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  1. #1

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    Need help making a special light source from strobes

    I'm in the process of trying to make a specific light source with one of my strobes. I need a light that produces a thin wide band of light for lighting a model. So - I took one of my strobes, put a cardboard tube on it about 2 feet long with a cover on the end with a very narrow slit in it expecting to get a narrow band of light.

    Instead, when I fired the flash, I got a perfect reversed image of the flash tube in my strobe! Duh, it took a while for it to finally sink in that all I had created was a version of a pinhole camera.

    So - any ideas on how to pull this off. The light source can as close as about 3' away from the model and the light band needs to be about 1" tall by about 12" wide.

    A simple version is the sun shining through the blinds on a window, but that won't work with the studio type of set up that I have.
    Dan's website: www.dandozer.com

  2. #2

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    IIRC I saw something like this done with hot lights in a EK newsletter. The photographer used two large barn doors positioned somewhat
    like this. / \ actually the doors
    were slipped / a little bit.
    \



    Francis in VT
    Last edited by Francis in VT; 06-01-2010 at 01:32 PM. Click to view previous post history. Reason: trying to get the doors/\ right

  3. #3
    Mainecoonmaniac's Avatar
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    If you want your band of light to have a sharp line, why don't you try using some grip equipment and use flags? There are long flags called cutters made by Mathews. You'll have to use gobo arms and some C stands with them. The further the cutter it is from the light source, the sharper the shadow's edge. Also I would use a point source of light for sharp shadows.

    Here's a link: http://www.msegrip.com/mse.php?show=...ducts_ID=26038

  4. #4
    patrickjames's Avatar
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    If you want the edges to be sharp you are going to need some version of a fresnel to focus the light in a beam. Then you can use barn doors/cutters or whatever else your heart desires to trim the light. If you don't have that, your only other option is to move the strobe back quite a ways and then cutters or foamcore could work for you. You will get a lot of spill around the cutters though. Barn doors by themselves are good for a general cut, but you won't get a sharp edge with strobes. Remember the importance of the relationship between the size of the light and the distance from the subject. The farther away the light is the sharper the edges of the shadows will be. Think about the sun for example.

    You didn't mention what kind of strobes you have.
    Last edited by patrickjames; 06-01-2010 at 02:45 PM. Click to view previous post history.

  5. #5

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    Thanks for the advice guys. This "project" is going to have to be "do it yourself" so buying something like cutters is not in the picture.

    Patrick - what you describe makes sense and I think I might be able to put something together that might work. I think the challenge will be getting a light source that will be strong enough to cast enough light on the model. Might require a trip to Home Depot to see what kind of shop lights they might have (buying something from Home Depot is always justified). The other challenge will be sheilding the model from any potential spill over light. BTW = my strobes are 500 watt units that I normally use with soft boxes as lighting.

    Thanks again.

    Dan
    Dan's website: www.dandozer.com

  6. #6
    Mike Wilde's Avatar
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    Consider looking into fitting a flash tube into an elipsoidal theatrical spot luminaire; some are made with fixed focal length optics and some have zoom optics.

    These fixtures have an adjustment for sharp/unsharp focus, and have shutters placed at the gate, where the lens focuses, so sharp cuts of the light output are possible.

    The challenge is that they are made for long throws. Optics in fixed units tend towards 50, 38, 25 and 19 dgerees in one line I am familiar with.

    You may not need to go with a flash tube; these luminaires are typically fitted with a 500 or 1000w lamp, and so may only need to be colour balanced if there are other daylight balanced light sources in your set. Otheriwse colour correct for tungsten on the camera, and start shooting

    Shoot quickly, for they are most certainly 'hot' lights, although the more modern designs have a dichroic reflector and some (selecon out of new zealand) have a large dichroic mirror that makes the beam free of IR enough that you can even use acetate gobos to put patterns into the gate and project them. Most old style lamps of this sort use a spring steel gobo that glows red hot while the lamp is operating.
    my real name, imagine that.

  7. #7
    patrickjames's Avatar
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    Don, a shop light from Home Depot isn't going to help you here. If you don't have a budget, my recommendation for you is to pickup two sheets of foamcore at a local artstore. Hopefully you have one near you. I would go with the largest size they have, and get one with at least one black side. The cost will be minimal. If you move the strobe back at least 10' (remember, the farther the better) you should be able to get the result you are trying to achieve. Might not be perfect, but I think it will work for you.



 

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