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Gels

Discussion in 'Lighting and Electrics' started by rgsw, Oct 3, 2004.

  1. rgsw

    rgsw Member

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    Has anybody succesfully mixed red green and blue spots to get white light? if so what gel numbers did u use? pref lee cause i'm a cheap skate .

    also i remeber someone once telling me that there is one magic gel that makes everybody look really healthy and rosey! does this exist if so what number?

    cheers

    ollie
     
  2. SuperCow

    SuperCow Active Member

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    Well, the "magic gel" you're talking about is probably R02, made by Rosco. I'm not sure if there's a Lee equivalent.
     
  3. JahJahwarrior

    JahJahwarrior Active Member

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    well, you would need to use the primary colors of those, not shades of them. I don't know which things are the primary ones, but it would probably be something like "light red" in Roscolux colors, for red. And, www.proadv.com they have Lee, Rosco and Gam gels for $5.15 each. Atelast, that's what I remember reading in their catalog last night....
     
  4. SuperCow

    SuperCow Active Member

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    Rosco actually has "Primary Red", "Primary Blue" and "Primary Green" in their collection. I forget their numbers though.
     
  5. ship

    ship Senior Team Emeritus Premium Member

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    Rx 02 is similar to Gam E #340 and Lee 162. Not sure of the Apollo number for it yet.

    From a strictly theoretical point of view:
    True white is subjective to the color temperature of lamp along with it’s individual spikes in the colors given off you are starting with. Add in amber shift from dimmed lamps or saturation levels of the gel not being similar in transmission ratio and if using more than one type of fixture, differences and ages of lamps in the light given off, plus any factors having to do with the lens itself. It’s also going to be a question of what the light is projected upon as to what color is most absorbed.

    For the most part, white light is especially with what surfaces it’s shined upon subjective so some amount of tinkering or what looks white but may not be true white will be a how it looks type of situation. If for instance you need to correct for a dimmed amber shift in the light, you might need a little more blue. On the other hand, if the scenery you project on is say green, you might need to head with the corresponding red and blue more towards the magenta range to get a white looking beam. Primary colors are a good start but there is a lot of modifications also.
     
  6. JahJahwarrior

    JahJahwarrior Active Member

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    what do youneed to do this for?? Ship is right, it is pretty complicated....but, the question is, if you are working on this for a show, why does it have to be this complicated? If you want white ilght, why don't you just not use a gel?? And if you need those other colors, then great, 4 lights. The other thing is, is it shining on a person? Or on a floor or wall or cyc? If it is on a floor, wall or cyc and you want it to make the object appear white, even if it's not, then ask Ship how to do that...I forget if you use the same color (green wall, green gel) or the opposite...

    anyways, Ship has raised some very important points!
     
  7. zac850

    zac850 Well-Known Member

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    I'm fairly sure that you would use the opposite color.

    Is there a certain effect you want to try, or do you want to try to make a pure white light. If it is the first, tell us what effect, we'll try to figure out an easier way. If it is the latter, then you can use a color correcting gel. Personally I like to use G870, it gives a very white light, even though not technically a color correcting gel.
     
  8. JahJahwarrior

    JahJahwarrior Active Member

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    I'msupposing you mean Gam870? (like, the G stands for gam?) the winter white thing? My shcool....they don't really know much about their setup, it's kinda funny, we rent the bulding from a church. They have gels, and they don't really ever buy new ones, but this year they are :) They have several that are close to this winter white, maybe closer to G872...they worked out GREAT for The Homecoming (the walton family) because it was a winter set. They provided jsut that hint of blue, making it feel almost cold and harsh. But this next play is a comdedy, they are getting new gels!!!!

    I do not know exactly what pure white is, but the color you want also depends on what color white..:) like, a bluish white, or more of that yellowish color? personally, I like to think of pure white light as the kind from bluish flourescent lights.

    this is the most thought I have ever put into white light.
     
  9. zac850

    zac850 Well-Known Member

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    Yes, the G stands for Gam.

    Last year, when I was designing Into The Woods, I had a light on Repunzles tower. In my plan I had it with no gel, because I wanted it white and "pure", as Repunzle is when she is in the tower. The lighting instructor suggested that I use this gel, so I decided to get a sheet of it.

    I must say I really like the color. It gives a hint of blue, but not that much, and gives a very nice, cool, white look on stage.
     
