How Many W/S to Over-Power Sun?

Looking at a single strobe shot through a large octa. Probably 8-10 feet away from subject shooting in full midday sun.

I know there are other variables, but is 660 w/s enough? Would I really need to step up to something like 1300+?

I usually don't go by watt seconds, as each flash manufacturer can have different variables.

Keep in mind the 'sunny 16' rule. 1/ISO at f16 is where bright sunlight exposure generally falls (for starters). That said, if you're max flash sync speed is 1/250, at ISO 100, your base exposure for bright sunlight would be 1/250 @ f11. If you can get your flash to output f16 or higher, then you will be able to 'overpower' the sun.

Take some meter readings, do some tests. Obviously the more power you have to work with, the better. It's the light modifier that will eat up your power, and 8-10 feet is kind of far back.

The choice of modifier will influence the power consumption as well.

I find my Mola Setti to be very efficient... compared to a conventional softbox.

Same with say... a silver umbrella vs. white.

Just something to keep in mind.

Peacefield wrote in post #13336815
Looking at a single strobe shot through a large octa. Probably 8-10 feet away from subject shooting in full midday sun.

I know there are other variables, but is 660 w/s enough? Would I really need to step up to something like 1300+?

At that distance with a softbox you may be pushing it.

I was trying to shoot two people with a large softbox at 10'-15' with a B800 that's 320W/S, iirc, and it wasn't working. 660w/s is only about a stop more. If you get the lights closer, then you should be better of, depending on how much you want to over power.

I now have a 6 stop ND filter and a 1200w/s pack. That works well.

If you're working your modifiers fairly close to the subject you'll be able to do it without having gobs of power.

If you're planning on pulling the modifier back to ~8 or 10 feet then you're going to need to ramp up the power quite a bit.

I've had many times where 600 Watt seconds isn't cutting it and another stop of light would have helped, but that extra stop would mean having 1200 Watt seconds and once you need that kind of power then you're looking at a lot more money.

Unless you absolutely must shoot under midday Sun, the best solution is to either shoot at other times of day when the Sun isn't directly overhead or to find a shaded area or one with dappled light.

PCB 640-660Ws, 8.5" reflector (45° spread): f/22 1/10 at 10 ft (from PCB)
Elinchrom Quadra 400Ws, 7" reflector (48° spread): f/16 3/10 at 10 ft (measured)

I'm going to make the assumption that the output from an 8.5", 45° reflector is comparable to a 7", 48° one. Given that, there's a 0.6-0.7 stop difference between the 400 and ~650Ws, so PCB's numbers can be taken as accurate. Knowing that, according to PCB you'll need 1320 Ws at 10' with a double-diffused softbox.

I think 6' or less is a more reasonable target.

http://www.paulcbuff.c​om/output.php

Peacefield wrote in post #13336815
Looking at a single strobe shot through a large octa. Probably 8-10 feet away from subject shooting in full midday sun.

I know there are other variables, but is 660 w/s enough? Would I really need to step up to something like 1300+?

Yes. 1300+ would be more like what you need.

'Over-Powering' the sun at 8-10 ft in a large octa will definately need more than 660w/s. At 8-10 ft you will be just on the edge of 'balancing' the sun, so requiring this specific distance will determine the output you need.

Thanks, everyone. I'll hope to shoot at closer distances, but 1320 it is.

Going back to some measurements which I posted on POTN a very long time ago:

Dynalite M500 (500 w-s full pwr) would yield f/16 at 4' or GN64 -- in a 24"x36" softbox. The softbox used was losing about -1.25EV So using this setup I could equal the sun only out to 4' light to subject. (Sunny 16 rule predicts that on a Sunny day with ISO 100, 1/100 f/16.)

Extrapolating from those past results...
Doubling power (1000 w-s) would result in f/22 with same softbox, or GN90, or f/16 out as far as 5.6'
Quadrupling power (2000 w-s) would result in f/32 with same softbox, or GN128, or f/16 out as far as 8'

toxic wrote in post #13337249
http://www.paulcbuff.c​om/output.php

Hey, thanks for this. As much as I've tooled around this site, I don't think I had ever found this little utility yet!