This is topic Calculating stage lighting needs in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Adam Martin (Member # 641) on 10-18-2002, 12:25 AM:
I'm in the process of re-doing our preshow and presentation lighting and I will need to purchase some stage lighting soon.What I need to know is how to calculate the size of the fixtures. If I want to shoot a 72-inch diameter circle of light 35-40 feet, what size ellipsoidal should I use? Is there a mathematical calculation based on lens diameter, focal length and throw distance? And then, is there a conversion for angular measure (ie, does a 6x18 put out a 10-degree cone)?
I should have paid attention in math class.
Posted by Paul Mayer (Member # 355) on 10-18-2002, 01:27 AM:
A 6x22 has an 11 deg. spread and will give you a 8' spot at a 40' throw. One can also get these instruments fitted with an iris in the gobo slot to allow narrower beam widths.
A chart from the nice folks at Altman Lighting:hereJa ne,
Paul
Posted by Frank Angel (Member # 248) on 10-18-2002, 11:44 AM:
Yeah, we all should have paid more attention. This should help: go to http://www.altmanltg.com/
Under "Product Index" - "Ellipsoidals" are the photometrics for Epical Altman instruments. ETC Source 4 info is at www.etcconnect.com
Good luck.
Frank
Posted by Frank Angel (Member # 248) on 10-18-2002, 11:46 AM:
woops, sorry, didn't see Paul's post. That's the place.
Posted by Gordon McLeod (Member # 33) on 10-18-2002, 12:06 PM:
Check out the source4 fixtures with the precision glass reflectors they do the best job and if only a few are required they would fit a budget as they are pricy
THey also have an option of an onboard DMX controled dimmer