State-of-the-Art Technology Fusing Light and Personal Expression What you see is what you get with E-TTL autoflash and a multi-zone metering sensor. E-TTL autoflash Speedlites broaden possibilities with natural-looking flash lighting. The E-TTL (Evaluative TTL) autoflash system uses the EOS camera's multi-zone metering sensor to control the flash output. The multi-zone metering sensor is linked to the camera's multiple focusing points so that the metering is weighted at the point where focus is achieved (where the main subject is assumed to be). The existing light level is also metered to enhance exposure accuracy. With multiple metering zones, the flash exposure is very precise. The EX Speedlite first fires a preflash whose reflected light is metered by the multi-zone evaluative metering sensor along with the existing light. The correct flash output is then calculated and stored in memory. Starting from the instant the shutter button is pressed, the E-TTL autoflash system works as shown in the sequence chart below. The optimum flash output is calculated so that the exposure is well balanced between the existing or natural light and the flash illuminating the subject. As with a normal exposure without flash, the flash exposure is centered on the subject (where focus is achieved). Bright or reflective objects in the background are also detected and the exposure is controlled accordingly. E-TTL autoflash system operation flow 1. Shutter button pressed halfway Autofocusing and evaluative metering (with the multi-zone sensor linked to the focusing point) are executed simultaneously. The existing light is thereby metered. 2. Shutter button pressed completely A preflash is fired, and the reflected light is metered by the multi-zone evaluative metering sensor. 3. The meter readings of the existing light and preflash are compared and the main flash's output is calculated and stored in memory. 4. The reflex mirror goes up, the first shutter curtain sarts to open, the main flash fires, the film is exposed, the second shutter curtain closes, and the reflex mirror goes back down. 5. The flash exposure confirmation lamp lights. Advanced Speedlite features are fully automatic The E-TTL autoflash system calculates and stores the flash output before firing the main flash. Besides functioning as the main light, the Speedlite can also be used as supplemental light in a variety of ways. In low light, automatic slow-speed sync exposes both the subject and background correctly (with Aperture-priority AE). For fill flash in daylight, high-speed sync (FP flash) is effective. With FE lock, you can lock the flash exposure for the subject and change the framing while retaining the correct flash exposure. And when the EOS-3 is combined with the Speedlite 550EX, E-TTL wireless autoflash enables a flash ratio to be set with two slave groups consisting of multiple Speedlite 550EXs. The 550EX also features flash exposure bracketing (FEB) which brackets the flash exposure automatically. All these advanced techniques are now easier than ever before, with a natural-light Speedlite like never before. E-TTL autoflash extends the boundaries of flash photography. 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. Up to three slave groups (consisting of any number of Speedlites) can be controlled. A slave group consisting of multiple Speedlite 550EXs can also be used as one giant Speedlite. In this case, the flash duration willbe 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. The figure (on the left) shows a multiple-Speedlite set-up centering on the EOS-3 mounted with the master Speedlite 550EX (flash is turned off). 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 forno (wood-burning oven) in the background, and the restaurant's atmosphere come across well in the picture on the right. << Back to Main . 1 . 2 . 3 . 4 . 5 . 6 . 7 . 8 .