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Dennis Hingsberg

amount of light from bounce on 6x6 ?

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I'm on a super budget and will need to carefully select the lights I will be renting for an upcoming film shoot.


The scenes take place in a dark no-natural light location so I plan to create some light shafts coming in through some background windows using hazer and tight focused light beams, then use muslin (or possibly other bounce or shoot-through) as a soft key.


What I'm wondering is what kind of photometrics I can expect from bouncing into the muslin depending on what lights I decide to go with? Obviously distance is a factor, but I'm looking for even some approximations so I know where to start. The rest I can scrim down, dim, or use distance to help me get to where I want to be.


Anyone have any footcandle approximations using a 2k tungsten or 575w HMI, or 1.2kW HMI at 10, 20 or 30 feet away? bounced or shoot-through?


Cheers, thanks,




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Stephen Murphy and Ed Moore did some tests with different diffusion materials and how many stops you have to compensate in order to get the same exposure as without the diffusion.


At this site there is also a vimeo link to the video they made. I hope it helps you a little bit :)



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Thanks Daniel.,


Looks like a great fabric shootout that gives some idea of the exposure differences between fabrics. I was hoping for some data on bounce, but shoot through is also good to have. I'll have to ask them what f/stop they shot with and if any ND's. It would reveal a lot more about the photometric data and more specifically the loss of light transmission from the light source itself to the subject.

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My own testing continues,


Today I bounced a 575w 19 degree Source 4 on 4x4 bleached muslin at about a 45 degree angle from 6 feet away. At 7 feet from the muslin I measured 15 foot-candles. The direct light hitting the muslin measured 1920 foot-candles. This is equivalent to 7 stops of light loss.


15 foot-candles is enough to give you between f2 and f4 if shooting between 800 and 1250 ISO.


Anyone else feel these values are accurate?

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