Help me narrow the field.

I purchased a two light kit of the Calumet Genesis 200s with stands and umbrellas. I actually love the lights but think I might want more power. However, if I do buy something else I want to make sure I have a lot of flexibility so I don't just end up replacing those later on.

So first, is it BASICALLY true that all else being equal, 400ws strobes would provide the same light intensity as my 200ws strobes at double the distance? What about 600ws strobes? I assume its not the same intensity at 3x the distance, that would take 800ws strobes right? And more subjectively, how much more powerful are 400ws strobes than 200ws? I want to make sure I understand this basic concept before I determine what kind of power I need.

Second if I'm going to buy something new, I want something I can use off a battery for outdoor use.

Ultimately what I'm looking for then is brands that meet the criteria of more power than I have now (and I'll have to figure out how much I need) and the ability to run off a battery pack type of deal.

30 views and no input on the objective questions about lighting power?

No, not half, but 1/4. Inverse square law - http://photofocus.com …f-the-inverse-square-law/

But there are other issues with just moving a light back. Softness is a property of the size of the light source relative to the subject. With a given umbrella/softbox the closer it is the softer it will appear and vice-versa. I don't know about subjective power but a 400w/s strobe is twice the power of a 200 w/s strobe. but no matter the power, the inverse square law is still in operation.

I've read tests on the Genesis 200 working on Vagabond batteries. I've not seen the same info on the Genesis 400.

Hawki - The Genesis 400's are twice as powerful as the 200's, so at the SAME DISTANCE as your 200's ... they'll give you one more full f-stop of light to work with.

The other topic you mention is distance from light to subject. If you DOUBLE the distance ... your light is cut to 1/4 what it was at the shorter distance. Not 1/2 the power as you might think at first. Saying it another way ... if you wanted the same amount of light at double the distance as your Genesis 200, you'd theoretically need an 800 watt/second light.

I understood the issue with the "relative light source size" but obviously had the distance aspect wrong. Thank you! So with that said, if I want to be shooting outdoors, do I need something more powerful than say the AB 1600? That's only 640ws right?

If you are shooting outdoors with monolights there are several factors;
Essentially, the strobe requirement is based on the ambient exposure settings necessary to keep the shutter speed below the camera sync speed.

Using "Sunny 16" as a guide, at ISO 100 with a 1/200 X sync the F stop has to be F11 to properly expose a sun lite environment. If your current strobe, at 4 feet from the subject can deliver F16 at ISO 100, then you can underexpose the background 1 stop.

Using a mono twice as powerful at 4 feet means you can underexpose the background 2 stops, etc.
Moving the the light back to 5.6 feet would require using a strobe twice as powerful to get the F16 one stop benefit. Moving the strobe back to 8 feet would require doubling the power again.

Notice that I am using distance from the subject in feet increments that are the same as full F stops. That is an easy way to estimate what power setting is required when moving a light in or out.

Knowing that at full power with modifer A in place delivers F11 at 8 feet makes it much easier to set up lights, whatever the situation. Metering and fine tuning is still required but at least you have a good idea where to start.

Thanks guys, that makes sense. I need to meter my lights with modifiers in place I guess.