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Flash sync speed and fast paced action..

MinCMinC Member
edited July 2012 in news & discussions
Hello I have a question regarding sports, and flash sync speed. to get the most out of my flashes on my canon 5d mark II I need to be at 1/200 or slower. Is it possible to freeze action if the subject is slightly lit by the ambient light. Let's say i underexpose the bakgorund, but my subject is still a bit lit. is it possible to work at 1/200 or will I get a semi blurred image with the flash freezing some of the action, and the ambient light on the subject is showing some motion? or should I just go with high speed sync, ? thanks!

Comments

  • in most cases 1/200 of a sec should knock out all the ambient. if u want to freeze motion with flash and the ambient is still being recorder at max sync speed (as u say) then lower ur iso and or stop down the lens this will effectivly eliminate the ambient light from affecting ur exposure and the only light exposing the subject will be ur flash, i do not advise hss.
  • I happen to have just done this yesterday, so I'll attach 2 full res files so you can see the result (exif data included). I fiddled with them a little in lightroom, but not too much, so you can still see essentially what you'll get with 1/200th shutter (I raised contrast to darken the background, but did no local-brushes). Check the sharpness of the ground and compare it to the blur of the airborne stuff.

    I've read that 1/4 flash power will give faster results for freezing action, but I had a 580ex and 430 exII both on full power due to the sun still being up. Please don't judge the artistry of the images too harshly as I'm still experimenting with this technique and my girlfriend said she would only help me for 5 minutes before going home without me.
  • nice pics! cool idea! did u take a test shot without flash to c how much the ambient is actually contributing to the subjects exposure
  • I had no time for testing, as we had to catch a train and my girlfriend refuses to run (she prefers to walk at normal pace, miss the train, then be mad at me).

    From past shoots I knew that the flash would overpower the background, but I didn't know by how much. If there had been a nice sunset I would have tried to integrate that, but it was cloudy anyway.
  • TrevTrev Moderator
    Yes, worked for stopping action. I saw by exif it was late in day and you had it at 400ISO which you could also drop to 100 ISO and open aperture by 2 stops which in turn would have meant you could drop flash power also.

    Slightly elevated flash heads next time to stop shadows crossing body if arms up in air would also make the image but as it was just a test and the 'girlfriend's abandonment' threats did not give you much time to experiment obviously.

    Good job.
  • Thanks Trev, I'll implement that advice the next chance I get. I am going to need a more patient assistant, or pick a focal point and run over to it while holding a radio trigger in my hand.
  • I'll have a chance to re-create the above experiment this weekend, but with more time and the help of some semi-cooperative drunks. My question is, given the profusion of debris in the air, how can I position my 2 flashes to reduce distracting shadows on the subject?
    If I want to give more dimensionality to the image, should I position a few flashes behind the subject, and flag them? Of course I need to rustle up more flashes.
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