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I have been using continuous lighting for mannequin pictures and it was quite difficult to overexpose the background all the time however I made it work. Due to my dog ( long story) I am being forced to upgrade sooner than planned. I was wondering if two 160 watt strobe lights would be enough to over expose a 5x10' background. I am not concerned with perfect lighting on the subject at the moment — I just want the background to be a solid white (some refer to it as "high key").

  • Even a pocket flashlight or even moonlight can overexpose things on some shooting settings (the aperture wide open, exposure time long enough, ISO high enough)... Try to give better information on your setup, shooting conditions, distances etc. – user681768917 Jul 30 '15 at 6:20
  • Agree with user68... If you are photographing mannequin you do not really need a flash. The problem is the relation of light on the subject vs. the background, this could be solved adjusting distances between background-lights-subject-lights. – Rafael Jul 31 '15 at 16:58
  • High key is refering to the overall ilumination, not just if the background is white. – Rafael Jul 31 '15 at 16:59
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There are details... Flash is rated as watt seconds (electrical energy input). A continuous light is only useful for photography while the shutter is open. Watts is its rate of energy. A 250 watt continuous bulb through a one second shutter is 250x1 = 250 watt seconds, but at 1/100 second is 250x1/100 which is only 2.5 watt seconds. Huge difference.

The 160 watt second flash is 160 watt seconds at any shutter speed (up to camera maximum sync speed, typically around 1/200 second shutter)... 160 is another huge difference. And the flash is also maybe about 4 times more efficient than incandescent about making light from energy (efficiency about like fluorescent bulbs, instead of just making heat). So flash is a lot of light.

I'd say one flash does it, CERTAINLY AS COMPARED TO CONTINUOUS LIGHTS, but it depends on your exposure of course. A silly example would be that a flash metering f/5.6 will overexpose a f/4 exposure by one stop. 1/2 stop over should be enough to make a white background be very white (incident metering).

As an example of one case, the Paul C. Buff company (Alienbees, etc), publishes this chart: http://www.paulcbuff.com/output.php It says a 160 watt second Alienbees B400 flash with standard 7 inch reflector (80 degrees wide) has a Guide Number of 77, which is almost f/16 at 5 feet, ISO 100.

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The bigger problem will be getting even coverage. You typically expose the background one stop higher unless you want blowback on the subject.

Even a small strobe can expose a background to pure white with a large enough aperture setting.

So the answer is a qualified yes.

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