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#1 Joseph Zizzo

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Posted 18 September 2009 - 01:15 PM

i'm doing a scene with a guy doing a presentation with a slide projector, shooting on the red... which i like to rate no higher than 250 ASA. do any of you now if a 3000 lumens lcd slide projector will be sufficiently bright, 8-10' from the screen in a conference room scene, shooting at f2 - 2.8. the image on screen should be the brightest thing in the room, balanced against a subdued daylight, 2 stops under or so, with the drapes closed.

i have only used big massive projectors, 10k lumens and up, for lighting effects, so it seems like a 3k lumens projector 10' away should suffice, but i'd like to be sure.

my real challenge is, i can't seem to find find a concise way to convert lumens to f-stop/footcandles. i know 1 footcandle = 1 lumen /sq foot, but what is the next step in converting the lumens rating of an LCD projector to footcandles, so as then to derive an f-stop? i'm obviously no math whiz, but a simple explanation may be all i need.


thanks in advance...

joe
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#2 Joseph Zizzo

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Posted 22 September 2009 - 11:11 PM

ok don't everyone talk at once...!

so we ended up with a 5k lumens projector, just by virtue of the rental house the prod designer went to, and it was just about right after some half CTS and minusgreen were added... for all it's virtues, that RED is a light-sucker, to be sure.

just thought you'd like to know!!

joe
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#3 Sean Farrington

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Posted 06 November 2009 - 09:29 AM

Thanks Joe, This was extremely helpful. Sorry no one posted to help you, but you did help me. BTW i get the minus green but could you tell me what "CTS" is?

- sean
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#4 Frank Barrera

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Posted 06 November 2009 - 08:53 PM

Hey Joe,

Howz things? the last time I saw you we learned that sheep have zero problem climbing up stairs in a house but refuse to go down stairs.

Sean, CTS is Color Temperature Straw. It converts daylight to tungsten with an added yellow cast.
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#5 Sean Farrington

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Posted 06 November 2009 - 09:52 PM

Thanks Frank, very kind of you to respond :)

Hey Joe,

Howz things? the last time I saw you we learned that sheep have zero problem climbing up stairs in a house but refuse to go down stairs.

Sean, CTS is Color Temperature Straw. It converts daylight to tungsten with an added yellow cast.


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#6 Chris Keth

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Posted 07 November 2009 - 05:27 PM

I don't remember the formula (I could look it up), but I know you would need the reflectance (or transmittance if it is rear projection) of the screen in order to calculate footcandles.
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