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Question of the Day: Which is the most hair-raising South African mountain pass you've driven?
1st / 2nd curtain flash / shutter
- Thread starter Dolby
- Start date
With ettl there are always two flashes. A preflash followed by the flash. Normally they happen so quickly they appear to be one flash. What's happening is there's a preflash, the shutter opens, the flash fires and then the shutter closes. Because you're using second curtain the second flash is at the end of the exposure.
Dolby
Honorary Master
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Ahhh - so it is the preflash I'm seeing then.
I purposely put shutter at 5 seconds to see exactly how curtains worked and expected to see only one flash at the start OR one at the end.
Didn't know there was a pre. Thanks!
I purposely put shutter at 5 seconds to see exactly how curtains worked and expected to see only one flash at the start OR one at the end.
Didn't know there was a pre. Thanks!
CaffeinePirate
Well-Known Member
Isn't it to help with lighting/ exposure etc?
CaffeinePirate
Well-Known Member
Exposure Options
Canon’s E-TTL II (Evaluative-Through-The-Lens) exposure system works by triggering a low power preflash that the camera measures to determine the actual exposure. If you have an E-TTL II-compatible camera (and if it was introduced after 2004, it probably is) the camera will adjust the flash duration based on the amount of preflash light reflected back from your subject and, if available, the focusing distance the lens is set to. The distance information provides more accurate results than reflected readings alone. Furthermore, with E-TTL II cameras, flash metering is no longer linked to the AF point you’re using — this reduces exposure errors if you prefer to lock focus and re-compose.
E-TTL and the current E-TTL II flash metering systems require a Canon EX-series Speedlite, as well as a compatible Canon EOS camera body. Several compact Canon PowerShot digital cameras, such as the popular G-series models, also can accept and work with EX-series Speedlites.
If you’re using one of the older Canon EOS film bodies, a modern EX-series Speedlite defaults to standard TTL flash metering, where there is no preflash and camera adjusts the flash duration in real-time. The flash unit’s instruction book refers to these as “Type B” cameras. Type B cameras include older film SLRs such as the original EOS-1, EOS-1N, EOS A2/A2E, and similar models from the early 1990s or before.
Considering that E-TTL II is completely automated, it works surprisingly well. It’s not infallible, though. When the lighting is tricky or your subject is brighter or darker than average, you’ll have to apply some human intelligence to get the best possible exposure.
http://learn.usa.canon.com/resources/articles/2011/speedlite_tip_pt2_article.shtml
Canon’s E-TTL II (Evaluative-Through-The-Lens) exposure system works by triggering a low power preflash that the camera measures to determine the actual exposure. If you have an E-TTL II-compatible camera (and if it was introduced after 2004, it probably is) the camera will adjust the flash duration based on the amount of preflash light reflected back from your subject and, if available, the focusing distance the lens is set to. The distance information provides more accurate results than reflected readings alone. Furthermore, with E-TTL II cameras, flash metering is no longer linked to the AF point you’re using — this reduces exposure errors if you prefer to lock focus and re-compose.
E-TTL and the current E-TTL II flash metering systems require a Canon EX-series Speedlite, as well as a compatible Canon EOS camera body. Several compact Canon PowerShot digital cameras, such as the popular G-series models, also can accept and work with EX-series Speedlites.
If you’re using one of the older Canon EOS film bodies, a modern EX-series Speedlite defaults to standard TTL flash metering, where there is no preflash and camera adjusts the flash duration in real-time. The flash unit’s instruction book refers to these as “Type B” cameras. Type B cameras include older film SLRs such as the original EOS-1, EOS-1N, EOS A2/A2E, and similar models from the early 1990s or before.
Considering that E-TTL II is completely automated, it works surprisingly well. It’s not infallible, though. When the lighting is tricky or your subject is brighter or darker than average, you’ll have to apply some human intelligence to get the best possible exposure.
http://learn.usa.canon.com/resources/articles/2011/speedlite_tip_pt2_article.shtml