Protocol Development and Description

 
 
 

  1. (1)Laser pointer - see discussion below, we found a weaker, less bright laser pointer to yield better results than a bright powerful beam over the long exposure

  2. (2)Camera - Canon S90 modified with firmware from the Canon Hack Development Kit (CHDK) to allow long exposure times. Please see http://chdk.wikia.com/wiki/S90 and additional details on our Resources page for further details.

  3. (3)Tripod - Critical to ensure that the long-exposure photographs are not too shaky/fuzzy. We used the Joby GorillaPod Flexible Tripod available at local retailers and Amazon.com

  4. (4)Dark Room with white/blank wall- For the long exposure photographs to capture the postural sway of the laser pointer, the room experiments are conducted in must be absent of all light aside from the laser pointer’s beam. For ease in comparing results, a white wall is the optimal surface to shine the laser pointer against.

 

Necessary Equipment:

  1. (1)Set up the camera with the following settings to enable a 32 second exposure:

    Main Camera Settings:

  1. •Tv -> shutter speed priority

  2. •Tv = 32

  3. •tuned to +2 Iso/Auto

    CHDK Extra Photo Operation Settings:

  1. •Disable Overrides = OFF

  2. •Override Shutter Speed = 32

  3. •Value Factor = 1

  4. •Shutter Speed Enum Type = EV Step

  5. •Step Size = 4 EV

  

  1. (2)Attach Laser Pointer to Test Subject:

  2. The laser pointer should be set to be permanently “on” through any means available (we used tape to hold down the button). With the laser on, we mount the pointer onto a convenient location on the test subject as close to their center of gravity as possible. For the initial experiments we simply held the laser pointer in hand to verify the long exposure photographs would develop and demonstrate evidence of postural sway. For the team trials we taped the laser pointers to the outer hips of the test subjects.


  4. (3)Mount Camera on Tripod and Set Up in Dark Room:

  5. Test subjects stand approx 6ft from a white wall in the dark room and prepare for test trials. See figure on the left for schematic of test setup.


  1. (4)Conduct Tests:

  2. The test subject will try each of the following conditions for ~30 seconds while the camera is elapsing:

  3. (a)Standing On Both Legs, Eyes Open (baseline conditions)

  4. (b)Standing On Both Legs, Eyes Closed

  5. (c)Standing On Right Leg, Eyes Open

  6. (d)Standing On Right Leg, Eyes Closed

  7. (e)Standing On Left Leg, Eyes Open

  8. (f)Standing On Left Leg, Eyes Closed

  9. Additional complexity may be added by varying arm placement or adding other variables during testing - this exploration is left to the curious experimentalist at their own discretion!


  11. To set up each trial, instruct the test subject to assume the appropriate test condition (one leg or both, eyes open or closed) and to remain still as the camera shutter is depressed and the long-exposure photo is taken over 30 seconds.


  1. (5)Analyze Results:

  2. Compare qualitatively the results for each test subject across conditions (a) through (f) and between each test subject overall. Discuss and conjecture reasons for variation based on knowledge of physiology!

Experimental Procedure: