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Thread: Flash & Custom WB Test.

  1. #1
    Super Duper
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    Flash & Custom WB Test.

    I just went through an exercise to get proper color when shooting simple work with speed-lights. In particular, when using the technique of "dragging the shutter" to open up backgrounds while using TTL flash in low light ... which involves a color temp mix that results in too much post work and possible file degradation.

    I used the Leica S2 for these tests, with an ISO of 640 in fairly dark or very dark ambient conditions that were lit by tungsten bulbs or lamps. The lens was the S70mm. Many DSLR users can move the ISO up to 800 or even 1600, which increases the problem even more.

    These comparison shots are not color corrected ... color temps are straight from the camera, converted to jpgs and attached here.

    I used a Graslon Prodigy Dome diffuser which has interchangeable white and amber domes.

    In the tri-panel image with Exif info below, a manual shutter speed of 1/30 @ f/2.5 was used to open up the backgrounds (dragging the shutter). When doing this, the ambient color temp exerts a more dominate role in the over-all image.

    When AWB was used with the white diffused flash, the images goes quite warm.

    Then, when a custom WB was employed with the white diffused flash, the situation improves, but still exhibits a warm cast.

    When a custom WB is used with the amber diffused flash the colors are then true. A slight exposure tweak would render the scene as it really was.

    This was demonstrated even more dramatically when the tungsten source was a bit more isolated as in the bed-side lamp shot ... Custom WB set off pillow, walls are blue.

    -Marc
    Last edited by fotografz; 13th May 2012 at 03:01.

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    Re: Flash & Custom WB Test.

    Great report of your exercise. Thank you.

  3. #3
    Shelby Lewis
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    Re: Flash & Custom WB Test.

    Thanks Marc... I hadn't seen these diffusers before. Mighty big, but seemingly well designed. I might have to try one out. I love how "clean" the color looks with the amber dome in use alongside those (seemingly) tungsten bulbs.

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    Re: Flash & Custom WB Test.

    Quote Originally Posted by Shelby Lewis View Post
    Thanks Marc... I hadn't seen these diffusers before. Mighty big, but seemingly well designed. I might have to try one out. I love how "clean" the color looks with the amber dome in use alongside those (seemingly) tungsten bulbs.
    Hi Shelby,

    Yeah, they are biggish, but the bigger the light source the better. The dome cover works best for more dispersion in areas where there are bounce surfaces.

    Graslon makes two sizes, the one shown is the Prodigy, and the smaller one I use on a 35mm DSLR is called the Insight ... which fits in a camera bag a bit easier.

    -Marc

  5. #5
    fotofreak
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    Re: Flash & Custom WB Test.

    Thanks man for that insight!

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    Re: Flash & Custom WB Test.

    Quote Originally Posted by fotografz View Post
    Yeah, they are biggish, but the bigger the light source the better.
    The Graslons are much more than just bigger diffusers. To the best of my knowledge, they're the only speedlight diffusers that employ a counter reflector and an intermediate lens behind the convex diffuser.

    Compared to your grandfather's Stoffen, or the Fong abomination, well, there is no comparison.

    They really do mimic a well designed softbox.

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    Re: Flash & Custom WB Test.

    Quote Originally Posted by Kirk Candlish View Post
    The Graslons are much more than just bigger diffusers. To the best of my knowledge, they're the only speedlight diffusers that employ a counter reflector and an intermediate lens behind the convex diffuser.

    Compared to your grandfather's Stoffen, or the Fong abomination, well, there is no comparison.

    They really do mimic a well designed softbox.
    That's right Kirk, the interior design as you mentioned serves to put out an even spread of light across the surface of the larger diffuser face. I measured only a 2 to 3 % fall-off at the very edges.

    The other innovation is the mount system ... which is one size fits all, and is pretty secure for a solid diffuser this size.


    -Marc

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