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<blockquote data-quote="WayneF" data-source="post: 383569" data-attributes="member: 12496">Two equal bulbs are twice as bright as one, which is one stop.Four bulbs are 4x, which is 2 stops.Doubling the number of bulbs is one stop (eight is 3 stops more than one).That is the problem with continuous light (dim).&nbsp; It never does the camera any good unless the shutter is actually open.So... 500 watts and a 1/100 second shutter is 500 x 1/100 = 5 watt seconds of energy converted to light (all that is usable).Speedlights are 60 to 75 watt seconds.&nbsp; Vastly more efficient.&nbsp; And they&nbsp; are fast, can deliver it all into any shutter speed (up to 1/200 second&nbsp; sync speed).Incandescents have much less efficiency than CFL or LED.&nbsp; Hotter too, since the power mostly goes into heat. This is the conversion when 26 watts CFL is called 100 watts, because it is equivalent light to a 100 watt incandescent -but only draws 26 watts power (and heat).</blockquote>

[QUOTE="WayneF, post: 383569, member: 12496"] Two equal bulbs are twice as bright as one, which is one stop. Four bulbs are 4x, which is 2 stops. Doubling the number of bulbs is one stop (eight is 3 stops more than one). That is the problem with continuous light (dim). It never does the camera any good unless the shutter is actually open. So... 500 watts and a 1/100 second shutter is 500 x 1/100 = 5 watt seconds of energy converted to light (all that is usable). Speedlights are 60 to 75 watt seconds. Vastly more efficient. And they are fast, can deliver it all into any shutter speed (up to 1/200 second sync speed). Incandescents have much less efficiency than CFL or LED. Hotter too, since the power mostly goes into heat. This is the conversion when 26 watts CFL is called 100 watts, because it is equivalent light to a 100 watt incandescent -but only draws 26 watts power (and heat). [/QUOTE]

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