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Diffusion Scrim question: Two 4x4s or one 42x72?

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chris pike
Diffusion Scrim question: Two 4x4s or one 42x72?
on Mar 27, 2018 at 1:30:32 am

I have to light a standing model from head to toe. I'm using two led panels, one at knee height and one at about 7 feet up (and pointed slightly down). The following question may seem trivial, but there is actually a few hundred dollar on the line. I could buy two solid 4x4 diffusion frames, or I could buy one collapsable 42"x72". The 42x72 isn't quite tall enough, but using 2 4x4s is going to leave a slightly dark region in between. There is no perfect option, but which way would you go?


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Rick Wise
Re: Diffusion Scrim question: Two 4x4s or one 42x72?
on Mar 27, 2018 at 2:09:05 am

If you are on a stage, you don't need a frame at all, just a C-stand and a roll of diffusion that you slide onto the C-stand's arm and roll down to the height needed.

Rick Wise
Cinematographer
MFA/BFA Lighting and Camera Instructor Academy of Art University
San Francisco Bay Area
http://www.RickWiseDP.com


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Todd Terry
Re: Diffusion Scrim question: Two 4x4s or one 42x72?
on Mar 27, 2018 at 2:15:25 am

Yep Rick is right, as usual. You don't need a frame, or even have to cut your roll of diffusion... just slide the roll onto a grip arm.

And if you want to sound like you know what you are doing, this technique is known as "Hollywooding."

T2

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Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com



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Rick Wise
Re: Diffusion Scrim question: Two 4x4s or one 42x72?
on Mar 27, 2018 at 3:13:16 pm

Hmmmmm...... I always thought "hollywooding" means hand-holding some item like a scrim or silk during a shot, often moving with the action.

See: “If somebody tells you to ‘Hollywood’ something on a set,” Barry explains, “it means don’t take the time to put it on a stand, just hold it and hold it where it needs to be.”

Barry says the reasons for Hollywooding a light or other piece of equipment range from being in a hurry to working in a space where there isn’t room to set up a lot of stands and other gear.
(https://blogs.mprnews.org/state-of-the-arts/2011/03/arts-101-film-and-vide...

Rick Wise
Cinematographer
MFA/BFA Lighting and Camera Instructor Academy of Art University
San Francisco Bay Area
http://www.RickWiseDP.com


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chris pike
Re: Diffusion Scrim question: Two 4x4s or one 42x72?
on Mar 27, 2018 at 6:48:35 pm

RE: Roll of diffusion. I have been told that the model will look better if the top light (seven feet high) is aimed slightly downward on the models face. If a roll of diffusion paper is vertical, then won't the downward tilt of the top light be removed when it meets the models face? To keep the downward angle of the top light, I think I need to tilt the diffusion scrim as well, which would be difficult with a roll of paper. No?


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Rick Wise
Re: Diffusion Scrim question: Two 4x4s or one 42x72?
on Mar 27, 2018 at 7:35:48 pm

Assuming your diffusion is set at least a couple of feet away from the light source(s), a "slight tilt" of the light(s) won't make much difference if the sheet goes straight down to the ground. Note that you can grab the bottom of the rolled-out diffusion and pull it so the roll is parallel to the tilt of the light(s). Just anchor the bottom with some convenient weight or clamp(s). Use a clamp to keep the paper from rolling further off the C-stand arm.

Experiment! Play!

Rick Wise
Cinematographer
MFA/BFA Lighting and Camera Instructor Academy of Art University
San Francisco Bay Area
http://www.RickWiseDP.com


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Bill Davis
Re: Diffusion Scrim question: Two 4x4s or one 42x72?
on Mar 31, 2018 at 9:08:36 pm
Last Edited By Bill Davis on Apr 1, 2018 at 4:51:01 pm

Think of it this way.

No matter the size or shape of the diffusion your goal is lighting an object (say a 6' tall person) from head to toe.

Say you only have ONE light. If you position that light in the middle, the strongest photons are coming from the brightest middle area of the diffusion and spreading up and down onto the subject. If you move that light UP to the top of the diffusion, the strongest photons come at the subject from higher up - (and as critically, there is now much more distance that those photons have to travel to reach the model's feet. So the inverse square principle tells you that his or her feet, will have a lower illumination level than their hair.

See how it works? The position of the illuminating instrument STILL effects which parts of the subject gets the most light even with diffusion in between. The key is the distance the photons have to travel since the inverse square principal dictates that they lose a lot of their energy over distance.

If you want to control the apparent brightness of areas of the subject, just adjust the position of the light sources relative to the subject.

If you want a brighter top, then light up the top of the diffusion with one light, and fill the middle and lower zones with the second source.

Hope that helps.

Creator of XinTwo - http://www.xintwo.com
The shortest path to FCP X mastery.


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