One of the side-effects of the digital revolution in the world of film making is that while a great number of people now have the resources to produce their own films, because they lack a formal film school education, they are often confused by some of the traditional film making jargon. This thread began when a member of the group was confused about a post on another message board that was loaded with film jargon. It evolved into a discussion of color temperature and lighting gel selection.
Post 1:
"General! I need an Inky with a quarter CTO and an opal over here -
stupid nickname that the gaffer is stuck with on this shoot/a small fresnel (lensed) light, roughly half the size of our tweenies, it would be about 3 inches across and probably 300 watts/CTO, or Color Temperature Orange, converts daylight to match Tungston lights (the lights we use). Quarter CTO has a Mired Shift of + 42 and converts 5500K daylight to 4500K. Used when slight correction is desired or when daylight is below 4000K. It is optically clear and allows 81% of the light to pass through it. It can also be used on a light when a slight warming effect is desired./ Opal, or Opal Frost is a white diffusion material that is put in front of the light to reduce it's intensity. An Inky with a 1/4CTO and Opal will emit a soft, barely perceptible glow. It's hardly worth the effort.
some black wrap and a C stand with a single to the left.
Black Wrap is that black aluminum foil we use/I hope you know what a C stand is by now/Single is a single diffusion net
Over there I need a tweenie with a half CTB and cut it with a 250
Tweenies are the medium-sized purple-painted lights with the lenses made by Mole Richardson/CTB or Color Temperature Blue converts Tungston to daylight (it's the reverse of CTO) It has a mired Shift of -68 and boosts 3200K sources to 4100K. It's a partial conversion to compensate for varying daylight conditions and voltage reduction, or to boost aging HMI lamps and yellowed soft lights. It allows 52% of the light to pass through it. It can also be used to cool down the look./a 250 is Lee Filters’ half white diffusion
and give me a C stand with a double and a flag to get rid of that camera flare."
Double is a double diffusion net, blocks twice the light of a single/a flag is a black cloth on a frame used to totally block light
Post 2:
I've never heard anyone on any set called "general". I guess this was an affectionate nickname the D.P. or gaffer had for a lighting tech s/he was talking to.
Like I said, it's a nickname, not a film term.
It's not "an" opal, nor "a" 250". Perhaps s/he actually said "some opal" and "some 250".
Not necessarily. Frequently used gels and diffusions are often mounted on frames, so they can be quickly put into place, just like a silk, net or flag. So the reference could be to a framed opal or 250. I've also referred to single sheets of gel this way, as in "Marshall, get me a CTB from the tube over there". So it very well could be "an opal" or "a 250". However I find it interesting that he refers to one by name and one by catalog number.
and give me a C stand with a double and a flag to get rid of that camera flare."
You'd only need a flag to eliminate a flare. A double (net or scrim) cuts the amount of light (twice as much as a single), but doesn't block it, which a flag does.
But if the flare is coming from a reflection, say off a picture or a window, knocking it down with a net would be an option.
By the way, a net is the more versatile -- if more cumbersome -- grip variation on a lighting tech's scrim. The net is sewn on a metal frame and usually mounted on a C-stand; a scrim is (usually) a circular screen-like item which is dropped into a holder in front of a light's filament or lens. Scrims reduce all of the light coming from the source (or, in the case of half-scrims, light coming from one half of the
source), whereas nets can be placed anywhere in front of the lighting unit to cut either part of all of the light in variable angles.
While they both achieve the same result, I prefer scrims to nets, as they are smaller and lighter, thus easier to transport, and metal, so they don't rip or burn like nets do. The only thing I like to use nets for is sunlight, although if I could figure out a way to scrim the sun. . . .
Finally, "opal" is less dense than "250", though they both soften and spread the light in different ways.
Because you asked for it, here's a complete list of all the diffusion materials made by Rosco (along with Lee filters they are the two big gel and diffusion companies) and their properties as listed on their website. 250 is actually a Lee catalog number. Rosco does not have a 250 in their catalog.
Roscolux Diffusion Filters
Roscolux #100: Frost
Frost. Changes ellipsoidal to fresnel beam pattern.
