Otherwise known as the Evaluative Through the Lens System, the E-TTL system was introduced in 1995 with the debut of the Canon Elan II/50 Camera. Even if the metering process is still done through the lens of the Camera, the E-TTL system is a more advanced system and operates on dissimilar system to that of the TTL system. In addition, the E-TTL system is not backward compatible. The E-TTL system functions by firing a pre-flash, whose brightness is known, from the flash unit to ascertain the exact level of flash exposure. This is achieved by measuring the pre-flash light which is reflected off from the scene. The camera then calculate the correct flash pulse to get a mid tone level on the subject.
As mentioned earlier, the E=TTL system is more advance than that of the TTL or A-TTL system because of its algorithms. With better algorithm programming, the system is fill flash daylight pictures more efficiently. Apart from this, the E-TTL system is coupled to the auto focus point and this result in better and finer grained pictures than even those multi points TTL flash systems. Currently all late modeled Canon EOS film cameras support the E-TTL system. The digital range of camera adopted the E-TTL system after the Canon D30 was introduced. How the order of operation of the E-TTL system is as listed below:
Once the shutter button is depressed halfway the ambient light metering process runs it normal course of operation. Aperture size and Shutter speed are programmed by the user or camera depending on which mode the camera is operating under. After the shutter button is press down all the way, the camera fires a pre-flash from the flash unit. The light which is reflected of the scene is then measured by the metering system to ascertain the right power output for the actual flash pulse to get the correct exposure level.
If you are taking pictures under bright lighting conditions, the camera auto filled reduction feature will operate to reduce the flash intensity from ranges between 0.5 to 2 stops. The internal mirror then flips up to expose the film or sensor during the shutter run. After the shutter closes, the mirror will flip back down. If the camera has such a feature as a warning light for confirming the flash exposure operation, then it will start to glow.
The problem with the E-TTL system is that, the pre-flash will result in those who blink quickly to be snapped while in mid blink resulting in "droopy eyes" looks. The situation gets more problematic when you use a slow shutter speed and the second curtain sync together. To overcome this problem, just wait a short while before firing off the main flash burst. Remember to forewarn the subjects as they might think the actual photo has been taken after you fired the pre-flash. - 15437
As mentioned earlier, the E=TTL system is more advance than that of the TTL or A-TTL system because of its algorithms. With better algorithm programming, the system is fill flash daylight pictures more efficiently. Apart from this, the E-TTL system is coupled to the auto focus point and this result in better and finer grained pictures than even those multi points TTL flash systems. Currently all late modeled Canon EOS film cameras support the E-TTL system. The digital range of camera adopted the E-TTL system after the Canon D30 was introduced. How the order of operation of the E-TTL system is as listed below:
Once the shutter button is depressed halfway the ambient light metering process runs it normal course of operation. Aperture size and Shutter speed are programmed by the user or camera depending on which mode the camera is operating under. After the shutter button is press down all the way, the camera fires a pre-flash from the flash unit. The light which is reflected of the scene is then measured by the metering system to ascertain the right power output for the actual flash pulse to get the correct exposure level.
If you are taking pictures under bright lighting conditions, the camera auto filled reduction feature will operate to reduce the flash intensity from ranges between 0.5 to 2 stops. The internal mirror then flips up to expose the film or sensor during the shutter run. After the shutter closes, the mirror will flip back down. If the camera has such a feature as a warning light for confirming the flash exposure operation, then it will start to glow.
The problem with the E-TTL system is that, the pre-flash will result in those who blink quickly to be snapped while in mid blink resulting in "droopy eyes" looks. The situation gets more problematic when you use a slow shutter speed and the second curtain sync together. To overcome this problem, just wait a short while before firing off the main flash burst. Remember to forewarn the subjects as they might think the actual photo has been taken after you fired the pre-flash. - 15437
About the Author:
Tim Harris is a canon camera enthusiast. For tips on choosing and buying cameras, do check out Canon OS Camera website. Camera 40D Digital Rebel XTI 3D Blog
