| For these kinds of flashes, the duration of the flash is based on the power setting. At lower power settings (1/2, 1/4, etc) the flash is just as bright, it just stays lit for a shorter time. The power specs for both flashes are similar. The Canon is slightly more powerful, but the Vivitar has a slightly shorter flash duration at full power. That said, the Canon can go down to 1/128 power, while the Vivitar only goes to 1/16. With my various Nikon speedlights, which have similar specs, I found I needed to use 1/32 power (about 1/10,000 second) to freeze a hummingbird (and multiple flashes to get enough light), so the Vivitar wouldn't work for me. For practically anything slower though, the Vivitar would work fine. |