Roscolux #101: Light Frost
Offers softened beam.
Roscolux #102: Light Tough Frost
Changes ellipsoidal into flood or scoop.
Roscolux #103: Tough Frost
Has twin qualities of wide diffusion and warm center.
Roscolux #104: Tough Silk
Creates a slash of light for stretching light along stairs, tables, cycs, etc. Diffuses while maintaining compactness of beam.
Roscolux #105: Tough Spun
Good on scoops for cyc lighting.
Roscolux #106: Light Tough Spun
Removes lens shadows.
Roscolux #111: Tough Rolux
Densest diffusion of the series. Spreads the light almost 1800.
Roscolux #112: Opal Tough Frost
Lighter than 100-103. An excellent diffuser for HMI, CID and CSI sources softening the beam slightly while maintaining excellent transmission.
Roscolux #113: Matte Silk
Good for striplights and specials.
Roscolux #114: Hamburg Frost
A very light frost; good on followspots and PAR lamps.
Roscolux #115: Light Tough Rolux
Roscolux #116: Tough White Diffusion
A range of diffusion materials adapted from cinematography-used for softening the shadow of the beam while maintaining a relatively high color temperature because of the use of ultra-white pigments in the manufacturing process.
Roscolux #117: Tough 1/2 White Diffusion
A range of diffusion materials adapted from cinematography-used for softening the shadow of the beam while maintaining a relatively high color temperature because of the use of ultra-white pigments in the manufacturing process.
Roscolux #118: Tough 1/4 White Diffusion
A range of diffusion materials adapted from cinematography-used for softening the shadow of the beam while maintaining a relatively high color temperature because of the use of ultra-white pigments in the manufacturing process.
Roscolux #119: light Hamburg Frost
Lighter than 114. Recommended for followspots and slight diffuse focus for ellipsoldals.
Roscolux #120: Red Diffusion
Combine a color with Matte Diffusion. Aids in broad, even illumination of cycs and drops. (Trans.= 12%).
Roscolux #121: Blue Diffusion
Combine a color with Matte Diffusion. Aids in broad, even illumination of cycs and drops. (Trans.= 8%).
Roscolux #122: Green Diffusion
Combine a color with Matte Diffusion. Aids in broad, even illumination of cycs and drops. (Trans.= 13%).
Roscolux #124: Red Cyc Silk
Combine a color with 104 Tough Silk. (Trans.= 12%).
Roscolux #125: Blue Cyc Silk
Useful in border and striplights to prevent scalloping; helps illuminate cycs and drops. (Trans.= 8%).
Roscolux #126: Green Cyc Silk
Useful in border and striplights to prevent scalloping; helps illuminate cycs and drops. (Trans.= 13%).
Roscolux #127: Amber Cyc Silk
A secondary color combined with 104 Tough Silk. (Trans.= 32%).
Roscolux #160: Light Tough Silk
Retains the diffusion properties of 104 but with less light loss.
Roscolux #162: Light Opal
A lighter version on the popular 112 Opal Tough Frost.
Roscolux #163: Powder Frost
A good medium cosmetic diffuser.
POST #3
I'm still a bit unclear on the whole 1/4 1/2 thing for gels and diffusion, is that referring to size (1/4 of the light or something?) or to the level of the light changing properties (1/4 is less than 1/2 in terms of changing light quality)?
OK, lets use CTB (Color Temperature Blue) for an example. Here is the Rosco catalog for CTB:
Cinegel #3202: Full Blue (CTB)
Standard Tungsten to daylight correction. Boosts 3200°K to nominal 5500°K daylight. Deep-dyed base. (Mired shift = -131, Trans.= 36%, -1.5s).
Cinegel #3203: Three-Quarter Blue (3/4 CTB)
Boosts 3200°K sources to 4700°K. Used when a partial conversion is desired, or when daylight is below 5000°K. Deep-dyed base. (Mired shift = -100, Trans.= 41%, -1.3s).
