Speedlite Transmitter ST-E2 Instead of using a Speedlite 550EX as the on-camera master unit, this wireless transmitter can be used. This unit can control up to two groups of slave units with ratio control between each group. The Wireless Autoflash can be used for creative lighting effects in a number of ways. In this page are examples of how the EOS-3's Wireless flash system was used: For the photos of the model car, simply firing shot the first photo from the main Speedlite 550EX that was attached to the camera. No fill flash from a second 550EX was used. The second photo on the model car, a fill flash was used, this time coming from a second 550EX placed on a 45° direction from the left side of the camera. Main flash was fired from the camera. Both 550EXs were fired off using the E-TTL flash without any flash ratio adjustments. Using the Spider-Man figurine (pix at the bottom), the main 550EX has been removed from the camera and the Transmitter ST-E2 has been attached to the EOS-3 as the Wireless flash controller for the two 550EX Speedlites. The first photo was shot with the main 550EX placed at 45idirection from the left side of the camera while the fill-in flash from the second 550EX was placed at a 90i side lighting direction from the left side of the figurine and set in 1:2 ratio. The second photo, the 550EX on the left side of the camera was switched off and the second unit was fired off from its original 90° side lighting direction. This has resulted in a strong illumination that reflects the texture of the figurine. << Back to Main . 1 . 2 . 3 . 4 .