Electronic Guidebook for High-Speed Flash Photography

revised 12-00

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Activity 16. Speed of a balloon rip

 

Equipment needed:

2 Vivitar 283 flash units

8 AA batteries or 2 SB-4 AC adapters

2 cords to connect flash units to sound triggers

2 flash clamps

High-frequency clock (such as the clip clock)

Electronic stroboscope

2 piezoelectric sound triggers

Meter stick and protractor

Large balloon, preferably cylindrical

Needle or pin

Note: Before doing this activity, try Problem 2 in Appendix F for practice. The photograph for that problem will also help in setting up the experiment.

1. The setup for this activity is similar to that of the previous one. Inflate a large balloon and place sound triggers at both ends of it. Situate the clock disc above the front edge of the balloon and as nearly parallel to the film plane of the camera as possible. (See the photograph in Appendix F.) Place both flash units next to each other and just to the right out of the picture. The reason for this placement is so that the shadows cast by the rips will contrast with the rips themselves. Use the yellow automatic range, and close the lens aperture one stop from that indicated by the calculator dial. This corrects for the fact that the balloon will be illuminated by two flashes of light.
2. Prepare for a photograph and puncture the balloon near the left end. Make an enlargement of the negative and determine the speed of the rip according to the method of Problem 2. (Remember, you will need to know the diameter of the clock disc.)

Note: If you take photographs with a Polaroid camera, see Appendix C for suggestions. In determining exposure, remember that in this experiment each exposure results from two flashes of light.