Life is a long quiet river…

“Life is a long quiet river” is the poetic title of a 1998 French comedy  (La vie est un long fleuve tranquil). Somehow that seems to fit what I do – working with cameras and fishing for light. No dramas as such. The sun comes up and goes down every day, the light meanders, and I am a spectator watching the ebbs and flows.

For most photography, exposure and the colour of light are adjusted automatically by the cameras (and cell phones) of today which do an amazing job. But in our profession we need to understand a little of what is going on.

Take electric light for example. In the early days, the warm glow produced by a hot filament was quickly preferred to the blueish light of the gas lamps. But since then, bulbs have been created to satisfy all kinds of needs: to add ambience, to set the mood, to help plants grow, to control the light for precision colour matching. We work with light, we need to understand how colour temperature affects what we see.

Measuring the different colours of light

The colour of light is measured in degrees Kelvin, a thermometric scale invented by Lord Kelvin (1824-1907), ranging (for our purposes) from 1,000K to 12,000K or so. Simply put, it means the higher the K reading is, the whiter or bluer the image will be. Similarly the lower the degrees on the K scale, the yellower or redder the light will be.

For example, the standard, incandescent tungsten bulbs everyone uses in their homes (or used to) burn with a yellow/orange light from 2,700–3,300K. It corresponds to a soft welcoming colour, flattering like sunlight in the late afternoon. The red/orange of candlelight is warmer still at around 1,700K. And the colour of the flames in a wood fire might be as hot as 1500K or hotter.

In video production, we sometimes use Halogen lights although the bulbs get burning hot and use a lot of power, and the light they produce  is a warmish 3,200K. However over the last few years fluorescent tubes have been used in video because they give off very little heat, use less power and provide a soft, even light. And they are now available at two different colour temperatures from a warm 3,200K to a coolish 5,500K (N.B. only those marked with a CRI (colour Rendition Index) close to 100). As for photographers’ strobes, studio flashes are rated at 5,500K, close to the 5,600K temperature of sunlight light at midday.

Coloured gels can be used to balance the light, but it seems as if LED (Light Emitting Diodes) lights really are the future. They are inexpensive, portable and use little power. and unlike old-fashioned bulbs, they don’t have a filament to burn out since they shine through the movement of electrons in a semiconductor. And LEDS can be temperature matched and some are even temperature variable. 

However, if you have really deep pockets, and don’t care how hot lights get, how much power they use or how large they are, the best way to light a studio is still with mercury vapor HMI lights, high power medium arc-length lamps made specifically for the film and entertainment industries. 

The bottom line, is that even if your camera will do much of the work for you, understanding the colour of light is fundamental to film-making and photography – and there is still a place for colour temperature meters and light meters to help judge exposure.

 
The color of light

The color of light

I took both of these photographs at dawn in Moscow, in Red Square and behind St Basil’s Cathedral, and they both show how attractive early morning light can be – and many of the best travel pictures are taken at the golden hours of sunrise and sunset.

We tend to think of the color of light as white, or even colorless. Yet Isaac Newton himself (well-known as a scientist, but also an alchemist, magician and devout Christian) taught us that when light is white, it is actually made up of a “spectrum” of seven different colors; red, orange, yellow, green, blue, indigo, and violet. Seven colors because he believed light was governed by the same ratios as music (the diatonic scale) and time (the seven days of the week).

Today we’ve reduced those seven colors to three for the receptors in our eyes, each sensitive to a different range of visible light: red, blue, or green. RGB. Mixing those three colors creates the hues that we see.

However, we don’t see all three colors equally well. We are less sensitive to blue, more sensitive to red and very sensitive to green and yellow. Our brains compensate for the blue light at midday and the warm evening and morning light, so we hardly notice the color of light changing throughout the day as the sun crosses the sky – unless we get up at dawn to take a photograph.

In photography and video, modern cameras use the same RGB principle – but when blue midday light is coming through a window into a room filled with warm electric light the result is unnatural and unattractive. Which is where the Gaffer comes in, or the CLT (Chief Lighting Technician).

By measuring the color of light in the Kelvin temperature scale, the Gaffer will balance the light with coloured gels on the windows and on the lights, adding filters to the camera lenses to correct the unmatched light sources.

Even today’s advanced cameras will do much of the work for you, understanding the color of light is still fundamental to film-making and photography – and there is still a place for color temperature meters and light meters to get the exposure right.