Stroboscopic (Multi) flash

This special-effect feature of the 430EX and 580EX II allows you to fire a series of flashes from a single Speedlite during one exposure — for example, showing a subject moving within a single photograph (see 8-16).

In this image, the model moved her head throughout the two-second duration of the photo, which was taken outside on a dark night The flash was pointed directly at her, and it took a couple of tries to get her to move her head at about the right pace for the three shots. Using a bounce flash or diffusing device on the flash could help eliminate some areas being more exposed than others and make the exposure more even. Taken with a 1D Mark IIn using an EF 24-70mm f/2.8L lens at ISO 50, 2 seconds, f/5.6.

To use the stroboscopic function, you need to decide what kind of a photo you want to take — how many images of your subject you want in your photo, and the composition. So, if you know that you want eight images of your subject in the photo, this means your flash needs to fire eight times for one exposure. Consider the following formula when trying to determine how to set your Speedlite and camera:

Number of flashes/firing frequency = shutter speed

So, if you’re shooting eight flashes and the frequency is four per second, you need a shutter speed of two seconds (8 / 4 = 2).

In the Canon Instruction Manual for the Speedlite 430EX and 580EX II, there is a chart for maximum stroboscopic flashes that you will need to set your flash. Expressed in hertz (Hz), the firing frequency number or number of flashes per second ranges up to nine.

Depending on the flash output you select, you can reference a corresponding number on the chart in the manual that you must enter into the flash.

The most effective images taken using the multi-flash feature are those where the subject is quite reflective, against a contrasting, dark background.

And, while you can technically set your camera to a long setting or even Bulb and set the flash to keep firing indefinitely, this can cause the flash to overheat. Note that you don’t want to fire the flash more than ten times in succession because the flash contains an automatic mechanism that causes it to shut down to protect itself if it becomes too hot. If it shuts down, you must let it rest for at least 15 minutes before attempting to use it again.


NOTE

You cannot set the flash to full power in Stroboscopic (Multi) mode, or even to half power; the power output option begins at 1/4.

Category: Flashes

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