All About White Balancing - Sony PDX10 Workshop Handbook

APPENDIX A

ALL ABOUT WHITE BALANCING

Light bulbs, fluorescent tubes and the sun - we all see these sources of light as white light . But our
eyes are deceiving us, these sources of light vary considerably in their color. Our brains are very good
at performing a white balance without us really noticing. However the camera has to be told what type
of light it is working in - so that it can correctly reproduce what our eyes see.
To understand the need to white balance you first have to understand color temperature.
If I put a poker in a fire it will start to glow "red hot" - if I put it in a furnace and really heat it up it
will look as if it is "white hot". As the temperature of the poker rises the color of light it emits
changes. Red hot is pretty hot while white hot is very hot. There is a definite connection between the
temperature of the metal and the color of light it emits. This "color temperature" connection is a way
of scientifically quantifying the color of the light source.
Ok now think about a light bulb - inside is a filament (made of tungsten metal). When you switch on
the electricity, a large current flows through a small filament, it gets hot and starts to glow. The color
temperature of tungsten light usually lies at around 3,200 Kelvin. It is actually a reddish orange light.
The sun is another main source of light. As you'd expect it is hotter than a light bulb! The temp on the
surface of the sun is 5800°K and at its core, it reaches millions of degrees. However, the light that it
produces passes through its own atmosphere and the earth's atmosphere before it reaches earth's surface.
So, daylight consists of a mixture of the light that comes directly from the Sun with the indirect light
that comes from diffusion and reflection, caused by earth's atmosphere and clouds. This makes color
temperature on the ground pretty variable from as low as 2,000 Kelvin up to 20,000 Kelvin. The table
below shows the range of temperature possible for daylight and the conditions that effect it (along with
some other light sources).
LIGHTSOURCE & COLOR TEMPERATURE (Kelvins)
Candle 1,930
Sunlight at sunset 1,900 - 2,400
Domestic tungsten light bulbs 2,600 - 2,900
TVstudio tungsten lighting (2000 Watts) 3,275
TVstudio tungsten lighting (5000 Watts) 3,380
Sunrise, Sunset 2,000 -3,000
Fluorescent tube 4,800
Noonday sun 5,000 - 5,600
HMI and MSR lights 5600K
In shade ( light only from hazy sky) 7,500 - 8,400
In shade ( light only from Blue sky) 12,000 - 20,000
WHY IS WHITE BALANCING IMPORTANT?
Well, we have to tell the camera what color of light it is working in so that the picture it records looks
something similar to what our eyes see. To do this we need to do a white balance. When the camera
does a white balance - it analyzes the spectrum of colors hitting a white piece of
paper. It juggles these until the white looks white.
SONY PDX10 Handbook page 25