  10. JahJahwarrior

    JahJahwarrior Active Member

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    actualy, thinking about it, at this local ministry, they do a week long summer outreach, and they end it with a show. They did two weeks, this year, one week ended with SURGE, a teen-adult show, the other ended with Pizzazzle, a kids show. For the kid sshow, they put on a skit (ike, a 10 minute play) about this knight, and he rescues this girl from a tower, we used flats and he just goes behind a flat and climbs up the ladder she was on...I didn't have enough dimmer channels for the Leko I had shining in her window, so what I did was put a switch for it on the ladder. She climbs up, ,hits the switch, one more stepo up and she is in the window. worked VERY well! I used a blue that wasl ike that for her...it did give me a nice white light.....

    it just kinda depends...the play my schoool is doing now is probably going to use R61, "mist blue" and bastard amber for teh comedy we are doing. It has a little more blue, so it doesn't just look like white light, but it doesn't look like bluel ight. I guess I just like a little more blue in my light...but yeah, if you want a nice white, try G870, that seems like it would work pretty well when I think about it more, good suggestion Zac850!
     
  11. zac850

    zac850 Well-Known Member

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    Hehe, thanks

    Hum, light switch on stage, thats an idea. For the upcoming drama we are turning a small room into a thrust stage, and I am using instruments (S4 PAR's) from the larger space. Problem is, I don't have enough dimmers for all of the instruments I need to use. I have put in for new equipment (http://www.controlbooth.com/ftopict-1422.html), but, surprise surprise, the budget has disappeared.
     
  12. ship

    ship Senior Team Emeritus Premium Member

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    No I do mean Gam E as opposed to Gam G. I presume that Gam E is the Euro line of it. I have a conversion chart I have been working on for a while using conversion charts offered by Gam and Lee out of Stage Lighting Revealed and from a few other sources. These are the three gels that most approximately match up with Rosco #02 as asked about. The Gam is supposted to be slightly yellower and less pink than the Lee/Rosco but otherwise the Lee #162 and Rosco should be about the same.

    When talking about how white the white light is you are talking about color temperature. The whiteness of a incandescent household lamp 2,800°K on average at best for instance when compared to a 3,200°K stage lighting fixture - also on average, you note how white that light appears to be or in the color spectrum how close to the blue range it is.
     
  13. propmonkey

    propmonkey Well-Known Member

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    doe anyone use rosco 33(no color pink)? thats what we use all the time. its not as ahrd as white on the skin. in our little theatre he uses rosco 33 and rosco 60. i think i might try to use half and half for skin of our teeth, i know im going to be busy befoer the 3rd act dropping in gobos.
     
  14. JahJahwarrior

    JahJahwarrior Active Member

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    yeah, I know about color temperature...my problem is I always forget how it goes. Wamer colors are higher or lower temp? (ie: yellowish light, is wamrer light than blue light, blue light is cold, so it yellow higher temperature on the chart, or is blue? I always forget and I think it is backwards, so that warmer light (yellow) is colder temperature, but maybe that is just with teh sun...)

    in genreal, I dno't worry with getting perfect white light, I just leave them ungelled if I want white and I don't worry about if it is yellower than true white...I used a light blue gel not really to get a pure white, mainly to make it look like she was high up in a tower, and that gave me that effect, but looking back on it, it did look maybe more like pure white...

    thanks Ship for your advice so far, and can you please answer my color temp. question? thank you!
     
  15. zac850

    zac850 Well-Known Member

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    whiter light = higher color temperature
    amberish light = lower color temperature

    And if you take a bulb and dim it, you will get an amber shift to the amber side.
     
  16. ship

    ship Senior Team Emeritus Premium Member

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    A lot of these "words" I have written are written by others from my notes I have taken on stuff. Thanks in another posting about the credit, but I'm a tech person and disserve perhaps some credit but always need to have friends ensure what I'm doing is correct in making it safe for all. Nobody is a engineer or god, we all have both shortfalls and inperfections. Choice you have is allowing them to stay as a short fall, choice your friends have is in allowing those shortfalls to remain un-challenged.

    So here is more "words" in answering the question as others have written:
    (Read, study and learn as much as you can because in the end and in some respects what you even sort of remember will be all that stands in the way of a vague concept's success.)
    Almost none of this I have written more than some form of laymen's follow up to.



