Andrew Talks Photography: Colour Temperature

If you struggle reading white on black…go here…

A short while ago this blog touched on the subject of white balance. Another aspect to successful photography is having some knowledge about colour temperature, or the characteristics of available light. What does that mean? Well, to put it simply, the environment in which you are taking photographs is not consistent in ambient temperature from area to area; or region to region; and, indeed, hour to hour. Colour temperature may change from a candle lit room to the bright outdoor light; from sunny day to overcast; from sunrise to noon: and this thermodynamic temperature is measured in Kelvin (K) units.

The origins of this lies with the physics of heat which suggests that when in when a hypothetical black body is heated it will radiate light across the spectrum as it hots up. Consider a metal being heated and moving through a process of becoming red hot, then yellow and, one presumes blue, before liquefaction. One may struggle with this, because what is happening in this process is a cooling of the colour as the heated body gets hotter. Thus the reds are considered warmer colours than blues.

Just to confuse one slightly more, digital camera colour temperature is not quite the same as pure colour temperature; it borrows from the principle, and considers only the range red to blue (green is missing). And this is not a recent development in photography. In the good old days of film photography one could acquire daylight balanced or say tungsten balanced films. These were all K rated according to where you intended doing your photography. Do not forget that light balancing filters and gels, used with flash attachments, are used to manipulate colour temperature, so this is nothing new.

Digital cameras use this same concept, but come with a versatile freedom; that is the ability to manipulate white balance to change colour temperature from one location to the next within minutes rather than being stuck with a whole roll of film in the wrong photo temperature zone. Thus, with digital photography, colour temperature is used interchangeably with white balance, which as you will recollect provides for the remapping of a camera’s colour values when considering the ambient colour temperature.

Now, how is this theory of any practical use to the photographer? Perhaps if we demonstrate a few physical values, which the wildlife photographic enthusiast should be familiar with, this will help. Give or take your latitude and prevailing weather conditions; ambient colour temperature approximates on the following scale:
• At sunset or sunrise: +/- 2,000K;
• one to two hours before sunset or after sunrise: +/- 3,500K;
• mid morning or afternoon it is probably in the region of +/- 4,300K; and
• at midday: +/- 5,800K (note: standard daylight is 5,200K, shade is 7,000K).

The more sophisticated digital cameras not only allow you to manipulate your camera’s white balance settings, but they also allow one to adjust the colour temperature more exactly (generally recommended for advanced users, but wide open for experimentation if you have a sense of adventure). Some cameras have an ‘Auto K’ feature too (equivalent to auto white balance AWB). Generally those who choose this route would be armed with a commercially available colour temperature meter, otherwise it is pure guesswork based on those averages outlined above, which rather suggests you stick to your white balance controls.

Now here comes the good bit: creativity. By working your camera’s colour temperature outside the average ambient light temperatures, one can create moods with the Kelvin scale settings, warming up images taken in cool ambient light or doing just the opposite. So the wildlife photographer may well utilise this to extend the golden hours from early morning and late afternoon into a larger part of the day, but not by much. Silhouetting at sunrise or sunset benefits from a boost in colour temperature and reddens the cast.

For most of us, simple camera white balance settings will suffice, and for those who are a little shy with technology or playing with your camera’s settings, one can adjust colour temperatures after the fact if you shoot in RAW. Most RAW converter software provides for this. Use the K setting technique in moderation and always remember to reset your camera to the standard 5,200K before packing your camera away.

One thought on “Andrew Talks Photography: Colour Temperature

  1. Good Morning Professor
    Good article, it answers why my pics are “up the creek”, I did not get the Kelvin right.
    Another reason to shoot in RAW, it gives one the opportunity to try a correct an otherwise cock up pic.
    How did we manage with the old Kadakchrome 25 ASA???????

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