Canon EOS 50 E - Page 62

Part 2: Technical Information
The E-TIL Flash System's major features backing the above points are as follows:
1. Improved AIM System: Unlike TIL off-the-film auto-flash metering, the six-zone
metering sensor is fully utilized and linked to the focusing points. This enables more
intricate flash output control for the subject.
2. Flash metering sensor unnecessary: Since the 1TL evaluative flash metering system
does not use off-the-film metering, it is not affected by differences in surface
reflectance of different films. Flash metering is therefore more precise.
3. Better control: Since the flash output can be precalculated and retained, the proper
flash exposure can always be obtained regardless of the camera-to-subject distance.
4. Fast shutter sync speed (FP flash): Since the flash output can be precalculated and
retained, a normal flash duration is set for a sync speed of 1/125 sec. (X-sync) or
slower. If the shutter speed is faster than the X-sync speed, the flash mode switches
automatically to a high sync speed (FP flash). This enables the flash to synchronize
automatically with all shutter speeds.
5. FE lock: Like the AE lock used with partial metering, the FE (flash exposure) lock
feature locks the flash exposure reading obtained by the preflash reflecting off the
subject. It enables sophisticated flash techniques.
Flash control with other EOS cameras is the same as before:
• With the built-in flash: Off-the-film metering with 3-zone TIL auto flash control
linked to the focusing points.
• With an EZ-series Speedlite (540EZ, 430EZ, etc.): Off-the-film metering with 3-zone
A-TIL auto flash control linked to the focusing points. The same effects are obtained
as with the EOS A2/A2E and other cameras having multiple focusing points.
• With the ML-3 and other multiple flash unit systems: As with the built-in flash, 3-
zone TIL auto flash control linked to the focusing points is used.
1) Basic Operation of E-TTL Auto Flash Exposure System
1. When the shutter button is pressed halfway:
a. The EOS camera determines the flash aperture and shutter speed.
b. The ambient light distribution is metered by the 6-zone metering sensor which is
used to calculate the output of the main flash.
2. When the shutter button is pressed completely, the picture is taken with E-TIL Auto
Flash Exposure Control based on the flash aperture set in step 1 above.
a. Before the mirror flips up, the 6-zone metering sensor meters the ambient light
instantaneously immediately before the preflash fires.
b. Before the mirror flips up, the preflash fires and the reflected light is metered by
the 6-zone metering sensor.
• In steps 2-1 and 2-2, the light reflected off the subject from only the preflash is
metered.
• The ambient light distribution metered in 1-2 and the reflection of the preflash
metered in 2-2 are used to calculate the main flash output which is then locked.
c. The main flash is fired according to the calculated and locked output.
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