March 15, 2015

Canon Point-and-Shot Camera / Time-Lapse Photography

Capturing the visual experience of the flight is a given for most balloon hobbyists. As virtual astronauts, we of course we want to share the excitement and fun of the adventure with others – so pictures or videos are a must.  But launch presents a dilemma - capturing great images is pitted against the risk of loosing expensive photographic equipment from failed payload recovery.  Simply stated, we want to take great images with equipment we can afford to lose.




One solution is to buy a used a Canon A1100 - a so-called point-and-shoot camera. The A1100 is a popular camera, offered frequently on eBay for less than $50. With 12+ megapixels, it does a decent job of capturing images – albeit not HD.  And its not overly heavy. With lithium batteries installed, it comes in at about 120 grams – an acceptable weight for most payloads. 

Why a Canon point-and-shoot over other point-and-shoot brands? Canon cameras have a large following of hackers that have found ways to enable a powerhouse of features beyond the camera’s standard out-of-the-box capabilities. The scope of functionality enabled by hacker firmware is amazing and free to use! See more here. For balloon enthusiasts, the most important capability is time-lapse (Intervalometer) function– enabling the A1100 to automatically take a picture every few seconds. For balloon flight, the time-lapse feature allows an entire mission to be recorded on an SD card.


Needed:

Canon Powershot A1100 IS (other point-and-shoot Canon's may work as well)
SD Card – 32GB or more recommended
A laptop computer
Optionally: SD Card Adapter / USB interface

General Overview: 

Hacker firmware (CHDK) is loaded on to your camera via its SD card.  The firmware is first downloaded on your laptop, and then transferred to an SD card. The SD card is removed from the laptop and placed in the camera.  Upon start-up, the camera reads the SD card and substitutes the hacker firmware (temporarily) in place of the camera’s normal operating system. The hacker firmware provides menus to start the time-lapse function.

Steps to Enable Time-Lapse Capability on an Canon A1100 IS:

With a Canon A1100 in hand, you will want to find out the exact model / year / production copy of the camera.  This information is needed to download the correct version of Canon hacker firmware – referred to as CHDK. Luckily there is an online app that can help you do this, along with putting the right version of CHDK firmware on your SD card.

(1)  Start by putting in a new / empty SD card in your A1100 IS
(2) Take a single picture (not a video)
(3) Download “Stick” - a free app for your laptop (the author does ask for a $1 donation if you find the app useful): Download by clicking here.
(4) Move the SD card from the camera to your laptop (you may need a SD / USB Card Adapter depending upon the model of your computer)
(5) Double click the downloaded file to open the folder
(6) Run the "Stick" app by double clicking on stick.jar (must have Java installed)
(7) Open the SD card to find its contents
(8) The photo you took should be found in the folder DCIM
(9) Drag the photo from the SD card to the app “drag photo here” box
(10) Click “Download” on the Stick app screen
(11) Click “Scan for Card” on the Stick app screen
(12) Click “Permission to Prepare Card”
(13) Name the two partitions: Partition 1: PHOTOS  Partition 2 : CHDK
(14) Click “Install CHDK”
(15) The SD card will now be formatted into two partitions
(16) Click “Safely Eject SD Card”
(17) Slide the SD Lock on the SD Card
(18) Exit the "Stick" app

The CHDK firmware needs a time-lapse function script.  There are several scripts available online that can do the job (search Google for Canon intervalometer scripts). Here is a simple one to add to your SD card:

Steps to install time-lapse (intervalometer) script

(19) Download time-lapse script from here which points you to this link.
(20) Move the downloaded file “counter.bas” to the file folder on the SD card called PHOTOS/CHDK/SCRIPTS
(21) Eject the SD card from the computer
(22) Load the SD card on your camera

Now, upon turning your camera on, you will have new firmware.  There are a few menu steps to enable the time-lapse function:

(23) Turn on the camera with the “>” button
(24) Press the “*” print button
(25) Wait for a couple of seconds
(26) At the bottom of the screen is “Default Scrip  ALT”
(27) Press the camera’s function-set button (center of the “navigation wheel”)
(28) Use the navigation wheel scroll down to “load script from file” line
(29) Press function-set
(30) Scroll down to find “counter.bas"
(31) Press function set
(32) The menu will return to the script menu (scroll down to the bottom to “countdown intervalometer)
(33) Select the “Interval in Sec”  using the wheel left or right to move values
(34) Select the “Number of Shots” using the wheel left or right to move values
(35) Scroll down to the “back” line item at the bottom of the menu
(36) Press function-set
(37) Half hold the down the shutter button – starting the time-lapse shooting!
(38) Press the main “on/off” button to stop the process


There is a process to combine the of time-lapse photos to make a movie – using a GoPro app.  A separate post will tackle this topic. 


Below is a test video shot on the morning of St. Patrick's Day 2015: The time lapse is from 7:44 AM until 8:50 AM - 66 minutes with a picture every 12.9 seconds.  A total of 308 frames were used to make a 30 second movie - using each frame roughly three times. Music provided by Earth, Wind, and Fire.





One of the limitations of the A1100 is the number of shots possible on two AA batteries. The Canon specs call out a limit of 140 shots with a set of normal alkaline batteries, and 350 shots with NiCa. Lithiums give double the battery life. In experimenting with a set of lithium batteries, 500 - 700 pictures can be captured before the batteries die. From a practical standpoint, this means that  a typical balloon mission lasting about 150 minute (2 1/2 hours) could be fully captured by setting the time-lapse to 15 seconds before depleting the lithiums.  Unfortunately, the short battery life limits a mini-movie to 20 to 40 seconds in length.


Jeff in Workshop

Jeff in Workshop
Working on Payload Called "Aunt Bea"