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Thread: Sync speed

  1. #1
    Ralph Thompsonr's Avatar
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    Sync speed

    I am planning some studio work with my Cambo Legend with 150mm, n0.0 and 210mm n1 copal shutters. I have modern Profoto 600 watt sec. monolights.

    I've read that the light is reduced by about half between 1/100th sec and 1/500th sec with a the max. shutter speed that can be used without cutting off any light please?
    Is there a recommended shutter speed with electronic flash?

  2. #2
    Whatever David A. Goldfarb's Avatar
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    Re: Sync speed

    Quote Originally Posted by Thompsonr View Post
    I've read that the light is reduced by about half between 1/100th sec and 1/500th sec
    This would only be true in very limited circumstances, with very powerful strobes that might have a flash duration of around 1/300 sec. at maximum output. I don't think your Profoto lights fit that description. Run some tests to be sure, but with leaf shutters you should be able to sync at any speed.

  3. #3
    Darkcloth Fumbler
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    Re: Sync speed

    the actual speed of a strobe is usually between 1/1000 and 1/10,000 second. so you ought not to have any problem at even 1/500. if your flash pops are unusually long, they're still going to be much faster than 1/100.

    pick a shutter speed that is fast enough to eliminate any ambient light - unless you want some ambient in it. and slow enough to capture the entire flash duration.

    i've never heard of the strobe light being cut in half between 1/100 and 1/500. where'd you read that?

    later: a quick google shows that the maximum duration of the flash pop for a 600 is 1/850 second. so you ought to be fine at 1/500 shutter speed, but you can play it safe and pick 1/250 if you want.

    also, when you dial down a strobe's power, you're essentially cutting the duration as well. if you fire at 1/2 power, you'll have even less to worry about.
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  4. #4

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    Re: Sync speed

    With an iris shutter, which has to open completly before it closes, shutter speed is irrelevant in terms of how much flash it lets in as the flash is faster than the shutter speed and the pc socket on the shutter makes sure the flash fires at the correct time.

    The shutter speed will, however, determine how much available light from the room hits the film as does the f-stop.

    steve simmons

  5. #5
    Ralph Thompsonr's Avatar
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    Re: Sync speed

    Great thanks guys,
    With the cost of film and processing, you've saved me a few dollars in experiments.
    Now I feel confident to shot at 1/250th without any concerns
    Many thanks
    Ralph

  6. #6

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    Re: Sync speed

    Question for someone really familiar with LF shutters and electronic flash. When exactly does the electronic flash start to fire? I assume it is some fraction of a second after the shutter is fully open otherwise the film would not initially get the full dose of light from the flash. Is this the case with all modern shutters and what typically is the time delay between shutter full open and flash startup. Just curious about the details.

    Nate Potter

  7. #7

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    Re: Sync speed

    It will fire just as the shutter reaches a fully open position. Electronic flash has a very quick 'burn' and there does not need to be a delay between the shutter being fully open and the flash firing as there needed to be in the old days with flash bulbs.

    steve simmons

    steve simmons

  8. #8
    Whatever David A. Goldfarb's Avatar
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    Re: Sync speed

    It's also not as if there is some timed delay in the shutter on X-sync (which is the only option on modern shutters--older ones might have had M for flashbulbs, or a variable delay on Ilex shutters for different types of bulbs). It's just a simple switch that closes mechanically when the shutter is fully open.

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