guide number Watt Seconds Effective Watt Seconds BCPS (Beam Candle Power Seconds)
16x the light. However its a largely irrelevant measure; GN is completely dependant on any sort of reflectors, diffusers, zoom heads etc etc. So on a white lightening, this figure changes with anything you put on it. As does the 540, but this is less common of course.
This is of course also why the 540 changes GN with zoom position; the Watt-Seconds would be the same no matter what; it is an absolute power.
Howeer even this is misleading, as it is the amount of power the flash uses, not how much light it puts out. Different efficiencies etc can make this vary somewhat; and it is often only truly useful when comparing a range from one manufacturer.
I've not seen BCPS much, but I assume its the american or imperial equivalent of Lux /Lumens/Candela? In any case, this is potentially the most useful, but least quoted spec.
- Peter -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
