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E-TTL : Flash wireless
Il Maniero Restaurant, Castelmola, 14h [EF 50mm f/1,4 USM, 1/6s at f/5,6]
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E-TTL wireless autoflash for custom lighting effects.
With multiple Speedlite 550EXs, wireless flash photography is fully automatic. The basic flash operation is the same as with a single Speedlite 550EX. The preflash reflected off the subject is metered and the optimum flash output is calculated and stored in memory. These data are then transmitted by the on-camera, master Speedlite 550EX (or Speedlite Transmitter ST-E2) via high-speed, wireless pulse signals. The Speedlite 550EX slave units then fire the flash accordingly. A slave group consisting of multiple Speedlite 550EXs can also be used as one giant Speedlite. |
In this case, the flash duration will be short since the flash output of each Speedlite in the slave group will be low. Thus, it will be possible to capture extremely fast action such as the splash of a milk drop. Also, a modeling flash can be fired so you can see the flash lighting effects before taking the picture. The flash exposure of all the slave units can be checked with the flash exposure confirmation lamp of master Speedlite 550EX or ST-E2.
Setting a flash ratio with slave groups on the master unit.
A flash ratio for two slave groups (A and B) can be set with the master Speedlite 550EX (or Speedlite Transmitter ST-E2). The A:B flash ratio can be set from 8:1 to 1:1 or from 1:1 to 1:8 for a total of 13 steps in 1/2-stop increments. Each slave group fires a flash based on the flash ratio which is controlled to obtain a correct flash exposure. Slave group C operates independently from groups A and B. It can be set by the master Speedlite 550EX for flash exposure compensation up to ±3 stops in 1/2-stop increments. It is useful as a background or accent light for studio portraits. Speedlite Transmitter ST-E2 can control only slave groups A and B.
No experience and expertise is necessary for using multiple Speedlites.
The figure above shows a multiple-Speedlite set-up centering on the EOS-3 mounted with the master Speedlite 550EX (flash is turned off). |
E-TTL Wireless Autoflash Exposure Sequence Chart
Ratio setting are only supported by the EOS-1V and the EOS-3 |
| Slave A serves as the main light pointed directly at the subject. Slave B faces the wall on the right to bounce the flash for a soft lighting effect. In addition, slave C is placed right behind the subject to give a halo effect. Based on this set-up, the pictures were taken while the flash ratio was modified. The two culinary artists, the fomo (wood-burning oven) in the background, and the restaurant's atmosphere came across well in the picture. |
Part of Canon "Flash Work" / E-Version © by Daniel ROCHA
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