Re: Question on flash and power or intensity measurement.

Santa Fe Imaging <herschel@xxxxxxxxxxxxxxxx> · Sat, 19 Oct 2013 08:55:06 -0600



    Jan you are too funny!... This
        doesn't need calculus... Your math is very dubious. It's like
        that joke about the three guys who buy a car and get short
        changed. (what happened to the other ten bucks?)

        
        Or you must work with a 500 ws flash unit from hell. I remember
        shooting cars with 4000ws packs and having to multi-pop them...
        

        according to your arithmetic, there must have been something
        radically wrong with those Elinchrom packs.

        
        THINK JAN! a 500ws strobe isn't that powerful.... 

        
        1. a grey card up on a wall and spot meter in hand

        2. a 500W tungsten light 10 feet away covering 100 sq feet of
        wall. 

        3. take a reading at 1 second...and get say  f/16

        4. replace the Lowell light with a strobe... same distance and
        same coverage Use flash meter to get reading... (shutter speed
        is obviously irrelevant)  you'll get close to the same f/16.

        
    4. replace the halogen lamp with a 500ws

    2 a 500 10/19/2013 8:10 AM, Jan Faul wrote:

    
      Did you do well in math? Can you explain how a 500 watt
        tungsten bulb can deliver the same light as a 500ws flash
        delivering light in 1/175th sec? 
      

      Take one second and divide by 175 = and multiply the result
        by a big enough number to equal 500. Got it? That’s how many
        tungsten watts equal a 500 ws studio strobe.
      

        On Oct 19, 2013, at 10:00 AM, Santa Fe Imaging wrote:
        

           There are all kinds of mechanical and
                electronic considerations that come into play but it
                seems to me that a 500 watt tungsten lamp exposed for 1
                second should give the same amount of light to the
                sensor/film as a single 500ws flash exposure.

                
            On 10/19/2013 7:34 AM, Andrew
              Davidhazy wrote:

            
              I think that something vexing is the fact that the electronic flash delivers its light over a short time while tungsten lamps can (or do) deliver it over a long time. If one compares them at the assumed duration of the flash then the tungsten bulb will come out the weaker of the two by far. But if you compare them during an exposure time of a second or a minute or more then the tungsten lamp wins. It seems to me anyway.

Andy from Rochester


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