Light Trails

At this time of year it can be great fun to stand outside on a cold clear night taking traffic trail shots; although non-photographer friends probably think you’re mad.

Once you find a great location, such as Will Cheung’s choice of the Menai Bridge in Anglesey, you set up your tripod and remote release, select a long exposure and wait hopefully for a suitable steady stream of traffic.

Naturally, there’s little traffic and you end up with a moody shot like our starting image but with hardly any traffic trails. If it is quiet and you can’t set a very long exposure to allow for more cars to pass because it’s reasonably bright, take a shot each time you get a car passing through. You need the same composition so use a tripod. Here we had six originals to work with.

Back home, you can combine the best bits from the series to give that really busy traffic look. I used Photoshop CS5 for this step-by-step but the same technique will work in other image editors.

A final tip, don’t be tempted, as I was, to flip your image left to right to improve the composition. You’ll get people pointing out that everyone’s driving on the wrong side of the road.

1 Choose your base image

Open the image you want for your background. In this case I chose one with very few trails. This image will form the majority of the end result so choose one with the best lighting and sky. Open a second image with some trails to add. Choose 2Up from the Arrange Documents drop down.

2 Adding layers

Now drag and drop the background layer icon from the second image onto the original image. This adds the new image as a second layer. You can close the second image. Double click the new layer name and re-name it ‘Trail1’. Add a layer mask by clicking the icon below the layer stack.

3 Use a mask

Now we need to mask out everything except the trails we want to add. Click the mask icon to make it active, set the foreground colour to black and use the Brush tool (B) to paint the mask, revealing the background. Toggle the visibility of the mask using the \ key to check progress.

4 Control layers

Edit the mask until you’re happy with the result. Next I opened a shot which displays trails in a different area. As before I added this as a new layer with mask. Paint the mask with black to reveal just the trails. Switching off the visibility of the other layers helps you to see what you’re doing.

5 Use layer blend modes

Vary the size and opacity of your brush to blend the new trails into the other layers. Toggle the visibility of the lower layers to check progress. I wanted some trails nearer the centre so I’ve added yet another layer and mask from an image with strong trails.

6 Final step

To move the trails into position use Edit>Transform>Distort and drag the handles to position the trails. You will need to zoom out using Ctrl and – to see the handles. Hit Return to apply the distortion. Tidy up the mask, removing any hard edges with a soft brush. Keep refining the mask until you’re happy with the results.

Taken from the November 2011 issue of Advanced Photographer magazine