Ekij Posted February 24, 2005 Share Posted February 24, 2005 In Part 2 of Section 6.01 of The article "Stage Lighting Design" by Bill Williams (referred to in the FAQ section of The Blue Room) athttp://www.mts.net/~william5/sld/sld-600.htmsuggests that a 25 degree light will product a pool 12 feet in diameter at a distance of 50 feet. By my calculation it should be 50*2*tan(25/2) or 100*tan(12.5) = 22.2 feet.Has Bill made an error in this article or have I totally lost the plot? Link to comment Share on other sites More sharing options...
propmonkey Posted February 25, 2005 Share Posted February 25, 2005 In Part 2 of Section 6.01 of The article "Stage Lighting Design" by Bill Williams (referred to in the FAQ section of The Blue Room) athttp://www.mts.net/~william5/sld/sld-600.htmsuggests that a 25 degree light will product a pool 12 feet in diameter at a distance of 50 feet. By my calculation it should be 50*2*tan(25/2) or 100*tan(12.5) = 22.2 feet.Has Bill made an error in this article or have I totally lost the plot?<{POST_SNAPBACK}> I had that problem too. I used tan to figure out the spread of a strand 5 degree, it not accurate. the beam spread is not usually exact. for any degree take tan([half the beam spread]) and set it equal to half of the pool over the distance. for a 25 degree you should have. tan(25/2)=(x/50) then solve for x and multiply by 2. so at 50ft a 5 degree instrument would produce a pool of light around a little over 4ft. I could be wrong. Link to comment Share on other sites More sharing options...
stormster Posted February 25, 2005 Share Posted February 25, 2005 In Part 2 of Section 6.01 of The article "Stage Lighting Design" by Bill Williams (referred to in the FAQ section of The Blue Room) athttp://www.mts.net/~william5/sld/sld-600.htmsuggests that a 25 degree light will product a pool 12 feet in diameter at a distance of 50 feet. By my calculation it should be 50*2*tan(25/2) or 100*tan(12.5) = 22.2 feet.Has Bill made an error in this article or have I totally lost the plot?<{POST_SNAPBACK}> I had that problem too. I used tan to figure out the spread of a strand 5 degree, it not accurate. the beam spread is not usually exact. for any degree take tan([half the beam spread]) and set it equal to half of the pool over the distance. for a 25 degree you should have. tan(25/2)=(x/50) then solve for x and multiply by 2. so at 50ft a 5 degree instrument would produce a pool of light around a little over 4ft. I could be wrong.<{POST_SNAPBACK}> or cheat and use wysiwyg or ld assistant? Link to comment Share on other sites More sharing options...
Paul J Need Posted February 26, 2005 Share Posted February 26, 2005 Can I suggest you get a piece of paper, pencil and potracter (spelling?!?!?) - 22 feets seems more likely to me though ..... 50' is a long distance for a 25 degree to go Link to comment Share on other sites More sharing options...
Guest lightnix Posted February 26, 2005 Share Posted February 26, 2005 Mornin' Paul ;) Ah yes, the old methods are the best. Being cr :P p at maths myself, I always found it quicker to use a protractor to draw out the angle on a piece of paper and then measure off the relevant distance / beam size with a scale ruler. Tangents ? Link to comment Share on other sites More sharing options...
themadhippy Posted February 26, 2005 Share Posted February 26, 2005 Tangents ?A small male orange fruit,very popular around christmas Link to comment Share on other sites More sharing options...
paulears Posted February 26, 2005 Share Posted February 26, 2005 methinks the 12 feet is a maths ####-up. It is 12 feet from the centre to the perimeter - suspect he forgot to multiply it by two. My calculations say 22 ft too! Link to comment Share on other sites More sharing options...
Andrew C Posted February 26, 2005 Share Posted February 26, 2005 Tangents ? <{POST_SNAPBACK}> No, Tan; it's a bit like Sin & Cosine, but I long ago forgot WtF you use it fot. :P Link to comment Share on other sites More sharing options...
Bryson Posted February 26, 2005 Share Posted February 26, 2005 methinks the 12 feet is a maths ####-up. It is 12 feet from the centre to the perimeter - suspect he forgot to multiply it by two. My calculations say 22 ft too!<{POST_SNAPBACK}> [pedant]Wouldn't that make it 24 feet? Or the first number 11 feet?[/pedant] :P Link to comment Share on other sites More sharing options...
Freddie Posted February 26, 2005 Share Posted February 26, 2005 No, Tan; it's a bit like Sin & Cosine, but I long ago forgot WtF you use it fot. <{POST_SNAPBACK}>Tan being short for Tangent, Sin for Sine, and Cos for Cosine IMSHOMIC (If my School's Head Of Maths Is Correct) [/super-pedant] Link to comment Share on other sites More sharing options...
Jivemaster Posted February 26, 2005 Share Posted February 26, 2005 SOHCAHTOA Link to comment Share on other sites More sharing options...
Freddie Posted February 26, 2005 Share Posted February 26, 2005 Helpful mnemonic for that:Sex On HorsebackCan Always HappenTo Our Amazement Link to comment Share on other sites More sharing options...
paulears Posted February 26, 2005 Share Posted February 26, 2005 If I'm reading this thread properly, are we to assume trig isn't taught anymore? Fai enough it isn't exactly in daily usage, but it's quite useful to have in your head when someone asks about beamspread or diagonal rope lengths etc Link to comment Share on other sites More sharing options...
the kid Posted February 26, 2005 Share Posted February 26, 2005 It is taught but is not really taught. From this I think I might go over my trig again. Link to comment Share on other sites More sharing options...
Freddie Posted February 26, 2005 Share Posted February 26, 2005 I got 10x45 minute lessons on it a few months ago (top set out of 6) They tell me its still an important part of the GCSE/Alevel/IB course. Link to comment Share on other sites More sharing options...
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