This chapter is from the book
This chapter is from the book
This chapter is from the book
Fun with Multiple Flash Exposure
Flash units have limited power and range. We’ve all seen those special moments at sporting events when hundreds of flashes are going off. None of them will reach the player on the field, and few will go beyond ten feet, but when they do, the area of coverage will be fairly narrow. That works well in most situations but not when you need to cover a wide area. Sometimes you can remedy the problem by using multiple flash units; other times you can use long exposure and manually pop the flash in different parts of the scene. And if you use multiple flash pops, some flash units will fire several in succession to freeze the subject in multiple phases of motion in the same scene.
Repeating Flash in the Same Exposure
Some of the more advanced flash units enable you to create a stroboscopic effect by firing off the flash multiple times within a single exposure, allowing you to capture the subject in various stages of motion (Figure 4.18). Here’s how it works: You determine the number of flashes and the duration between each burst (which range from 1 Hz to 50 Hz or more), as well as the strength of illumination.
)
Figure 4.18 This diving scene was captured in three stages by setting the flash at ¼ power at 3 Hz, producing three flash bursts that went off in succession during a one-second exposure.
Canon EOS-1 • ISO 200 • 1 sec. • f/5.6 • Canon 20–35mm lens at 20mm • Canon Speedlite 430EZ Flash
The following tips can help you repeat the flash in the same exposure:
- Determine when the subject will begin and end the action: This technique generally fails because multiple flash pops occur when the subject is passing through its own motion. So try to figure out where the subject’s motion begins and ends, and how long it will take to get there. Doing so will lead to an effective multiple flash image.
- Compose the subject so flash doesn’t overlap: Exposure level increases each time the flash is exposed on the same subject, so if not done evenly, part of the scene will receive more exposure.
- Use a long exposure: Make the exposure long enough to capture the subject’s action from start to finish. For example, if the routine takes two seconds, make sure the exposure is that long.
- Limit power: You don’t always need a lot of power to expose a scene, especially when you use flash units that have lots of power and fast recycling times. Turning the flash unit down to ½ or ¼ power allows you to recycle fast enough for situations that require multiple bursts.
- Be conservative: Use the minimum number of flash pops to avoid some of the problems that would occur due to overlapping. A good measure is to use three flash pops. Sometimes, too many pops of flash create distractions in the image.
Manually Popping Flash
When you take the flash off the camera, place the camera on a tripod, and set the camera on a long exposure, you can then walk though the scene and manually fire off bursts of light in all the desired places. This technique works great in wide, dimly lit areas, as well as for a few creative applications (Figure 4.19).
)
Figure 4.19 Although these might look like real ghosts, one person wearing a sheet was manually illuminated by a burst of flash every couple of steps. Because the image was shot as a long exposure in a relatively dark area, the ambient portion of the scene did not affect the burst.
Canon 20D • ISO 100 • 30 sec. • f/8 • Canon 20–35mm lens at 20mm (equivalent to 32mm) • Canon Speedlite 580EX Flash
