Creating star trails is a well known technique in Astrophotography and the same technique can be used to create trails of activity during the day. The results are both unique and potentially useful to identify heavily used routes or flows in urban areas.
You will need:
1 x Timelapse System, you can use a simple webcam as per our previous Tutorial: Torch + Webcam = HD Timelapse System a DSLR such as the Canon G9 with CHDK , a iPhone with the free Gorrilacam app or any camera that can take photos at regular intervals.
1 x Copy of Photoshop, you can download a 30 day trial.
Time Taken, 2 Hours (including capture and processing).
The concept is simple, set up your camera, webcam or iphone at a suitable location, and capture an image at regular intervals, for our example we captured an image every 2 seconds pointing down at a London street:
We left the camera running for an hour capturing 1800 images, saved into a folder on our computer.
The next step is to open photoshop and start stacking the images.
Image Stacking in Photoshop
The images will be stacked onto of an intially blank image via a simple automated action:
1) Create a new blank black image the same size are your captured photographs.
2) Load the action into the action windows in Photoshop and load the action Startrails.atn.
3) In Photoshop click ‘File’, ‘Automate’ and ‘Batch’. Select the action you have just loaded and choose your directory with the images as source and make sure you select ‘None’ for the output directory.
Click ‘Ok’ and leave it running, our Mac laptop took around an hour to stack the images – resulting in the ‘Day Trail’ below:
You can clearly see the path of the traffic and the most utilised sections of the walkways over the hour, we simply like the effect.
We have created a Day Trail pool on Flickr if you create a stacked image feel free to add it to the pool…