When two or more flash are used together in manual mode, how do I calculate the GN?


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mpenza

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#4
Originally posted by ckiang


Get a flash meter. :devil:

I DON'T think you simply add them up though I might be wrong.

Regards
CK
flash meter can do the calculation for more than one flash?

maybe I just try it out.... hopefully the auto mode itself can work ;p was asking cos the newly bought Nikon SB24 has a sync socket which could trigger my other flash, Metz 32Z1 :)
 

ckiang

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#5
Originally posted by mpenza


flash meter can do the calculation for more than one flash?

maybe I just try it out.... hopefully the auto mode itself can work ;p was asking cos the newly bought Nikon SB24 has a sync socket which could trigger my other flash, Metz 32Z1 :)
A flash meter will figure out the exposure required (usually in terms of f-number or EV) even with multiple flashes, even with some bounced, some direct, etc. :)

Auto mode might not quite take care of it, though TTL might.

Regards
CK
 

mpenza

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#6
was told in the DPReview forums that I need to sum up the square of the two GNs and then, take the square root of the result. calculated and it's 62m for my setup @ISO100 and 85mm zoom for both flash :)
 

beachbum

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#7
yep, use a flash meter.
some flash meter allow multiple flash reading and then even them out. anyway, flash meter will be able to read from more than one flash light.

use either TTL for both flash (if possible??).
I suggest sticking to manual is the best. Don't use auto mode as you never know how the flash would read the scene, and chances are, the output of one flash will affect the auto reading of the other flash.
 

denizenx

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#8
lol mpenza, that's what RMS means.. root of the two squares..
I think auto dun cater for slave adjustment, since there's no preflash nor *-TTL, unless they can do modeling strobe?
 

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