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  1. #1
    jonraho is offline dPS Forum Member
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    Default Fast sync speed to freeze motion?

    HI Guys,

    Not sure if this has been covered

    I would like to figure out how i can go above my set 1/250th with my flashes to freeze motion.

    For example i have 2 bowens 500c facing my subject, the pulsar trigger and i want to capture ballet dance moves. however when i set the lighting and am at 1/250th at f/11 i get quite a bit of motion blur.. I'm using a Nikon D7000.

    I've done research and people say that at 1/60th or 1/200 should freeze the motion and used ND filters should help?!?

    Completely lost here haha. any pointers?
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  2. #2
    Rentham's Avatar
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    Default

    It's not motion blur from your shutter, per se. Your lights probably have a long flash duration. Most cheaper lights do. Also, the higher in power you go the longer the flash duration will be.

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    You can use the flash to freeze motion. you'll need to lower the ambient...
    Or you can do high speed sync with your studio strobes using a pocket wizard...or you can fool your camera into HHS with studio strobes using a flash that can do HSS.

    here's a link to a DPS post on the last option...
    http://digital-photography-school.co...ould-poop.html

    theres tons of articles on the pocket wizard route: "high speed sync with studio strobes"

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    Default

    The Bowens units are monolights, which don't do HSS. Speedlights will do HSS. +1 on the comment about flash duration.

    Your shutter cannot go faster than your sync speed when using a monolight. Well, it technically *can* go faster but you'll get black bands and the picture is unusable. So, you're limited to 1/250.

    To shorten the flash duration, reduce power on the head and either move the flash stands closer or increase your ISO.

    Or, use Speedlights with HSS compatible accessories, which means something like PocketWizards or an iTTL cable.
    Dave.

  5. #5
    sk66's Avatar
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    Could also just go to f/8 and reduce flash duration/output by almost 1/2.

    But Bruce is right. If the motion blur is due to motion being captured during the ambient exposure then reducing the flash duration, increasing ISO, larger f-stop, etc are all going to be the wrong choice. In fact, they could be the opposite of what needs to be done.

    The Bowens are rated at 1/900 T5 flash duration which means at max output it's equal to ~1/300 stopping power (T1 time). That could be enough for a lot of ballet, but it's not a lot.

    This is why you use speedlights for this kind of stuff. Not necessarily for HSS. Even the SB600 has 3x the stopping power at max output and x-sync.

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    The only other possibility is to get TTL-type triggers that can do "hypersync" with manual strobes. This is where the strobes are cranked up to increase the flash duration, so that the entire frame will be lit through a higher shutter speed. A sort of workaround for HSS with manual lights. However, as your Bowens are underpowered, this might not work (the tail-off of the pulse might be visible across the frame as an exposure gradient), and the compatibility of hypersync with triggers is often a great unknown until you test it out.
    I shoot with a Canon 5DmkII, 50D, and S90, and Pansonic G3. flickr stream and equipment list

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    One other hack you can do.

    Use a trigger with TTL pass through on the hotshoe (like the stratos or stratos II)

    Mount an FP speedlight on the hotshoe and enable auto FP in the camera menu. (You can turn the flash right down in power so it does not contribute to the exposure and face it backwards)

    Put your strobes on full power and fire with the remote trigger. You will need to control the strobe exposure either by distance to the subject or by aperture. It will steal about 3 stops of light, but I have fired regular strobes at 1/3000 using $100 triggers.

    This is not a portrait, but a test shot I did. No real composition and no PP etc. It does illustrate 1/2000 @ f4 with a single strobe, using the hack I outlined above.

    Last edited by scootermcq; 12-06-2012 at 06:27 PM.
    Scott
    Nikon D700, D300, 50mm 1.8, 85mm 1.8, 28-75 f2.8, 35-70 f2.8, 80-200 f2.8

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    jonraho is offline dPS Forum Member
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    Waaaaaa So much information! =D

    haha. First of all thank you all for the info.

    So basically the only way do it with the Bowen set up is by decreasing the power, increasing ISO and wider aperture? But that still will only get me to 1/300's ? Don't think the images will be sharp enough, but i'll give that a try.

    Right now only have SB700 would need to get another one with a snoot and grid and add the soft box to other XD

    Scott with the above mentioned : All i would basically need to do is place the flash unit on the hot shoe and fire as normal with the Bowens? But how can i sync them seeing that my hot shoe is taken up by the flash unit? Not sure if the the specific model has the "infrared" sync.

    Man i'm hopeless when it comes to this ahaha..

    Cheers
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    jonraho is offline dPS Forum Member
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    Quote Originally Posted by inkista View Post
    The only other possibility is to get TTL-type triggers that can do "hypersync" with manual strobes. This is where the strobes are cranked up to increase the flash duration, so that the entire frame will be lit through a higher shutter speed. A sort of workaround for HSS with manual lights. However, as your Bowens are underpowered, this might not work (the tail-off of the pulse might be visible across the frame as an exposure gradient), and the compatibility of hypersync with triggers is often a great unknown until you test it out.
    Thanks for this, dont think current triggers have TTL will have to read on it, but what about using pocket wizards?
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    Quote Originally Posted by jonraho View Post
    So basically the only way do it with the Bowen set up is by decreasing the power, increasing ISO and wider aperture? But that still will only get me to 1/300's ?
    Not exactly. Without reducing the power your max freezing capability is 1/300. By reducing the flash power you are increasing the freezing power by reducing the duration time. I.e 1/2 power gets you 1/600th (it doesn't actually work that simply). You have to increase ISO/aperture in order for the reduced flash output to be enough for proper flash exposure.

    The problem is that this will also increase your ambient exposure. And since you are already at x-sync there's not really anything to be done about it with out going into HSS/tricks.

    If you can compensate by moving the lights closer instead of ISO/Aperture adjustments then it won't affect the ambient exposure...(but the dancers will probably be smashing into them).


    The intent of using the flash w/ the bowens is not to use the flash for illumination, but to trick the camera into HSS mode. I don't think mixing flash output w/ the strobes for illumination will really help in this situation.
    Last edited by sk66; 12-08-2012 at 03:38 PM.

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