Diffusion Gels?

Hey other tehie people! I got a question for anyone who knows:

What, exactly, do diffusion gels do?

I know they're different from regular color gels, but I have never been able to find out how. Anything you can give me would be appriciated, thanks!

Ben

"LD's: We blind actors"

 

Hi Ben,
Diffusion gels come in a variety of different density's and grains. They come in light frost to dense frost, to directional diffusers which spread light horizontally or vertically, to full tuff-spun-silks which seem more like fabric then a gel. Their use is to primarily soften and spread or diffuse the light source. They take away the harsh glare to lights that may cause an actor to squint, and they give an even field to lights so there is no "hot spot" but the light is evenly and softly distributed over the area. Used a lot in TV more then theater--most of the theatrical use for frosts and diffusers is to spread a light accross a cyc or soften a gel color to an set or to cover an actor...additionally the addition of frost without color can make an actor stand out in a special without appearing to be in a "spotlite". TV use is to evenly cover and spread the subject being filmed so that all areas are evenly lit. Different frosts do different, but similar, things depending on the light source. All are used to soften and evenly spread out light...

hope this answers your question..feel free to ask more.

-wolf

 

Thanks wolf, that answers my question.

Later
-Ben

 

Used to be an old trick to frosted gel. Add a bit of oil to it's center and it's going to fill in some of the diffusion surface that defracts the light. That way you can have both a direct and graphic center of the beam, and a diffused edge to it. I never tried it myself, but it's an interesting concept. Some how, I just can't make myself spray a frosted gel with WD-40 however. Something wrong with that concept.

Anyway, my favorite frosted gel, and it's a major shame it's long since discontinued, is Roscolux #107. Kind of a combination of #101 and #114 if I remember my colors, yet it was of a blue base color that acted like a color correction gel in correcting for amber shift, yet without that extra gel, allowed for a cooler temperature and more light to get thru. Too bad Rosco does not make it any longer however.

Still, on gel, Wolf's description is about right. Go to a Rosco, Lee or Gam website and check out the sections on frost for more details and drawings of what the beam will look like with each type. Otherwise, I can post a copy of Rosco Tech Notes "Using Light Diffusion Media" that is very useful in understanding what is going on from a period of time when such tech notes were published and helpful.

 

Sounds like everyone over in the states uses Rosco!

Im a personal fan of Rosco, but everyone out here tends to use Lee, I think because Rosco is just a fairly new product here, we dont have Gam or Apollo but had Cinelux or something until a few years back!

Lee is alright.... but i find its not worth it, as it burns out much much quicker than rosco, its an absolute rip off out here too, but i dont like normal Rosco Supergel or whatever... E+ Colour is my favorite!!

Is gel type just a personal thing or have you guys found that one of the lines tends to be better than the rest?

 

Each brand is different. I was raised on Rosco colors and thus have fairly well memorized their numbers to colors. Lee is the gel most designers and companies I know of use the most, but it's a mixture of the two brands with Gam thrown into the mix for special colors. I love what some of the Gam colors look like and have never had a problem with them burning up, but for the most part, it's all a Lee and Rosco market. The gam gel while seemingly made like Rosco gel seems to have an almost dichroic quality to it's output in being extra vibrant. Had I not so much Rosco and Lee, and were I starting from scratch, I would probably base my gel off the Gam line of colors.

Lee and Roscolux have and don't have their own problems. They are made differently, but both these days make a quality product. As far as quality, one brand is probably as good as another. Personally, I probably have just as much Lee as Rosco in my personal files. I go to Lee when I run out of Rosco.
I just use the Rosco stuff because I have memorized it had I been raised on Lee that's what I would know. Could be a college thing - Rosco might be catching the kids while they are young in an effort to keep them as customers.

I know of one designer that swares by his old Roscolene gel. What ever floats your boat buddie because that stuff like old style non-High Temp Lee gel is evil. I have a Rosco E-color swatch book around here somewhere, can't find it at the moment. Didn't notice anything special about it however, and I don't think many places are using it. Apollo and there are a few other companies making gel that should work just fine. Have not tried it yet.

 

Rosco is one of the most common gel here in the states. I have used Rosco, Gam and Lee extensively--and what Ship said--I like the vibrance and color saturation and durability of Gam a lot. Gam lasts a lot longer than Lee in my experiences.