Cinegel #3204: Half Blue (1/2 CTB)
Boosts 3200°K sources to 4100°K. A partial conversion to compensate for varying daylight conditions and voltage reduction, or to boost aging HMI lamps and yellowed soft lights. Deep-dyed base. (Mired shift = -68, Trans.= 52%, -0.9s).
Cinegel #3206: Third Blue (1/3 CTB)
Boosts 3200°K sources to 3800°K. A partial conversion to compensate for varying daylight conditions and voltage reduction, or to boost aging HMI lamps and yellowed soft lights. Deep-dyed base. (Mired shift = -49, Trans.= 64%, -0.6s).
Cinegel #3208: Quarter Blue (1/4 CTB)
Boosts 3200°K sources to 3500°K. A partial conversion to compensate for varying daylight conditions and voltage reduction, or to boost aging HMI lamps or household incandescent sources. Deep-dyed base. (Mired shift = -30, Trans.= 74%, -0.4s).
Cinegel #3216: Eighth Blue (1/8 CTB)
Boosts 3200°K sources to 3300°K. A partial conversion to compensate for varying daylight conditions and voltage reduction, or to boost aging HMI lamps or household incandescent sources. Deep-dyed base. (Mired shift = -12, Trans.= 81%, -0.3s).
Cinegel #3220: Double Blue (2 x CTB)
Boosts 2800°K sources to 10,000°K. An over correction filter designed for special applications. Deep-dyed base. (Mired shift = -260, Trans.= 10%, -3.3s).
There are two things to look at here. One is the Mired Shift. Mired is an acronym for Micro Reciprocal Degree, a measurement derived by dividing one million by the color temperature in Kelvin. For example 3200K is 313 mired (1,000,000 ÷ 3200) and 5700K is 175 mired (1,000,000 ÷ 5700). Therefore the filter needed to correct from studio incandescent to summer daylight is 137 mired and the reverse, from 5700K to 3200K, requires a -137 mired filter. A half gel has roughly half the shift of a full gel. (For more info on this, check out http://www.tvtechnology.com/features/let-there-belighting/f_let_there_be_lighting-07.07.04.shtml).
The second is the Trans, or transmission number. This is an indication of how much light the gel will allow to pass through it. While they aren't strictly proportional, because some light will always be blocked, a half gel will always allow more light than a full, but less than a quarter.
POST #4:
One thing I already discovered there (if not the intended result) is that -- in a pinch, of course -- we could combine a full CTB and a full CTO for a makeshift ND gel.
Theoretically, yes, but since all gels cost about the same, it's not really practical. And since we've got more ND than anything else at the moment, we probably wouldn't need to.
POST #5:
I have to put it into crude terms to understand it. Full CTB (aka "Blue") will make the light from a tungsten lamp be daylight balanced. Half blue will take it halfway there, quarter blue takes it a quarter of the way there, etc. CTO turns daylight-balanced light into tungsten- balanced light.
Now, you can use these halfs and quarters to get the light just perfect, but most of the time, you use them for purely aesthetic effect. For instance, EXT FRONT PORCH - NIGHT; on the lamp that is casting the light from outside, you'll likely use a half blue to mimic moonlight, and then, on the lamp that is casting the light from inside the house, put a quarter orange to represent a household bulb. (But
you usually need at least one light that reads as "white," other wise it looks weird.)
Also, using slightly different shades is also a way to deflatten an image. Let's say your key and fill light are about the same brightness, and for some reason you can't change the brightness of either of the lamps, so it's making the actor's face become totally flat. One way to get some gradation on their face to is make one of the lights a slightly different color. An eighth blue/orange can be just the trick.
So why is blue/orange sometimes called CTB/CTO? Because there is "Show
blue," etc, which won't mimic daylight, but could be used to represent, say, a blue neon sign. But, usually when you say "Full Orange", everyone knows your mean CTO.
“Show” gels are also called “Party” colors, because they are used by DJ and nightclubs to create a visual effect without regard to color temperature.
Also, daylight isn't always daylight. Sometimes to match sunlight late in the day, or early in the day, or when it's cloudy or smoggy, a fraction will come closer than a full. Same applies with lights, as the age of the bulb and the use of a dimmer will also change color temperature, so that's where the fractions are useful.