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In this article, we’ll cover three correlated topics related to the craft of lighting using gels.
First, the changing of light color from one temperature to another. Second, repairing light sources with too much green or magenta; and finally, adding color to lighting. Gels, also known as filters, are typically utilized to make those changes.
Gels are sheets of polyester dyed in particular colors. They were known as gels in the early days of theatrical illumination because they were made of colored gelatin dried into thin sheets.
Unfortunately, the cheapest theatrical gels are not ideal for a video or film shot because the gels tend to be placed near the light (and heat) source, and cheap gels can melt quickly. As a result, the gels used in video and the film industry are generally referred to as "tough" gels.
Many businesses provide excellent tough gels, the most well-known of which are:
Color conversion, color correction, and color effect gels are essential in video and film processes.
Color-conversion gels are meticulously made to convert one color temperature of light to another. Conversion gels developed around the two main categories for color temperature in video and film:
A "Color Temperature Blue" gel, or CTB gel, changes the color of a quartz incandescent instrument from yellowish-orange 3,200 K to bluish 5,600 K.
A "Color Temperature Orange" gel, or CTO, on the other hand, is designed to change sunlight to match a quartz light.
Considering we live in a less-than-ideal world where color temperatures vary greatly, these gels are available in various densities or strengths, often 1/4, 1/2, and complete.
It's crucial to understand how gels operate. Gels are optical filters that absorb specific wavelengths ( Colors waves ) while effortlessly passing others. For example, blue frequencies are transmitted by a CTB gel, while red, orange, and yellow frequencies are absorbed.
A gel helps by removing particular colors; contrary to popular belief, gels don't give color to the light. Gels are unable to add color. A gel will not add more color if the required frequency is not present in the light in the first place or if it is present in low amplitude. For example, parking lot sodium vapor lights emit only a narrow frequency of orangish light. It will absorb the orange and pass almost no light.
A typical use for color-conversion gels is when holding an interview indoors in front of a wide window. When the blue sunlight coming through the window is practically unavoidable, you can apply a full CTB gel on your incandescent instruments to match the color of the sunlight.
The only issue with this method is that a full CTB gel absorbs a lot of light--nearly two-thirds of the light output!
Alternatively, use a big sheet of CTO gel to the window to convert the bright sunshine to orange to match your incandescent instruments. Rosco and others provide big sheets of window gels for this purpose.
Color correction gels serve to adjust fluorescent lights that have too much green. Although cheap fluorescent tubes, especially older ones, have very little red and a high spike of green on the color spectrum, making people look quite sick on film.
How to correct this situation? You can employ a minus-green (magenta) gel over the light to absorb the extra green wavelengths. While the gel appears magenta, it does not add magenta to the light but removes green. Unfortunately, the resulting light will still be weak in magenta tones, so you must increase the magenta in the camera or post-production.
However, if you employ incandescent instruments with the adjusted "cool white" tubes in an office, the extra incandescent lights may appear excessively magenta. As a result, an extra-green gel is placed over the incandescent lamp to remove some magenta from its light output.
These gels are less commonly utilized now because many fluorescent lights have enhanced color rendering properties.
The ultimate purpose of color conversion and color correction gels is to produce light that the camera recognizes as white. Both gels are applied to the lights before the camera's manual white balance is set. If the light is appropriately balanced, the light on-camera image will be uniformly white rather than magenta, blue, orange, or green.
What if you would like to add some color to your images? Color-effect gels can help with this. These gels purposely color the light, either a bit (a touch of warm amber) or dramatically (a bright primary red or blue). It's essential to apply these gels to the light after the white balance has been set on the camera, or otherwise, the camera will struggle to make your color effect look white as well, messing up the lights that should look white.
Color effect gels are commonly used to set the mood, like in the original Star Trek series, or for special effects, such as imitating fire or the green light of a radar screen. Gaffers frequently refer to strong primary and secondary colors as "party color" gels.
Color conversion gels are often employed for color effects; add them once the white balance has been set. For instance, using a 1/2 CTO gel to indicate warm interior light or a 1/2 CTB gel to suggest light from a window is standard. Lighting designers will frequently use 1/4 CTO gels on lights to give a little warmth to the illumination. For night settings, blue hues are employed to imply moonlight.
The neutral-density filter is the gel's fellow. It is a "gray" gel that absorbs all frequencies equally. It works similarly to a camera's ND filter in that it reduces the light level without affecting the color of the light. Of course, you can dim the light through an electronic dimmer, but this will generally change the color toward orange as the light dims. A neutral-density gel can reduce light output without affecting the color.
There are other choices, such as scrims (screens that you insert into the gel holder) or nets (black cloth on a frame placed in front of the light), but neutral-density gels are an easy option to have, and they're easier to pack than large nets!
Gels are relevant in photography and are one of the most common resources used by Photography Directors and Photographers to get the look they want in their projects, as we can see.
We hope you have discovered the craft of lighting using gels with this article and devolve your abilities with filters.
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Gels are optical filters that absorb specific wavelengths of light while allowing others to pass through. They remove particular colors from the light rather than adding color to it.
Color conversion gels are designed to convert light color temperature from one type to another. They match the color of different light sources, such as incandescent indoor light and sunlight.
Neutral-density (ND) gels are gray filters that reduce the light level without affecting its color. They are used to dim the light output without altering its color balance.
Some well-known providers of gels include Great American Market (GAM), Lee Filters, and Rosco.