-wolf

 

we use 1200 fresnels and par64's to do colour washes in the theatre and have found that Lee gel only lasts a month, if that in our colour washes, keeping in mind they are used about once a week unless we have a big seasoned show in. it has started to become very frustrating and I am currently changing it all over to rosco as i do believe it lasts longer and has better colour...

We dont have Gam outhere either... but im gonna try and get one of their swatchbooks haha ive got a collection of swatchbooks here

 

I have a ton of GAM swatches..same for Lee and Rosco...but give me a shout if you can't find one down under.

-wolf

 

Been a while for me on the subject of gel and I have long since forgotten the exact ways the gel is made or if it's still valid any more, but I thought I remember Lee having both high temp and normal gel. Wolf or anyone else, how about a refresher course in the differences in how the various brands make their gel.

Might want to ensure that you are using the high temp version of your Lee because that short of a duration is wrong. I believe that if I remember right, the low temp stuff will be only one side with a Matt finish and it should point out at that, but it's been a while for me. The high temp. stuff should be more like a Rosco gel in it's feel and look of both sides shiny. If high temp, it should not be burning up that fast, unless very saturated. If it's burning up really fast, you probably do not have the right gel. Rosco I believe also offers a high temp line. Perhaps that's what the E-Line is. That in addition to Cinegel from them.

Otherwise, if high temp. I would assume that you will probably have the same problems with the Rosco or Gam lines. You shouldn't, but since I don't do shows any more, I can't really say what steps if we gel them at all, we would do with 2Kw and 5Kw Fresnels. I expect we might be using heat shield, but it's also HT. Lee that I would expect.

I would recommend going with a heat shield gel in front of the color if swapping brands is still giving you problems. That's something that is going to absorb much of the IR/heat in the light beam. Lee and the rest offer it. Lee makes the second best stuff, the best heat shield comes from some company in California, but I would have to look it up at work as for who it is. We use it for our 5K Fresnel scrollers and 9-Light mole lights, and that's about it because it's like a buck per square inch. For other things the Lee gel is what others recommend. Subject was just discussed on Lighting Network a few weeks ago so it's fresh in memory.

Tips on heat shield is that the more space you can create between it and your gel, the better off you will be. In other words, at very least install the two in different gel frames. If possible, perhaps you can bolt the frames together with a 3/16" standoff between the two. Even better than that, if you are using barn doors, you can put the heat shield in the normal slot, and the gel frame in the barn door gel frame slot. Were these lekos, I would say test your bench focus - especially doing that paper technique to see where the focal point is.

Of a final note, if this is a more or less perminant production, Rosco and other companies sell dichroic filters and glass color filters for a price that will not wear out. Could be worth it as long as you use some screening to protect the audience.

 

I have checked temperature ratings etc. of the gels and colours we are using and they all match pefectly alright. This isnt the first time ive had troubles with Lee gels, after one show they tend to get pretty crispy around the centre where as it takes a few shows of running hard before the rosco starts to do this.

thanks for that wolf, ive emailed gam for "product brocheure request" so i will see what i get from that.

Gel is made by placing a coloured film inbetween two pieces of clear film. it is then fuesed together with extreme heat and weight. There is a line of gel that you are able to buy here that doesnt have the two protective films on it, it gives fantastic colours but burns out after one show, good for one off things!

 

"Gel is made by placing a coloured film inbetween two pieces of clear film. it is then fuesed together with extreme heat and weight." Sounds like a description of what I remember from Lee gel. Rosco and Gam are solid color.

As for the other, perhaps Roscolene or something of the Rosco/Gam manufacture type. As I remember, the two brands are made with differing techniques.

 

Yeah, Rosco feels like solid colour too...

Is Apollo Gel used widely over there, I got sent a swatch today and I quite liked what I saw....
Does anyone have a conversion table for their weird AP numbers to Lee or Rosco?

 

Found the info on heat sheild if anyone is interested.
Premier Stage Lighting (Theatrical Supplier, Heat Shield Supplier) http://www.premier-lighting.com/

Last time I bought it, it was $0.14 per square inch plus a cutting charge for my scrollers so that I would not be paying for the scraps that I could not use.

Good stuff, but expensive. Not a buck a inch but still not cheap.

 

We use Lee cuz its cheap. Unfortunately we have a great deal on economics, especially since the company I'm working for is starting out wth lights.

 

Lee seems to be making something like that now in the 700 series, I will see this week how it works.
720 Durham Daylight Frost Durham frost with daylight (Full CT Blue)