Following the construction of my camera slider, I thought I would share a bit more information about the materials and how to use it.
First let’s talk about the purpose of such device. The goal here is to capture images of a scene at regular intervals (30 seconds for example) from a moving point of view and group these pictures in a timelapse movie. The effect created here is a bit like you’re moving slowly into a really fast paced world.
An excellent example of what you can create with it is the following video:
Building the slider
There are lots of camera slider models on the internet, some with detailed instructions, some with a lot of options. The one I built is far from matching the quality of professional sliders but it has the advantage of being cheap and going the job I need it for.
Here’s a list of the materials used:
- 1 Rail from a straight-edge board clamp (similar to this) $30
- 6 Ball bearings from a roller/skateboard store $15
- 1 DC motor .5 rpm 6v from SDP/SI (ref A 3Z16-0005B) $22
- 2 Gears 11 teeth from SDP/SI (ref A 6A16-011DF2504) $16
- 10 feet timing belt from SDP/SI (ref A 6Z16-C025) $26
- 1 timing belt connector from SDP/SI (ref A 6M16M060) $5
- 2 tripods with detachable plates $60
- 1 4 AA batteries case from the Source $5
- 1 tripod head (can vary a lot depending on quality and weight of your camera)
This brings the overall bill of materials to about $170 (without the tripod head) which stays pretty low compared to commercial sliders.
Using the slider
Using the slider is really easy. Here are the main steps:
- Set the tripods to the desired height
- Attach the rail to the tripods
- Bring the carriage to the starting end of the rail
- Attach the camera
- Set the focus on manual, and set the various parameters of your camera
- Attach your timer to the camera
- Set the timer to the desired interval (ex: 30 seconds)
- Start the motor
- Start the timer
After a couple of hours, the camera should be near the other end of the rail. Stop the timer and the motor. You can now download the images sequence on your computer.
I use a linux operating system which has a few convenient tools to generate movies from still images. The tool I am using is avconv which is part of the libav software.
avconv is a command line tool. This is the command I use to generate a timelapse movie:
avconv -f image2 -r 20 -i /home/thomas/Timelapse/IMG_%04d.JPG -start_number 96 -vcodec libx264 -b:v 12000k timelapse.mp4
-f image2 means we are working from images
-r 20 means the rendered video will have 20 frames per second
IMG_%04d.JPG is the naming format of my image files
-start_number 96 means my image sequence starts at IMG_0096.JPG
-vcodec libx264 means the video will be encoded using the h264 codec
-b:v 12000k is the video bitrate. High bitrate = high quality = big file size
timelapse.mp4 is the name of the video that will be created
This is the result of this command:
The camera settings still need to be tweaked to accommodate the change of luminosity. I will also need to test it on the night sky during winter to know how long the batteries can last.
Update: October 19th 2014
Here is a first try on the night sky. There was a moderate aurora at the beginning of the night which subsided by the time I started to take pictures. The clouds also started to roll in at the same time. The video is not great but it teaches me that I need to run more than 45 minutes to get that “moving” effect and I also need to get the foreground closer.