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5 Easy Steps to Merge Light Trails in Digital Photo Professional

Light trails are a fun and easy way of adding dynamism to nighttime urban photographs, but depending on traffic conditions, they may end up looking sparser than you want. A photographer shares how he achieved the image below, including how it was merged in Digital Photo Professional! (Reported by: Yuta Nakamura, Digital Camera Magazine)

EOS 6D/ EF16-35mm f/4L IS USM/ FL: 25mm/ Aperture-priority AE(f/11, 15 sec)/ ISO 100/ WB: Tungsten

1) The shoot
2) The merge


The shoot

The subject and composition

I found this retro-looking building that looked like it was full of history right in the middle of the city. It would have made a good picture on its own, but its location right at the crossroads inspired me. So, I decided to incorporate vehicle light trails in front of it so that the image blends the classical with a touch of modernity.

I placed the building smack in the centre of the frame. Then, observing the flow and direction of traffic, I angled the shot to capture the criss-crossing light trails on the main road in front.

To get the appropriate length of light trails, I set the shutter speed to 15 seconds. I narrowed the aperture and reduced the ISO speed to compensate.

Why do a merge?
Due to the timing of the traffic lights and the rather sparse traffic, I wasn’t able to get the light trails to look as dense as I wanted.


The merge

Step 1: Open your base image in Digital Photo Professional

For an easier workflow, choose the images that you want to merge and put them into the same folder. Decide on which image you want to use as your base (the “background image”). Then, open it in Digital Photo Professional.

The background image

Also see: 5 Essential Adjustments to Do with Digital Photo Professional


Step 2: Go to ‘Tools’ → ‘Start Compositing tool’


Step 3: Choose the foreground image and the composite method

(1) Foreground image

The foreground image is the image that will become superimposed top of the background image.

I chose an exposure with different light trail patterns from my background image:

(2) Composite method

The composite method determines how the images will be combined. Here, I chose ‘Lighten’, which combines only the parts of the foreground image that are brighter than the background image. It works because we want to layer only the light trails, which are bright.


There are five different composite methods in total. The other four are:


The pixels of the foreground image are added to the background image. 

- Average

The pixels of the background and foreground images are combined with each other at 50% opacity each.

- Weighted

Allows you to adjust the proportion (opacity) of the foreground image in relation to the background image.

- Darken

Only the parts of the foreground image that are darker than the background image are combined.


Step 4: Repeat Step 3

By default, the tool aligns the centres of the background and foreground images. You can use the position arrows to adjust the position of the foreground image if necessary. I didn’t need to use them here.

Click ‘Continue’ to add the next exposure and repeat Step 4 again. I used ‘Lighten’ for the third exposure, too. Repeat this step for each foreground image that you want to composite.


Step 5: Save the image

When you’re done, click “Save As” to save the output. Enjoy the results of your merge!


Know this:

1. The final composited image takes the same colour space as the background image.

2. The merged image will be in JPEG format. But you can also do a composite in RAW format if all the images meet the following conditions:
- In RAW format
- Shot with the same camera model
- Have the same ISO speed and highlight tone priority settings.
- Same original image size

Find out more about what you can do with DPP in:
RAW Image Processing: How to Bring Out the Blue in Blue Hour Photos
How to Enhance Fireworks with Digital Photo Professional
Focus Stacking: A Pro Technique Made Simpler with Focus Bracketing

For more light trail photography ideas, see:
Ultra Wide-angle Lens Technique: Light Trails from a New Perspective
Built-in Flash Techniques #5: Fast, Furious Light Trails with Second-Curtain Sync

Also check out:
3 Useful Camera Functions for Shooting Nightscapes


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Digital Camera Magazine

Digital Camera Magazine

A monthly magazine that believes that enjoyment of photography will increase the more one learns about camera functions. It delivers news on the latest cameras and features and regularly introduces various photography techniques.
Published by Impress Corporation

Yuta Nakamura

Yuta Nakamura

Born in Kanagawa Prefecture in 1988. Since 2010, he has been working as a nightscape photographer, not only shooting nightscape locations mainly in the Tokyo area but also throughout Japan. He runs the information site for nightscape spots “Nightscape FAN”