Posted on 09/12/2014 7:55:46 PM PDT by servo1969
The way we perceive color is greatly influenced by our cultural understanding. We all grew up learning that Fire is Hot and Ice is Cold. Therefor red and orange are warm colors while blue and cyan are cool colors.
This association in our mind is so strong that filmmakers can actually invoke a sense of temperature just by the color palette they use in their films.
Take for example Spike Lee’s 1989 film “Do the Right Thing”
The film beautifully photographed by Ernest Dickerson, is awash in yellows, oranges and reds invoking the heat of a long, hot day in the Bed Stuy (Bed sty) neighborhood of Brooklyn New York The urban cityscape is a vibrant community full of life – a diverse neighborhood where every one knows and accepts each other. But things are boiling up under the surface. Old hurts are being remembered. Tensions build like a pressure cooker. And things are about to explode.
Contrast it to the Coen Brothers’ 1996 film Fargo
Photographed by Roger Deakins, Fargo is dominated by blue and grey – even the white snowy exteriors cast cold bluish light so that weather itself mirrors William Macy’s character’s icy soul. Its constant reminder of the frozen landscape surrounding him and his inept henchmen.
Both these films utilize production design to accentuate hot and cold, but they also push the feeling of temperature using creative applications of white balance and color temperature.
When we talk about color temperature, we’re talking about the property of white light. White light is really a creation of our own minds – there’s no color white in the light spectrum. The color White confounded people for thousands of years. It took Isaac Newton in late 17th century finally demonstrated using a prism that white light was really a mixture of all other colors of light.
But precisely defining the proportion of different colors and tying that to temperature would have to wait till 1900 and Planck’s law.
Max Planck was a German physicist commissioned by German manufacturers to figure out the best temperature to heat the filament of light bulbs for maximum light and minimum electricity.
He tried to tackle the problem with contemporary theories but the equations just weren’t matching up with hits experimental data. That’s when he put forth what would later become Planck’s law which described the type of electromagnetic radiation generated by a theoretical black body at a given temperatures.
Let’s back up… You see, everything in the universe that has a temperature above absolute zero gives off some sort of electromagnetic radiation whether that’s infrared, visible light, ultra violet or x rays and everything between…. Even you and I give off radiation but it’s in the form of low energy infrared which we commonly call heat – that’s what IR Night Vision Goggles pick up.
As you increase the temperature of something, it will give off more and more heat or electromagnetic radiation, get it hot enough, it will start to glow – now it’s giving off radiation in the form of visible light. Continue raising the temperature, and it the glow will go through a very specific range of color which is mathematically described by Planck’s law.
This is what we mean when we talk about color temperature – its the color of white that would correlate with the color of light a theoretical black body at that particular temperature.
What was the temperature that Max Planck finally settled on as the ideal for light bulb. It was 3200K which is still with us today in the form of incandescent light. In the filmmaking world This number is also known as tungsten balanced.
The Sun’s surface temperature is around 5800K but Sunlight after being filtered through our atmosphere can range anywhere from a correlated 2800K at magic hour (sunrise/sunset) and even up to 6500k on an overcast day. For most applications 5600K, color of light on a clear midday, is what we mean by daylight balanced
These are two examples of light being created by hot objects where really the light is more of a by-product. How do you get lighting for film without all the heat?
The first alternative are fluorescent ights which uses a tube filled with mercury vapor and an inert gas. When electricity is passed through, alternating very quickly, the gas becomes a plasma and gives off UV radiation. The UV radiation strikes the walls of the tube which are coated in phosphors and the tube begins to fluoresce and give off light. So instead of heat, it’s the glow of the excited phosphors and the mercury gas that’s generating light.
But unlike an incandescent bulb that gives off light in all frequencies according to Planck’s law Fluorescent bulbs tend to spike only at certain frequencies, mainly at the primary colors Red, Green and Blue. Red and Blue are colors created by the phosphors in the tube and green is created by the light emission of mercury. For cheaper bulbs, manufacturers will sometimes increase the amount of green because it gives the bulb a brighter appearance being that green is right in the middle of the visible spectrum. Unfortunately this can give footage shot under cheap fluorescent lighting a green tinge.
For photography and cinematography uses, manufactures mix different chemicals into the phosphors to get a fuller spectrum of colors as well as to alter the correlated color temperature so you can get tungsten balanced and daylight balanced fluorescent bulb. To get a more full spectrum, look for bulbs that have a higher Color Rendering Index or CRI. A CRI of 100 is full spectrum like the sun- for the best results use bulbs rated 90 or higher.
LED lighting is the newest alternative to incandescent lighting but they also can present many of the same issues as Flourscent lights when it comes to limited spectrum. The color of an LED is based on material used in the diode of the Light Emiting diode. There are several ways to get white light, either by using phosphors or by blending different colored LEDs together in a single fixture. Some fixtues even have the ability to dial in your color temperature by mixing the intensity of different colored LEDs.
There are traditionally two important numbers you should know by heart: 3200K which is the temperature of tungsten lighting and 5600K which is the temperature of sunlight at midday.
Almost all cameras have the ability to set a custom white balance using a grey card or white card. This is done by filling the frame with something gray or white and pressing the white balance button which zeroes the values so that color neutral.
