Strobes watts/sec...What does that mean in output?

Discussion in 'Photography Equipment & Products' started by BLD_007, Mar 21, 2010.

  1. BLD_007

    BLD_007 TPF Noob!

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    So I'm looking at getting some strobes for portrait work and other applications.

    For every 100watts, do you gain 10feet in light output or something like that?.
     
  2. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    It's not that simple.

    Strobes are usually rated in Watt Seconds (Ws). The more Watt Seconds, the more power/energy is being released when it fires.

    That doesn't directly relate to photography terms though. The actual output of light will depend on the design on the light and whatever modifiers are used. For example, you may get more light (to a certain area) with a softbox, than with an umbrella. You will get even more with a reflector dish, but the light will be harder.

    So a strobe with more Watt seconds, will output more light, which can give you more range, or allow you to shoot with smaller apertures, but the exact amount will depend on the modifiers.

    A flash unit, on the other hand, is usually rated by a Guide Number (GN). This is because they are often used without modifiers and have a built in reflector dish and lens. The GN divided by the distance to the subject, will give you the F number needed for proper exposure.
     
  3. Alpha

    Alpha Troll Extraordinaire

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    For clarification, a watt*second is a joule, which is a unit of energy, not power.

    Also, strobes technically have guide numbers, too.

    Anyway, I'd aim for something in the 600w/s neighborhood. 300 can leave you feeling limited, and 1200+, for the average photographer's uses, is overkill.
     
  4. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    Ah yes, thank you.

    Yes, but pretty much need to specify the modifier to go along with a given GN. For example, you might say it has a GN of 100m, with standard/stock reflector. Of course, a bare strobe will have a GN, but that's not typically how you'd use it, so it doesn't mean much, IMO.
     
  5. BLD_007

    BLD_007 TPF Noob!

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    I just don't want to run into the problem of not having enough power if the strobe needs to be mounted somewhere.
     
  6. Alpha

    Alpha Troll Extraordinaire

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    What do you mean by, "if the strobe needs to be mounted somewhere" ?
     
  7. BLD_007

    BLD_007 TPF Noob!

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    ceiling of an arena for basketball tournaments or a ceiling of a gym for normal basketball games. In other words, far away and not close up.
     
  8. KmH

    KmH Helping photographers learn to fish Supporting Member

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    That means the "Inverse Square Law" comes into play.

    Light falls off as a square function to distance. If you double the distance to the subject, only 1/4 as much light reaches the subject. If you double the distance again only 1/16th as much light reaches the subject.
     
  9. JimmyO

    JimmyO TPF Noob!

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    I feel like everytime you post your getting ahead of yourself. Last week your were asking whats a fast lens now you have all L lenses and think you know what your talking about with strobeing a basketball game but your making yourself look dumb.
     
  10. BLD_007

    BLD_007 TPF Noob!

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    I have always had L. I have had my 70-200L for over a year. I just got my 24-70 about two months ago.

    Don't call me dumb, I know more than you think.

    I also have strobed basketball, diving, and dodge ball games. The thing is, I have not used my own strobes. I have always used the schools strobes. I want to get my own now. I just want to buy the most powerful ones that I can. I don't want to buy too weak and wish I had more.
     
    Last edited: Mar 22, 2010
  11. BLD_007

    BLD_007 TPF Noob!

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    I also have always know that the lower the apature the more light that hits the sensor. Last week I asked why it was called "fast" the term fast. Why FAST was used.
     
  12. Village Idiot

    Village Idiot No longer a newbie, moving up!

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    He's posting legit questions. You're making yourself look like an ass, as usual.
     

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