Monday, April 27, 2015

PhotoEditingTools :: White Balance, When & Where

Colour correction, usually just called white balance these days, has been an issue since the earliest days of colour film. Some aspects even stretching back further into the martials used in the construction of black and films. Looking around current net explanations the need for colour compensation might be related to a technical limitation of colour film or modern digital sensor, actually the truth is they are pretty good at capturing the true light and they are getting better. The issue is the human eye (and yes a lot of this pre-processing is done at the back of the eye and on the way to the brain) is very good at accepting that a wide range of illumination is actually a “white” light source and reflection of it in the surroundings. This acceptance of what is supposed to be white is general subconscious and takes a very short time. Yet light sources (particularly artificial ones) can vary in strength and their colour profile, which can be measure on the Kelvin Scale (shown on the right), which actually an absolute measure, but it has been adopted in photography as a measure of colour temperature. These measure all very technical and somewhat theoretical but essentially different light sources emit light that corresponds to different hues (colours). A candle or tungsten globe seen in daylight will appear quiet yellow/orangish but in a room just illuminate by that light source our eyes will happily convey the image as if illuminated by a white light. The camera however will “correctly” capture the image a with distinct orangey bias. Objects that our eye saw a white will actually be orange and other colours will have excessive yellow and/or red tints. Thus the photo may look wrong.

Cambridge Colour  website has a great tutorial on the theory of colour compensation (aka white balance) as well as good practical advice, for those that want to investigate this deeper.

The best place to adjust white balance is in your camera, and this is an area you will need to consult your camera manual but most digital cameras, even the less expensive point & shoot ones will have a number of white balance options typically indicated by icons like those on the right. They normally cover a decent range of common lighting sources. What’s more AWB Automatic White Balance techniques have become very dependable in most modern cameras, so it is the obvious default setting. Older Camera phones might be the biggest exception here, particularly in low and/or artificial light. So it is worth looking at you camera settings on your phone. understanding the right setting and changing them as required could make a big difference to your low light photos taken with your phone

When It comes to RAW photos the white balance may not have to be set in your camera (ie just leave it on the default AWB) because there is usually enough information stored in the RAW file to allow the colour adjustment to be undertaken on the RAW image, Most RAW photo editors then allow the recalibration of the image to either a given Kelvin temperature, standard light sources or even a better estimate of the “as shoot” balance.

Having advised that AWB (Auto White Balance) is probably the best default I need to point out that there can still be situation that can confused the camera (ie an scene of dominantly warm or cool colours). Alternatively if you are always reaching for the warming slider trying setting your white balance to cloudy or shade.

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