Has someone ever said to you, “I don’t like the LED look”? Depending on who you were talking to, you may have brushed that off, or really started to wonder what they meant.
Using different types of light is probably the most complicated variable in cinematography. This isn’t because you have to match Kelvin— it’s because each light that you use has slight changes in color, and color rendering. These small changes might not be instantly perceptible by your eye, but when you break apart light with a 4:2:0 capture and then stretch the contrast in post, you’re likely \LED’s, still in their infancy, present a variety of color matching issues when mixing sources or trying to match daylight. Because of this, it’s incredibly important to understand how light interacts with your subject. IndieCinemaAcademy.com has put together a comprehensive, and free analysis on the complexities of bi-color LED lights.
A lot of this may seem like technical information that doesn’t apply to a person that just goes out and lights up a space that you’ve never seen before. We’re all run and gun shooters of some kind, so what does it matter?
One of the most important elements of cinematography that seem to be lost on the modern digital videographer is understanding quality of light. It’s the understanding that a source isn’t defined just by its Kelvin. Once you begin to see lights as more complex fixtures, you’ll be able to get that perfect light match and correct for whatever is thrown your way. And if you read this incredibly detailed analysis from IndieCinemaAcademy.com, you’ll be able (or at least start) to use your LEDs to their fullest extent.
Complexities of Bicolor LED Lights: An Extensive Color Analysis
Via Indie Cinema Academy:
LEDs come in all types of shapes and sizes. There are panels, bulbs, ribbons, and COB (“chip on board”) fixtures often found in fresnel type point-source lights. For a long time these LEDs were single-color, balanced to either tungsten or daylight. However this year as we tested over 165 LED lights at the annual NAB trade show to update our comprehensive LED database, we found that over half of the LEDs at the show were bicolor. This was an incredible change from last year when there were only a handful.
What is a Bicolor LED?
The idea behind bicolor LED lights is that there are tungsten balance LEDs and daylight balanced LEDs mixed within the same fixture. By adjusting the intensity of each type of emitter, the entire range of color temperature spectrum between the two LED classes is now available to the filmmaker. This way a filmmaker just needs one type of light that they can dial in to match incandescent practicals, or the sun outside, or brands of single-color lights that have color temps that are a bit off, etc.
Initially this sounds like a wonderful idea, which is probably why so many LED manufacturers are doing it. They already have each type of LED, all they have to do now is repackage them into the same fixture and allow the user to dim them independently. Some manufacturers even provide a readout so you know where on the color temperature range the you are. (Word of caution: most of these readouts are off by 200 K and often even more.)
The more I thought about the intricacies of creating a bicolor LED, the more I wondered if this was even good for film and video makers. Mixing two dissimilar lights does not necessarily create a useful blended light.
Tungsten LED? Daylight LED? Please Explain
Tungsten light is based on blackbody principles, where a blackbody emits visible light if you heat it up enough. As it gets hotter and hotter, the color balance of the light changes, going from a more orange color to a more blue color. This is where the idea of correlated color temperature (CCT) come from, and why the units are kelvin (K), which is a measure of temperature. Looking at the spectrum from a true tungsten light source shows how full and even the color spectrum is.
However, daylight is VERY different. While the sun is a great light source, that light is significantly changed as it goes through our atmosphere. It’s why the sky is blue, the clouds are white, and the sunsets are so full of reds and oranges. This explains why the color temperature of daylight depends on time of day and if you are in the sunlight or in the shade, and if it is cloudy or completely sunny.
In fact tungsten light and “daylight” are so different that the color quality is measured using very different standards. These standards — called “standard illuminants” — abruptly change at 5000K, which is why all spectrometers give very odd graphics and data as you cross over this temperature point; below 5000K CIE Standard Illuminant A is used, at and above 5000K CIE Standard Illuminant D65 is used. (More on the abrupt change below, in the section titled “Specific R-Values.”)
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(cover photo credit: snap from Indie Cinema Academy)