The art of light: how to shoot light trail images
Capturing beautiful streaks of light are a great way to bring a different feel to your cityscape or landscape images. Pro photographer Kieran Stone breaks down how it’s done.
When it comes to photography, almost any shutter speed could be considered a long exposure depending on the chosen subject matter. As objects move, their speed in relation to your shutter time ‘burn’ their motion into the sensor/film over the distance they’ve traveled.
This is the case for anything moving, regardless of the speed of the subject - clouds, people, water, a snail or even the motion of the earth, can all be blurred with the right shutter speed choice. This blurred motion you see in the image also becomes more apparent when the moving subject is much brighter than the background it is passing.
One of the best ways to practise with long exposures, and understand the fundamentals of what is going on, is with car light trails.
The best place to shoot car trails is from an overpass or bridge over a busy road. Two way traffic with multiple lanes will give you the white headlights coming towards you and the red tail lights going away from you, and positioning yourself between the two will give a good balance of both.
However, just having car trails in the shot is ok for practising and learning, but if you want to get a strong image as well you’ll need a good background at the vanishing point of the road.
Use the trails as leading lines towards something: buildings, a mountain, another bridge, anything really, as a featureless horizon is much less captivating for the viewer.
Once you learn how to predict how the car trails will be in the image you can look for more interesting and unique angles. Shooting from a low vantage point on the side of the road, or a mountain lookout where a road is visible, or even from a tall building can all add something different to your image.
There are lots of different ways to utilise the light trails to create lines and curves that provide depth and dimension to an image.
You don’t have to stop at cars either. Anything moving at night that has lights will work too and look completely different. Trains are great for this as they are long and follow precise paths. Getting close, but not too close, to train tracks such as a level crossing means you can get the full length of a train to block the background, creating interesting lines with the train itself and the interior lights.
Boats and ferries, such as those at Sydney’s Circular Quay, will reveal paths in the water that can’t be seen without a long exposure. Different size boats will have overlapping lights, giving the image a three-dimensional look. Even a bike path can be used with flashing tail lights creating a dotted line of light floating in the air.
The easiest way to capture car trails is at peak darkness. The light is going to be dark enough for car lights to be on and stand out, and be consistent enough that you can use multiple exposures to build up the effect in post production, which I’ll cover later. Shooting at night also means you don’t need filters to get exposure times of 30 seconds or longer.
However the most interesting time to shoot is just after the sun has gone down. There will still be colour in the sky and most peoples headlights will be on. You might not be able to get as long of an exposure without filters, but the overall light will be much better for showing detail in other parts of your image.
You can always keep shooting as the light fades and gradually increase your exposure time to compensate. Once the sky has turned too dark, you can lose any interest in the background. Even if buildings have lights on, they can get lost a little bit against the sky. Shooting just after rain will add an extra glow to the road as well.
Finally shooting at sunrise or before is not recommended. Usually there is less traffic at this time and as the light increases you won’t be able to capture light trails.
Although it’s not impossible to shoot long exposures and car trails without a tripod, it does make it much easier and gives you more opportunities with composition. If you want to start out with the bare minimum though, you’ll need a stable surface to rest your camera on so it doesn’t shift or shake for at least 30 seconds. A tripod is just a steady surface you can take anywhere and adjust the camera angle how you like.
Another useful piece of equipment is a cable or remote shutter. This way you don’t have to touch the camera, and potentially get camera shake, when you press the shutter. Again, you can get away without one by using a two second delay on the camera shutter to avoid movement when pressing the shutter. However one benefit of the remote shutter is that you can time your shots with the flow of the traffic, which is much harder to do with a delay.
Neutral density filters can come in handy when shooting closer to sunset. Even a 3 stop ND filter will push your shutter speed from say four seconds to 30 seconds. Graduated filters have their place here too, for example using them upside down can help balance out the bright headlights or street lights with a potentially darker sky or background.
Having the right shutter speed for the location you are shooting is important, but if in doubt, remember that longer is better. If your shutter speed is too short, the car trails will appear as disjointed lines on the road rather than a continuous streak. How short is too short will depend on the road you’re shooting.
