White Balance & Kelvin

White Balance

The white balance feature on a DSLR, whether you set it to auto or make your own choice, is to manage a property of light, known as the colour temperature. On your camera you will have the option to make various selections, such as: daylight, cloudy, shade, tungsten, fluorescent, flash, auto, K standing for Kelvin (which we discuss later) and also custom.

Choosing the wrong white balance setting, by accident, or as a creative choice, will make a distinct and very noticeable change to the look of the picture. If you select “Tungsten” as a white balance option, the image will appear noticeably blue. So how do we create an accurate white balance for our camera to use, and do we need to?

If you wish you can purchase various devices, grey cards etc. that can be photographed out in the landscape. Your camera then can evaluate the image you take and more accurately measure the white balance at that moment in time. This process would then be known as setting a custom white balance, and would be saved in your cameras memory.  I have a grey card and l have used it but realistically I choose not to.

If you do chose to go ahead and purchase a “Grey card” beware that there is a difference between an “18% grey card” (which is used for setting exposure) and a “Spectrally neutral grey card” (which is used for white balancing). A spectrally neutral object will reflect equal amounts of red, green, and blue (it doesn’t matter how much light it reflects so long as it reflects equal amounts)

My own choice therefore is auto whilst outdoors, as the white balance can be altered later in software packages if it becomes necessary, most of the time it does not.

Kelvin

Kelvin is used in the measurement of the colour temperature of light sources. The body of measurement indicates that with a black radiator, has a temperature below about 4000 K appears reddish whereas those above about 7500 K appear bluish. Colour temperature is very important in the field of photography, where a colour temperature of approximately 5600 K is required to match “daylight”. The Sun, for instance, has an effective temperature of approximately 5778 K.

In this table we compare the typical colour temperature against the light source it represents.

Colour Temperature Light Source
1000-2000 K  Candlelight
2500-3500 K  Tungsten Bulb (household bulb)
3000-4000 K  Sunrise/Sunset (clear sky)
4000-5000 K  Fluorescent Lamps
5000-5500 K  Electronic Flash
5000-6500 K  Daylight with Clear Sky (sun overhead)
6500-8000 K  Moderately Overcast Sky
9000-10000 K  Shade or Heavily Overcast Sky

So as you can see then white balance is extremely important and certainly if you have taken some pictures which have some unusual “colour casts” blues or oranges, it most certainly has been due to the wrong white balance selection.

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