White balance and skin tones - part 1

Kathryn and white balance options - it makes a difference.

Light is made up of colours.  We know this from our experiences with things like prisms and rainbows.  We expect that light from any source can be broken up into its spectral components, and that those resulting spectrums should be equally balanced; that the amount of blues and greens and reds and all the infinite colours in between should be similarly proportioned.  After all, white light is white, isn't it?

The problem is that our eyes compensate for any colour shifts and what we see as white may actually not be.  For example, if you took a white sheet of paper and photographed it with the same white balance setting (say 5500° Kelvin) in a variety of settings, you would find that those resulting images would be different.  Even though that paper looks white to our eyes in those circumstances, it in fact is not.  This is because the light falling on it does not have an equal balance of all colours.

We know light from the sun is fairly evenly balanced, but that really depends on the time of day, the latitude, and the time of year.  When the sun is blocked by something and produces a shadow, you can still see inside that shadow.  It is not pitch black.  That is because light from the sky falls on that shaded area, allowing us to see.  That same sheet of paper would look fairly white in the sunny photograph but would look decidedly blue in the shaded one.  Take it indoors and photograph it under the old tungsten (incandescent) lights and it would look very yellow-orange.

The reason why these strange off colour balances occur is because the "white" light being produced has different amounts of the colours making it up.  For the shadow situation, there may be a lot of blue but little in the way of reds.  In the case of tungsten there will be a significant amount of yellows and oranges but little in the way of greens and blues.  Fluorescent tubes, CFLs, LED bulbs, mercury vapour bulbs, and so on all produce different shades of lighting because the balance of colours is not all the same.  We can say then that they have different white balances.

Most digital cameras have a white balance setting on them.  There is the fluorescent setting, the flash and tungsten setting, the outdoor and the shade setting, and maybe a few others.  Each one is preset to a particular white balance.  The problem is that those lighting situations are not necessarily exactly equal to what those white balance presets are.  Then there is the auto white balance setting.  The auto white balance feature lets the camera determine what white looks like.  The problem is that it is often wrong.  Sometimes it is off by a bit, other times it is off by a lot.

There are three great solutions for this.  I will go into this more on my next blog.  Thanks for reading.

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