Activity 6. Photographing the smash of a tennis ball or racquetball
- Vivitar 283 flash unit
- 4 AA batteries or SB-4 AC adapter
- Flash-to-trigger cord
- Flash clamp
- Piezoelectric sound trigger
- SLR camera and film
- Tennis ball or racquetball and racket
- Large cloth sheet or blanket
The setup for this photograph is more involved than that of a balloon burst but can easily be done in a small room.1 A typical arrangement is shown in the overhead view below. The sound trigger should be placed as close as possible to the location where the collision of the ball and racket will occur. If one were doing a forehand shot, for example, the sound trigger could be placed on a stool or box about a foot below the spot where the racket met the ball. Of course, sufficient room would have to be left around the person wielding the racket to allow freedom of movement.
The background can be a problem if you plan to include the person swinging the racket in the photo. You may want to dispense with a hung background and simply make sure the subject is far from a wall and that distracting objects are removed from the background.
The ball can easily be stopped without rebound in a sheet or blanket hung from the ceiling or other support. Let the blanket hang freely. If it's stretched tightly, it will reflect rather than stop the ball. The position selected for the camera depends on whether one wants a side view, front view, or back view of the ball. The flash position should be selected so as to avoid throwing unwanted shadows across the ball.
|Safety considerations: Be sure that everyone stands away from the possible path of the ball. The potential for eye damage from an errant ball may be increased since the room will be dark, and one may not be able to see well enough to dodge the ball. It's a good idea not to darken the room completely. Cracking a door or a window shade won't let in enough light to affect your photos, but it will allow you to see what you're doing.|
Before attempting photographs, have the person who swings the racket take some practice swings with the room lights on. Then repeat with the lights off. If the room is too dark, a penlight can be used to illuminate the ball during the swing. The flash will probably be bright enough in comparison so that the light from the penlight is not noticeable.
Like always, prepare your data page before taking the first photograph. Then evaluate your results afterward and record your conclusions.
|The photograph to the left shows the position of the sound trigger relative to collision site. The trigger was taped to a tripod. This allowed the height of the trigger to be adjusted easily. Note that the flash is positioned to the camera's right, as evidenced by the shadows. Had the flash been placed to the left, the ball would have been in shadow.|
|Tip: Using a piezoelectric trigger for these collisions is marginal. The thud that the collision of the ball and racket makes doesn't generate much of the high-frequency content for which this trigger is most sensitive. Here are some ways to increase your chances for success: i) adjust the trigger sensitivity as high as possible, ii) place the trigger as close the site of the collision as possible, iii) hit the ball hard. If these don't work, it may be time for a sound trigger with a wider frequency response. Go here to find out how to make an extremely sensitive sound trigger from a tape recorder.|
1. An alternative to hitting the ball with a racket is simply is to throw the ball down on the floor. This is especially effective with a racquetball. The sound trigger is placed on the floor and can be moved to different positions to get different time delays. Before trying this, though, make sure that anything on the ceiling that the rebounding ball might hit isn't breakable. And when throwing the ball, be sure to be out of the way of the rebound.