Colour of light

2 Apr

When thinking about the colour of light you have to know that light is a mixture of all the visible colours. When some component is missing, e.g. blue the light appears to be yellow/orange, in other words its complementary colour.

How does that affect us? When looking with the unarmed eye you have to be aware that there is a change in the light during the day as the brain works on it to make us see it as white. Of course during sunrise and sunset it is easy to see the differences. The camera on the other hand has not ability and you have to “tell her” what colour the light has, otherwise it would show the light as it is but not how we see it.

Luckily cameras have sensors that can adjust for that but sometimes that does not work, especially when you don’t have a white or grey object in the frame.

The colour of light in that context is called white balance and is measured in Kelvin. This temperature grading has historical reasons as the colour of glowing metal at different temperatures were used to standardize the colour. Red, yellow and then blue, the hotter it gets.

So, why is there a different colour during midday and dawn? Atmosphere scatter photons and the higher the frequency and energy of the photon the more it gets scattered. In other words blue gets scattered more than e.g. yellow. during midday light falls directly from the sun to the earth, standing high up in the sky. During dusk or dawn it has to pass through more atmosphere due to the angle at which it falls on the earth and with that more blue is scattered and all you see is yellowish.

Middle of the day, daylight setting

Middle of the day, daylight setting

Middle of the day, daylight setting. Bluish in the shade

Middle of the day, daylight setting. Bluish in the shade

Middle of the day but low sun due to the northern location. Yellow-orange colour

Middle of the day but low sun due to the northern location. Yellow-orange colour

More pictures and correction of the white balance can be found here from earlier in the course.

https://afraudi.wordpress.com/2012/10/10/colour-cast-ans-white-balance/

I have come to the conclusion that white balance is very individual and that a correct white balance is not automatically the most attractive one. Often we feel that a slightly warmer touch can be more pleasing when being outside and that you want a more bluish picture when being inside with artificial lighting. Problems come at the moment when you have a combination of natural and artificial light and of course when thinking that normal tungsten or fluorescent light does not really fit in the white balance scale as it has a different spectrum than daylight.

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