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  1. #11
    Join Date
    Dec 2006
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    Toronto
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    how do i use this table to use the 3500xi flash manually?

    http://www.riversidecardiology.com/fstop/f-stop.htm
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  2. #12
    Join Date
    Feb 2006
    Location
    Des Plaines, IL
    Posts
    9,560
    Quote Originally Posted by cgl88 View Post
    how do i use this table to use the 3500xi flash manually?

    http://www.riversidecardiology.com/fstop/f-stop.htm

    This methodology is for use of two flashes ... not just one. Main and fill.

    From my current understanding, when you use a single flash
    1. You usually begin with controlling the lighting with a base shutter speed setting of 1/60th (this is the slowest real setting, that does not introduce noticable ambient lighting (which can lead to subject blur and color shift) in the image and syncronizes with the flash burst)
    2. Using a light meter ... "test burst" the flash, taken at the subject, to measure the incident light available. (This varies with distance, as all general light usually does.) This may take a couple tries, depending on how well you work with the light meter and how well your assistant, tripping the flash, works with you.
    3. Take setting the light meter has received and match your lens aperture to it.
    4. Make sure your ISO matches in both the light meter and that it is set in your camera.
    5. Pop a "test shot" and check your image. Looks good? Fire at will! Looks dark?


    Try the following:
    • a) Open the aperture to the next wider setting
    • b) Have you run out of aperture? Move flash closer ... or modify intensity of flash, with whatever adjustment may be available. Remeasure with the light meter, at the subject.
    • c) You can also ramp up the ISO to the next higher setting ... now this usually adds noise to your shot, so it should be your last alternative. The idea is to keep your image as clean as possible.


    Using two flashes moves you into ratio lighting. Under normal circumstances, you have a "main" flash and a "fill" flash, which you balance with one another to provide the lighting you want that will reduce or eliminate substantial shadowing from a single source of light. Depending on the placement of the two flashes, you render a different amount of drama to the shot.

    Use of a light meter, under this arrangement is crucial and minimizes the trial and error period enormously. You just need to understand what the light meter tells you when you make a measurement. Using two sources of light requires some understanding of the cummulative effect of photometry and you usually make three measurements.
    • The first measurement is with the just main on, to know how much light is striking your subject, initially.
    • The second measurment with just the fill on, to determine the ratio between the two and then
    • a third measurement with both on ... to find the overall exposure level for the light you are using.


    Seems simple enough, eh? Believe me, this is where the sweat begins.

    I won't go any further, for the time being ... because understanding the balance really requires you to actually do it and see the results for yourself.

    Remember that normal portraiture is a 1:2 ratio from one side of the face to the other. That means, for example, if your light meter measures f/4 on on side, it should measure f/2.8 on the other. The f/2.8 side being the darker side. When your subject says something like, "My left in my better side" ... BINGO, that's the one that gets the brighter light. Remember: The higher the f-stop indicated on the light meter the brighter the light source.

    You add drama by changing that ratio to things like 1:3 or 1:4. So, if you read f/4 on the one side, you should read f/1 on the other for a high drama appearance.

    Using three flashes allows you to backlight your subject ... but remember if you want the color of the background to be what the camera sees, your light intensity should MATCH your exposure setting, otherwise you darken or lighten the color accordingly. So, if you measure f/4 coming from the background ... your base aperture setting should be at f/4 ... and everything in front of it will have measure brighter (you have to supply more light) ... f/4+ to look correct, otherwise you get a reverse-shadow effect. Also, as you turn on your main and fill light, it will splash back add to this background lighting, if you are not careful of positioning.

    Four flashes allows for a "hair light", which is a narrow flash aimed at the rear or slight to the rear side of the subject, to provide a halo effect to thew hair, differentiating the hair from the background. It adds luster to a rather flat looking, undynamic exposure.

    This is work ... make no mistake, as you shape the lighting to reflect what YOU "want to see" ... and not always "what is there."
    Last edited by DonSchap; 07-20-2007 at 04:40 AM.
    Don Schap - BFA, Digital Photography
    A Photographer Is Forever
    Look, I did not create the optical laws of the Universe ... I simply learned to deal with them.
    Remember: It is usually the GLASS, not the camera (except for moving to Full Frame), that gives you the most improvement in your photography.

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