Introduction to White Balance


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White Balance (WB) is an aspect of photography that many digital camera owners ignore or don’t understand but it’s something well worth learning about as it can have a real impact upon the shots you take.
White Balance is the process of removing unrealistic color casts, so that white portions of the shots are rendered white in your photo. Most of the digital cameras has the possibility of changing the setting of WB, also known as color temperature.

Why use of auto white balance is not advisable?

Depending on the scenario and object reppresented on the picture digital cameras have great difficulty with auto white balance (AWB), reason in most of the shoots you will
have a blue, orange or even green colour cast image.

What's the color temperature?

Considering an idealized physical body able to absorb all incident electromagnetic radiation (black-body), regardless of frequency or angle of incidence, the color
temperature of a light source is a characteristic of visible light that has important application in photography.
Color temperature is conventionally stated in the unit of absolute temperature, the Kelvin, having the unit symbol K.
Color temperatures over 5000K are called cool colors (bluish white), while lower color temperatures (2700–3000 K) are called warm colors (yellowish white through red).


Why is color temperature a useful description of light for photographers, if they never deal with true blackbodies?

Fortunately, light sources such as daylight and tungsten bulbs closely mimic the distribution of light created by blackbodies, although others such as fluorescent and most
commercial lighting depart from blackbodies significantly. Since photographers never use the term color temperature to refer to a true blackbody light source, the term is
implied to be a "correlated color temperature" with a similarly colored blackbody. The following table is a rule-of-thumb guide to the correlated color temperature of some
common light sources:

Color Temperature Light Source
1000-2000 K Candlelight
2500-3500 K Tungsten Bulb (household variety)
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

Since some light sources do not resemble blackbody radiators, white balance uses a second variable in addition to color temperature: the green-magenta shift. Adjusting the
green-magenta shift is often unnecessary under ordinary daylight, however fluorescent and other artificial lighting may require significant green-magenta adjustments to the
WB.

Fortunately, most digital cameras contain a variety of WB presets, so you do not have to deal with color temperature and green-magenta shift during the critical shot.
This is the suggested solution to get the correct WB while shooting in Jpg\Tiff format.

One of the advantages of shooting in RAW is that you may set the WB in post production, after the picture has been taken. Performing WB with a raw file is quick and easier,
since you can have a visible and instant feedback. You can either adjust the temperature and green-magenta sliders until color casts are removed, or you can simply click on a
neutral reference within the image.
I will talk about neutral reference and custom white balance in my next article. stay tuned!


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