    Color Rendering = As a rule, artificial light should enable the human eye to perceive colors correctly, as it would in natural daylight. Obviously, this depends to some extent on the location and purpose for which light is required. The criterion here is the color rendering property of a light source. This is expressed as a “general color rendering index” (CRI). The color rendering index is a measure of the correspondence between the color of an object (its “selfluminous color”) and its appearance under a reference light source. To determine the CRI values, eight test colors defined in accordance with DIN 6169 are illuminated with the reference light source and the light source under test. The smaller the discrepance, the better the color rendering property of the lamp tested. A light source with a CRI value of 100 displays all colors exactly as they appear under the reference light source. The lower the CRI value, the poorer the colors are rendered. - Osram Photo-Optic Lighting Products, 1999
    Color Temperature = Originally, a term used to describe the “whiteness” of incandescent lamp light. Color temperature is directly related to the physical temperature of the filament in incandescent lamps so the Kelvin (absolute) temperature is used to describe color temperature. For discharge lamps where no hot filament is involved, the term “correlated color temperature” is used to indicate that the light appears “as if” the discharge lamp is operating at a giving color temperature. More recently, the term “chromaticity” has been used in place of color temperature. Chromacity is expressed either in Kelvins (K) or as “X” and “Y” coordinated on the CIE Standard Chrom-aticity Diagram. Although it may not seem sensible, a high color temperature (K) describes a visually cooler, bluer light source. Typical color temperatures are 2,800°K (incandescent), 3,000°K (halogen), 4,100°K (cool white or sp41 fluorescent), and 5,000°K (daylight-simulating fluorescent colors such as Chroma 50 and SPX 50.
    Unit of measurement: Kelvin (K) the color temperature os a light source is defined in comparison with a “black body radiator” and plotted on what is known as the “Planckian curve.” The higher the temperature of this “black body radiator” the greater the blue component in the spectrum and the smaller the red component. An incandescent lamp with a warm white light, for example, has a color temperature of 2,700°K, whereas a daylight has a color temperature of 6,000°K. - Osram Photo-Optic Lighting Products, 1999
    Light color = The light color of a lamp can be neatly defined in terms of color temperature. There are three main categories here: warm<3,300°K, intermediate 3,300 to 5,000°K, and daylight > 5,000°K. Despite having the same light color, lamps may have very different color rendering properties owing to the spectral composition of the light. - Osram Photo-Optic Lighting Products, 1999

    CRI = Color Rendering Index - An international system used to rate a lamp’s ability to render object colors. The higher the CRI (based upon a 0-100 scale,) the better colors appear. CRI ratings of various lamps may be compared, but a numerical comparison is only valid if the lamps are also rated for the same chromacity. (see Chromacity.) CRI differences among lamps are not usually significant (visible to the eye) unless the difference is more than 3-5 points.

    v = Volts - A measurement of the electromotive force in an electrical circuit or device expressed in volts. Voltage can be thought of as being analogous to the pressure in a waterline. The effect of voltage on a lamp will cause a significant change in lamp performance. For any particular lamp, light output varies by a factor of 3.6 times and life varies inversely by a factor of 12 times any percentage variation in supply. For every 1% change in supply voltage light output will rise by 3.6% and lamp life will be reduced by 12%. This applies to both DC and AC current. Most standard line voltage lamps are offered at 130v. Since most line voltage power is applied at 120volts, the result is a slight under voltaging of the filament. The effect of this is substantially enhanced lifehours, protection from voltage spikes and energy cost savings.
    Voltage and Light Output: The effect of voltage on the light output of a lamp is ±1% voltage over the rated amount stamped on the lamp, gives 3.1/2% more light or Lumens output but decreases the life by 13% and vise a versa.
    Do not operate quartz Projection lamps at over 110% of their design voltage as rupture might occur. GE Projection, Ibid p.13
    A 5% change in the voltage applied to the lamp results in
    -Halving or doubling the lamp life
    -a 15% change in luminous flux
    -an 8% change in power
    -a 3% change in current
    -a 2% change in color temperature (0.4% change per1% voltage.)
    Osram Technology and Application Tungsten halogen Low Voltage Lamps Photo Optics, p21

    There is more to know and other stuff I have in notes about the subject but this should be a good start. Pay especial attention to the effects of votage on color temperature, you will not find a figure of it's effects elsewhere but it's a key factor.
     
  17. ship

    ship Senior Team Emeritus Premium Member

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    Did some more work on converting one gel to another. RX 02 is like Roscolene 803, Lee 162, CineColor 602, Apollo 7050 and on the question of Gam E chart stands for Excellent match to Gam 340.
     

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