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Old Mar 22, 2006, 11:33 AM   #1
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could some one please explain to me what the levels equal to. I shoot with a sunpak 544 55 and 622. So for example when i have the flash on full power or half power what does that equal to in shutter increasse and F stop.
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Old Mar 22, 2006, 11:53 AM   #2
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The two can't really be equated.

The full/half/quarter are power settings to the flash, but the actual light output depends on the unit itself. Half the power does not mean half the light output.

A 100 watt second flash will make a bit more light than a 50 watt second unit and much less than a 500 watt second flash.
It dosen't end there, the light output is also affected by the efficiency of the flash tube and the reflector and lens if the flash has one.

This is where a lot of confusion comes about with some manfacturers claming higher effective output vs true output like the Alien Bees do.


The only way you can really tell how much light is being generated is is to measure it either using automated camera TTL function or with a flash meter.

It can also be worked out if the flash manfacturer gives you the Guide Number for each power setting on a unit.
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