed, which will create extra noise in your images. Instead, set the ISO manually – 100 or 200 for the best quality.

Second, seek out your DSLR’s long exposure noise reduction feature. It will almost certainly be buried in a sub-menu or custom function setting. Now you’ve found the feature, you have to decide whether you want to use it. It has potential quality benefits but there’s a big downside too. In-camera noise reduction (NR) works by the camera shooting a ‘dark frame’ to identify the position of noise.

However, this usually takes the same time as the actual image exposure and the camera locks up during that time. If you have been sitting there for a 30-minute exposure for a star trail image, the prospect of waiting another half-an-hour before being able to take another shot might not appeal. One way round it is to use noise reduction for the last shot of the night so the camera can do its thing on the way home.

Finally, I’d advise you to shoot your B images using the Raw file format rather than JPEG. With light pollution, street lighting and so on, the camera’s white-balance feature might need a helping hand and being able to do this in post-production is a distinct advantage, hence shooting Raw.

Naturally, we’re expecting most of you to be shooting digital, but using B is one occasion where film is actually at an advantage. Granted, you can’t instantly assess how accurate your exposures, focusing and composition are, but if you load up with an ISO 100 emulsion you’ll avoid the noise you’ll get with digital.

When it comes to the actual picture taking, the basic principle remains the same. Select B and much of the wonderful automation in a camera turns off. There’s no metering to help you out – exposure comes down to guesswork on your part – while autofocus will falter in very low light so you’re advised to shoot using manual focus, coupled with a small aperture of f/16 or f/22 to maximise depth-of-field and combat focusing inaccuracies. Of course, selecting a small aperture does increase exposure time – for example, an exposure of 60 seconds at f/2.8 becomes a massive 32 minutes at f/16.

One technique to use to aid manual focusing is to shine a bright torch at the subject – this mightn’t be appropriate or practical but it’s an idea. Naturally, the more B images you shoot, the more accurately you’ll be able to assess how light levels translate into minutes or even hours of exposure, but expect a lot of duff shots when you start shooting in B. You can start taking B images without even leaving your house. Wait until night-time and you can shoot simple subjects like flames on a fire, gas rings and candles. Be sure to try a variety of exposure lengths.

Download the images and take a look at the results. It’s a good way of assessing if your tripod is steady enough and your camera’s noise performance – try shooting with and without noise reduction and compare the results. With a small torch, try locking the shutter open, then tracing the torch around the outline of an object, or trying to draw a shape in the air – just as you used to with a sparkler as a kid. As the shutter is open, it’ll record the torch movement, so move it slowly and smoothly to get the best results.

Once you’re confident that your technique is sound and your tripod sturdy, then venture into town. Floodlit buildings and illuminated signs are an obvious choice and work well with the B treatment, but often introducing a moving element into your shots is where B really scores. For this reason, traffic trails are a must but, like most subjects, require some thought to capture well. First, you need to find a good location, which can be done during the day. Many photographers head to a bridge over a busy motorway or dual carriageway.

This is OK, but cars coming past on the bridge can cause camera shake even with your gear firmly mounted on a tripod. A footbridge might be better but some ‘bounce’ as pedestrians walk over so watch out for this. Finding a spot facing west is also advised as after the sun has set, some light will remain in the sky, which is preferable to a black, featureless sky. Finally, pick a curved road to make the resulting image more interesting and, if at all possible, shoot a stretch that doesn’t have street lighting or traffic lights as these can dilute the blurred car light effect.

Once you’ve cracked all that, the technique is the same; f/16 or f/22 and then a wide selection of timed exposures. For traffic trails, start at around 20 seconds and shoot anything up to five minutes. A small piece of black card will come in handy. Hold it in front of the lens if there’s a risk of a car’s headlights shining straight into the lens.

The fun with B really starts if you photograph subjects where you have to provide the illumination yourself either with flash, a powerful torch, or a combination of the two. Such a technique can be used to light up churches, derelict buildings, windmills and even farm machinery. If you’re going to try this ‘painting with light’ technique, your work should start when it’s still light when you can check access and find a suitable spot to leave your car.

As exposures will run into many minutes, you should avoid windy nights as this will cause even the sturdiest set-up to suffer from camera shake. In addition to the flash/torch you’re going to use to light up your subject you’ll need some additional lighting to help you find your way around. A head torch is a good idea, leaving your hands free to change camera settings, while a wind-up torch means that you aren’t reliant on battery power.

Once you arrive at your location, set up and use the powerful torch to light up the subject and help you focus. If you want to take a test shot to check focusing and composition, set your ISO to its highest setting and take a quick snap, then set it back to ISO 100 or 200 when you’re happy that framing and focus are right.

When you’re ready to start the exposure for real, set the aperture on the flashgun to match that set on the lens. Now, start the exposure and fire the flashgun with its test button. Wait for it to recharge then fire it again, repeating this as many times as you see fit. You’ll be surprised how many flashes a large object needs, but be sure to distribute your bursts evenly and don’t just concentrate on the building itself, fire some additional bursts to light the foreground too.

Be careful not to stand in between the camera and the flash when you fire it as you could appear as a ghostly silhouette and also make sure that the flashhead is pointed away from the camera. Finally, if your flashgun has a lit LCD, mask it off, along with any LEDs. You might also want to take some coloured filter gels to place over the flashhead.

It can be a long night shooting B images, but your work isn’t finished when you pack up and go home. Once you’ve downloaded your images onto a PC, run them through noise-reducing software such as Noise Ninja or Neat Image to maximise picture quality. Despite all the hassle, though, the B setting affords untold levels of creativity and once you’ve mastered the basics, you can soon start perfecting your technique to create truly stunning results.

KIT BAG

Long exposures necessitate good support so you need a sturdy tripod for your B pictures, but that’s not all. A remote release cable is essential to enable you to hold the shutter open. For particularly long exposures, it’s advisable to get a lockable remote release so you don’t have to keep your finger on the button for the duration of the exposure. You’ll need a dedicated remote release for your camera – your camera’s instruction manual will tell you the correct accessory.

An extra battery for your camera (and flashgun) is also advisable. Locking the shutter open eats up batteries, plus long exposures make for extended write times as the image is transferred from the buffer to the card.

There are also a few non-photographic items that will come in handy. A small torch will help you check and change camera settings, a big torch for painting with light and helping with focusing, a stopwatch will keep a tally of exposure time and, clothing wise, you should wrap up warm. A Thermos of hot chocolate won’t go amiss either.

Finally, it’s worth taking someone with you. If you’re moving around firing a flash during your B exposures, they can guard your gear, plus you’ll have safety in numbers.

TECHNIQUE

Shooting long exposures digitally with the B setting increases the likelihood of your images suffering from hot or stuck pixels. The longer the exposure, the more likely you are to get some and they manifest themselves as a bright spot on the image. A hot pixel will be white while a stuck pixel will be red, blue or green but it could be cyan, magenta, or yellow.

Hot pixels occur because of charge leakage from individual pixels on your DSLR’s image sensor. Essentially, the sensor is electrically charged as the picture is taken and this charge can sometimes transfer from one pixel into another, causing it to brighten abnormally. Sadly, hot pixels are a fact of long exposure digital life, but they can be simply retouched in imaging software.

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