Combining flashes question.

[Kev M]

Reet then, i've not got three flashes and two radio triggers so if I want to use all three then one of them is going to have to be used with the in built slave cell.

If I combine two flashes to fire at the same time then the GN of the combined lights is higher than that of the single light (of course) but if I use one as a slave there is a momentary delay in the flash firing. So.....

1) Is the delay so long that one flash fires after the other has finished, thus not increasing the guide number but increasing the flash duration? Or

2) Is the operation of the slave so quick that they do effectively work as one light?

 

[chuckles]

The output from the gun with the biggest guide number (GN) is the only one you should take into account (unless the others are so ridiculously close to be laughable). There are always exceptions to rules...

Base your exposure on the the most powerful gun and ignore the delay between triggers through Infra Red or radio as it is negligible (unless your photographing speeding bullets) [the exception to the rule thing again!] :shrug:

They work as one but the most powerful is THE one! You can't 'add' to the power through the addition of GNs

 

[Kev M]

They work as one but the most powerful is THE one! You can't 'add' to the power through the addition of GNs

According to my copy of Light, Science and Magic if fired at the same time you can add power.

CGN = (sq rt of N)x GN1 Where N = the number of flashes and GN1 is the Guide Number of one flash (this only really works with flashes of identical power).

So in theory my 2 nikon flashes (GN32) should become GN45 when paired up. But I don't know if this will be true when one is used to fire the other through a slave as opposed to both firing at the same time through a radio trigger.

 

[chuckles]

CGN = (sq rt of N)x GN1 Where N = the number of flashes and GN1 is the Guide Number of one flash (this only really works with flashes of identical power).

Perhaps it is Magic then...... that's where I was going wrong.... never had two identical guns before. Now I have two guns {SB800s} I either use a flashmeter or iTTL in camera!

GN45 sounds right for two guns of GN32..... but they have to be totally synchronised otherwise you have two distinct sources!

Sorry to confuse!

 

[Irritable_Rabbit]

So in theory my 2 nikon flashes (GN32) should become GN45 when paired up. But I don't know if this will be true when one is used to fire the other through a slave as opposed to both firing at the same time through a radio trigger.

Really, the relative flash duration lasts for years compared with the speed of light firing of the slave flashgun. Just treat it as simultaneous firing.

 

[King_Boru]

I either use a flashmeter or iTTL in camera!

I'll second that, I always use iTTL in camera with my Nikon CLS lighting system. Easy, quick and reliable. The three key features to succesfull flash lighting during wedding photography.

 

[W.Smith]

Yes, Kev, the operation of the slave is indeed so quick* that your flashguns do effectively fire as one synchonized pulse.

*the speed of (infra red) light is 195,000 miles per second

Have fun!