2nd curtain question

Discussion in 'Photography Beginners' Forum' started by tjones8611, Jan 1, 2010.

  1. tjones8611

    tjones8611 TPF Noob!

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    When do you use 2nd curtain? Ive seen examples, but have not been able to locate the best uses of 2nd curtain strobing.
     
  2. gsgary

    gsgary Been spending a lot of time on here!

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  3. Chris of Arabia

    Chris of Arabia Herding cats since 1988... Supporting Member

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    You'd usually use it when photographing a moving object with a long shutter duration - for arguments sake, lets say 1/4 sec or greater.

    When the flash is synced to the first curtain, you will end up with movement lines in front of the moving object. When synced to the second curtain, those movement lines trail out behind it, making the object look like its in motion, rather than the flash just freezing the action as if it were stationary.
     
  4. JimKing

    JimKing TPF Noob!

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    Chris of Arabia has given the correct answer. If the use of the word curtain is confusing you can just think of it this way. First remember the flash only lasts a very short time let's say 1000th of a second and as Chris mentioned the whole exposure is maybe 1/4th of a second or 250 times as long as the flash. If the flash goes off as soon as the exposure starts (first curtain) then the motion blur will be after the flash which will, with a moving object, make the blur continue in the direction of movement or forward from the flash exposure. Now if the shutter opens and stays open for almost the whole exposure (creating a blur) then just before the shutter closes the flash goes off (second curtain) you will now have a sharp flash exposure at the front of the blur instead of the back. Did I make it clearer or just muddy the waters.
     
  5. tjones8611

    tjones8611 TPF Noob!

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    Got it, thanks! So much simpler than what I have read elsewhere, however Im sure its not so easy to do. I would imagine several shots are required to get the perfect one.
     
  6. KmH

    KmH Helping photographers learn to fish Supporting Member

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    For the majority of your flash work you'll want to use rear/second curtain sync.
     
  7. Dwig

    Dwig TPF Noob!

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    Anytime you take a flash picture with an electronic flash the shutter will be open much longer than the flash illumination lasts. There will always be some ambient light exposure unless there is absolutely no ambient light (total darkness).

    Any moving object that is bright enough can leave a ambient lit image and, if moving fast enough, that image will be blurred. The higher the shutter speed (up to the camera's maximum sync speed, of course) the shorter the blur and the dimmer the blur. While its often undetectable, this blur can be visible at even the highest sync speeds if the object is bright enough and moving fast enough (e.g. a car's headlights).

    If you use the normal first curtain sync, the flash fires when the first shutter curtain (with modern shutters its the first "blade set" actually) barely gets completely open. Any ambient blur occurs after the flash exposure. If you use "second curtain sync" the flash is triggered just before the second curtain starts to close. Any ambient blur occurs before the flash exposure. As a result in a situation like a moving car, the blurred ambient exposure of the car's lights would appear in front of the car with normal sync and behind it with second curtain sync. The latter leaves a more "normal" appearing image.
     

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