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20x20 overhead with eggcrate (1 reply)

4 months ago
G.C. 4 months ago

Hi folks,

We’re filming a theatre play and the set size is 15x15ft (in a 50x50ft stage) and we’re thinking of using an overhead 20x20 full grid frame with an eggcrate (probably 40 degree) which will fly between 10-12ft high. Hard lights from movers up in the grid 22ft high would aim at the frame in different places and with various beam angles (and colors) to create soft or harder too lights, pools of light, and dynamic effects. 
I have an image in my mind of what it will look like but I would love your input… How much spill do you see happening? If I shine a light on the frame right in front of a human subject as a top-ish key light, how much raccoon eyes will I get? Will I get a nice angle for a backlight and maybe a far side key ? We can have light and grip on the floor, too.



3 months ago
gabj3 3 months ago

Your egg crate essentially makes your source smaller in relation to your subject. So dependent on the size/length of each cell... the degree of egg crate used will be the limiting factor in terms of wrap from your large source.

In your example, you have a 40 degree egg crate which describes the maximum angle of off normal axis light from the top of the cell to the bottom of the cell. 

With that, at 12' height your frame has a total dimension of 8x8' (with a 40 degree egg crate).

This is assuming the subject underneath is 5-6' in height and the characteristics you desire are around the subjects head. With this, if one was to quantify the softness of light - as say the total wrap around a the circumference of a sphere (approximately the size of a human head) you'd have a coverage of 254 degrees approximately.

This does of course cover a fair amount of the sphere which showcases a reasonably large amount of wrap. For reference it's a similar 'softness' of light to your 20x20 frame at around 15'.

I've got a calculator for photometrics from large diffusers/reflectors if needed.

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