For much better control, professional cameras also have the ability to dial in a specific number for your white balance. This is great for dialing in your look – if you want more of a warmer tone, push the color temperature higher, more cool, push the temperature lower.
And If you’re shooting with a camera that shoots in RAW format, you can save your white balance decisions until post.
A common color temperature problem that pops up is when you have competing light sources with different color temperatures – like you’re shooting indoors near a window and using tungsten light.
If you white balance to 5600K, the indoor lights will look orange. If you balance to 3200K, the light from the window will look blue. To get them to match you can use gels – either cover the entire window with CTO (orange) gel or just cover the light with CTB gel.
Corrected with CTB on light and camera set to 5600K
Of course there’s no reason why you can’t use that disparity for artistic effect.
It’s also worth mentioning here that the dimming of tungsten lights will lower their color temperature and make them look warmer. After all, the filament isn’t getting the same current therefore it’s not burning as hotly so by Planck’s law, they will be a lower color temperature.
Now there’s no need to adhere rigidly to any of these numbers. Just because we’re shooting under tungsten lighting doesn’t mean we have to set the camera to 3200K. Or that we can’t blend different color temperatures in a single shot and mix cold outdoor light with warm interior light. But understanding the mechanism of color temperature will help you solve artistic challenges when you’re on set. These tools go way back – from our earliest moments huddled around a warm life giving camp fire to Isaac Newton messing around with pieces of glass to Max Planck trying to figure how hot a light bulb should burn and founding the basic tenets of quantum mechanics in the process: each step furthers our understand and history – so use it and make something great.
Blade Runner just starting on BBC America. A true masterpiece of film making.
P.S. There is no green hot. Otherwise the temperature trajectory through the chromaticity diagram would pass through greens, but it doesn’t.
Even though a pure tungsten filament doesn't emit a black body spectrum directly from its surface, incandescent bulb filaments were designed to more closely approach the black body emission curve by being made as a "coiled coil," a very fine wire, wound into a very fine coil, with this fine coil itself coiled into a larger coil. In this way, each "surface element" of the filament was caused to "see" many other surface elements of itself; the bouncing back and forth of the average photon between these different surfaces caused some absorption and re-emission.
It is this equilibrium between absorbed and re-emitted photons that gives the beautiful black-body characteristic, similar to that generated by the hot carbon particles in a candle flame or wood fire.
Sunlight also is a fairly good approximation of a black body, albeit at something like 6500° K. I very much dislike LED and CF lamps. These (in effect) give "pixel color," meaning that they try to approximate natural light by combining light various fairly narrow wavelength bands. LEDs are worse than CF lamps because LEDs generate very narrow "spectral lines."
Thus, we are seeing a transition to what might be called "digital light" to go with the recent transition to "digital images" and "digital audio."
Here, the word "recent" means "over the past 30 years or so."
I believe that the human eye is not well adapted to "digital light." That's why sunlight - and light from incandescent light bulbs - is so pleasant.
In my basement, I have enough old fashioned 60W bulbs to last the rest of my life.
Interesting. Thanks.
Blue is the Warmest Color: the film for lesbians, color scientists familiar with Planck's curve, and especially lesbian color scientists. :-)
Except for astronomers. Blue stars are hot. Red stars are cool. There are no green stars.
ping for am coffee reading
I think we agree, but I don’t understand your comment about astronomers.
I’m a photographer, it seems like half my life is spent tweaking color temperatures/white balances. . . although, objectively it can’t be that much because then I wouldn’t have enough time for all the dust spot removal I do.
Most people seem to be under the mistaken impression that I get to all my time playing around behind a camera, my how I wish that were true.
It will be interesting to me to see how a discussion of color temperatures and white balance on a political forum unfolds.
Blue is hot and red is cool. It is the opposite to the way people “think” colors should be.
http://www.universetoday.com/24596/what-is-the-hottest-star/
Ordinary incandescents do have an advantage in that they are (mostly) full spectrum light, however, since I got into photography always find them too orange and dimmer than they should be. Somehow (as I gained the ability to gauge color temperature) my brain has lost it’s ability for my brain to adapt to the color temperature of ordinary tungsten bulbs.
Daylight balance bulbs are still too “cold” for my tastes (ironically higher temperature is more bluish and is perceived as being colder), but I really love those halogen bulbs they put in the form factor of a standard bulb. The light from those is just wonderful, ironically they never would have been put on the market if it wasn’t for the government sticking it’s nose into everybody’s lives. . . so I just have look at it as the private sector finding clever solutions to find their way around odious regulations.
Unfortunately, the wiring in my home is terrible and causes any kind of incandescent bulbs to burn out frequently, so I use the halogens to light my photographs and use LEDs in all the hard to reach places, which are common because I live in a home with cathedral ceilings in half the rooms. I don’t mind LED too much, but I definitely notice certain colors don’t look as vibrant as they should because they emit discrete frequencies of light. Reds in particular, appear duller.
Now CFLs, I don’t think you could pay me enough to have one of those in my home. Whomever came up with that garbage should be hanged, along with the politicians that attempted to foist them on the nation.
John Boorman used colored gels to set mood magnificently.
Reg giants are dying but red dwarfs are practically eternal.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.