How do you determine the f-stop of a flash w/out hand held meter

I am confused on how you go about trying to calculate how to set your flash (Canon 580EX and 430EX) to a specific F-stop without using a hand held flash meter?

I have read on the Strobist webpage and also the book the "Minimalist Lighting" that for example if you manually set your camera for the ambient light reading of say 1/60 F 8.0 then set your flash to F 5.6

I understand that your aperature controls (has a greater effect) of the quantity of light via flash and the shutter speed will control (greater effect) of the quantity the ambient light. But how can you tell what aperature/F-stop the flash output actually is?

The flash or flashes including the camera would all be in manual mode with the flashes being trigger via wireless remote (flashwaves). I have used the flashes with the off camera cord (OC-3?) and I have set various ratios (580EX set as master / 430EX set as slave) using E-TTL the cord is really too short and really limits where I can place the 530EX flash with respect to the camera and if you move to far flash and light stand moves or threatens to fall... a real pain in the backside to say the least. I think I am ready to have more control.

Is there a given starting point as far as the setting for the flash which gets you close then you just fine tune with a couple of test shots? I've read there is but how do you know where to set your flash without know what aperature it is outputing for?

Help!!! Thnx
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JM

http://www.photosbyjonathan.phanfare.com
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