Does 2400ws strobe produce the same light as one 4800 strobe?

[D_Quinn]

Do two 2400ws strobes (using one head for each generator at full aiming at the same subject) produce the same amount of light created by one 4800ws strobe (say Speedotron) or the equivalent of the light produced by 3600ws strobe?
I need a lot of light for the wet plate photo shoot.
Sorry if this question has been asked before.
Thanks in advance.

 

[AgX]

If the transfer of electric energy into light is the same (which I assume at least for same manufacturer) I say 2x 2400Ws single units = 1x 4800Ws unit.

But then you still have to look at reflector geometries, which may affect spill and lighting angle. Also the output-time depends basically on flash capacity.

 

[D_Quinn]

Hi AgX, Thank you for your answer. Now it is clear!

 

[AgX]

Actually it is a good question. One of these where at once one may think the answer would be obvious, but then may start contemplating whether there not might be a hidden issue.

 

[AgX]

Another issue may be UV output. If the tubes or the safety domes differ on this, it may affect exposure of unsensitized plates as yours.

 

[Donald Qualls]

A flash meter would tell you for sure.

That said, I've never owned one. I've used Guide Numbers for the past fifty years.

 

[TheFlyingCamera]

While two 2400 ws packs firing simultaneously SHOULD be equal to 4800 ws from a single pack, assuming all other things are equal (lamp heads, reflectors/modifiers, quality of electrical supply, etc), this is true for a single pop of the flash, not necessarily if you are doing multiple pops. While two pops of 2400 ws worth of light from a single pack will most likely equal the output of 4800 ws worth from a single pop, reciprocity does kick in with flash exposures as well... so if for example you determine that you need f/32 on your lens, and you can only get f/8 with a single pop of your flash, f/32 at 5 stops slower wouldn't be 16 pops, but probably something like 24-32 pops.

 

[D_Quinn]

Thanks, everyone for your additional useful comments.
I didn’t know that I need to think about reciprocity failure for multiple flash lighting… It is very informative! really appreciated it

 

[AgX]

I do not get this idea of reciprocity failure due to multiple flash lighting.

Such would necessitate a difference in lighting time by several magnitudes* between those multiple flashes and that stronger single flash.
Such is real with those small, cameramounted auto-exposure flashes. They got full power lighting time of 1/1000 or longer but can reduce that by several magnitudes.

I do not see this at studio generators.

Maybe TheFlyingCamera makes us wiser on this point.




* I am referring to modern, gelatine based halide materials, the reciprocity effect at collodion plates may be somewhat different.

 

[TheFlyingCamera]

I do not get this idea of reciprocity failure due to multiple flash lighting.

Such would necessitate a difference in lighting time by several magnitudes* between those multiple flashes and that stronger single flash.
Such is real with those small, cameramounted auto-exposure flashes. They got full power lighting time of 1/1000 or longer but can reduce that by several magnitudes.

I do not see this at studio generators.

Maybe TheFlyingCamera makes us wiser on this point.




* I am referring to modern, gelatine based halide materials, the reciprocity effect at collodion plates may be somewhat different.

I'll have to look up my source for this. I remember learning about it from my studio lighting class at university (in the 1990s) but I will get you something more definitive.