Darkroom Insights: Understanding Color Temperature in Photography
The light is changing here in Southern Ontario. Sun rise is a bit later each morning and sunset a little earlier.
You have probably heard the term "golden hour", if you have decided to look into the fundamentals of creating better photographs. [that one and "the rule of thirds" are probably #1 and #2 on the list of quick lessons for newcomers that writers and photographers are eager to tell you about]
If golden hour is a new phrase for you, it's simply the period of time around sunrise and sunset where the sun is casting beautiful golden light from it's place near the horizon. The reason why the color of this light is different from what you expect to see at mid-day is because the light is passing through more air [and all of the particles suspended in it] as it transits from the horizon to your eye. The atmosphere is working like an Instagram filter that increases in opacity/intensity as the sun rolls from high noon to dusk.
So what does this mean for your photos?
Light that has to travel through more atmospheric particles before reaching your sensor [or film] will be cooler on the Kelvin scale [the measure of thermal energy that starts at Absolute Zero] than light that beams down from directly overhead as it looses energy and scatters along the way. Sounds simple enough, right?
When we think of cooler colors, we think of things like ice and snow; cool blues and crisp whites. This is true, of course, but light sources with lower temperatures in nature actually cast low-energy, long wavelength light at the red end of the spectrum. High energy, "hot" light is at the blue end.
An easy way to make sense of it is to think about the spectrum of a candle flame. It is brightest at the wick; where the ionized gasses are most excited. As you move upward and away from the wick, the flame is cooler and the colors will be a familiar yellow and orange fading to red as you get further along the edge.
Cool, right? [or warm? wait - - which is it?]
When discussing color temperatures, context matters. If we are describing a pigment [as in paint or ink], then we say that orange and red are warm colors. They evoke feelings and conjure memories of warm things. The color of natural wood is often described as warm. So are the gold and auburn hues of an autumn scene painted in oil or water color.
Similarly, we say that blue shades are cool. Imagine a winter landscape with cobalt shadows and sparkling white highlights. The whole scene is cold and we recognize it by the colors used. Why, then, do we have a convention for naming color temperatures in our camera that is the inverse of the terms we use to describe what we visualize in print?
This is a matter of language - one lexicon for students of optics and radiant energy - and one for students of emotion and artistic interpretation. Congratulations to you, Insightful Photographer; you get to be both.
So - warm light has a low Kelvin value and cooler tones are produced by light with higher Kelvin values. The middle ground for natural, mid-day sunlight is around 5,500 degrees Kelvin.
Your DSLR camera is equipped with software that can measure and compensate for variations in the overall color temperature of your composition. If you want to go a step further, a quality light meter will pin it down for perfect studio results. By correcting your white balance, you are instructing the onboard computer to make white or neutral grey subject elements look white or neutral grey in the recorded image [neither warm, nor cool]. This will slide the color temperature left or right uniformly throughout your frame to the point where white is white. Here's the trick: neural pathways in the occipital lobes of your brain do this naturally when you take in a scene with your eyes.
Wanna know what I do?
I balance color temperature in camera so that my RAW [.NEF] file will have as much fidelity to my interpretation of a moment as possible. My visual cortex recognizes the difference between a pretty girl in a white dress and a pretty girl in a blue dress whether it's cloudy outside or not. I make a point to tell my camera which is which by managing the white balance properly and then making interpretive tonal adjustments in post-processing to create the image that my heart witnessed. [more on that another day]
By doing this, I get to work from an image that most closely resembles events in a neutral state and any deviations in color temperature are mine by careful choice.
I will leave you with this: Photography is a fascinating medium for exploring, documenting and expressing your relationship with the world around and within you. For the love of all that's pure and good, let's take it out of AUTO mode.
Got questions about white balance? Maybe you have some thoughts on creative uses of color temperature in your work. Post them in the comments section and lets get the conversation going!