As a test, I like to count how many seconds it takes for a car to come into the frame until it reaches the vanishing point or exits the frame, and then use this as an ideal minimum shutter speed. If you can’t get this shutter time with your lowest ISO and most closed aperture, then use ND filters, or wait until the light fades more.
Ideally you’ll want a low ISO, the lowest your camera will go, and a midrange aperture, about f8-f11, to capture the sharpest details. Closing down your aperture further will allow you to keep your shutter open longer, however the trade-off is a loss of sharpness as a result of a phenomenon called diffraction.
If in doubt, use Shutter Priority mode to keep your shutter speed consistent, and aim for an exposure 1-stop under what the camera thinks is correct. This is because the camera will attempt to meter for the dark scene and try to expose it more. With a night time shot, this will only over expose your main subject (the lights).
When shooting at peak darkness, you can tend to shoot a little longer as the dark background won’t add much more light to the image over time compared to the light trails. If your camera only allows you to shoot a maximum shutter speed up to 30 seconds then you’ll need to shoot in Bulb mode to shoot longer exposures.
Timing is important when shooting near traffic lights. Wait until all the cars are moving before taking a shot. If you start to exposure just as a light turns green, you will get ghost images of cars at the back that haven’t started moving yet. It’s best to pick a location where there is a constant and steady flow of traffic, as peak hour bumper to bumper traffic will not be effective.
If your shutter speed is too long and there is very little traffic, the white of the headlights will start to turn yellow, and the red will become less noticeable as the background becomes brighter. On the otherhand if there are too many cars, then the headlights will all blend together as a solid white patch. To build up the amount of car trails in a scene, it is best to take a few shots at the optimal shutter speed and then stack them together in post production.
Finally check your histogram to make sure the exposure is correct. It should be weighted to the shadows and blacks with a tiny bit of clipping in the whites.
If it is too bright and clipping too much then the headlights will all merge together and create a solid white patch. Because you are shooting when it is dark, it’s not a problem if there is a little bit of clipping in the blacks.
If you are just doing small adjustments to your image there are a few things to keep an eye on.
Remember that bringing down your highlights and whites too much in Lightroom can create a muddy look to what should be the brightest part of the image.
Check where the headlights are brightest by holding down “alt” (windows) or “option” (mac) while moving the highlights or whites slider. This will show where the image is clipping. Allow a tiny bit of clipping in the brightest area. The centres of street lights will most likely be blown out too, this is to be expected.
Besides the basic exposure and colour corrections, there are ways to maximise a car trail shot with post production. You will need to plan for this while shooting though.
Once you work out the best shutter speed for your location, try taking multiple shots at the same settings and exposure level. Each shot will be slightly different as not everyone takes the exact same path along the road. Once you have these exposures, from two to about 10 depending on the amount of traffic, you can stack them as layers in Photoshop and change each of the layers blending mode to “Lighten”.
Doing this will only let the pixels that are brighter than the layer below shine through. If the sky, or anywhere else in the image, is adversely affected by this you can create a layer mask to block out those areas. Using this method lets you turn any road into a busy highway.
Roads can be very dirty places when you really start to look at them. Use a healing brush to clean up any rubbish, potholes or any other distracting features on the road. If it doesn’t add to the image - remove it.
Long exposures can be notorious for hot-pixels too. These will be tiny white, red, green or blue dots in the image. You won’t see them unless you zoom in to 100% and they can be easily removed with a small healing brush.
You may not care about them if you are just sharing on social media, but when you go to print your image and frame it, you’ll be kicking yourself for not checking for them earlier. They are the simplest thing to remove and the only thing you’ll be able to see if you don’t!
Car trails are something you can have a lot of fun with. Seemingly boring roads can turn into amazing features in your photographs by utilising the motion of the cars and their lights. The principal elements mentioned here can be adapted to any movement of light, either emitted or reflected. Trial and error will build up your understanding and help you develop a keen eye for how movement is translated to a single long exposure frame. Shoot long and prosper. ❂