Colour Calibration :: Before You Panic II :: Tonal & White Balance

Back in the HSL Luminosity Tint & Shade post, I suggested that luminosity has a big impact on how we judge colour. I also showed how getting a tonal balance in black and white tonal range first, then switching the colour back on can enhance the feeling of colour. There is another important tool to help your colour judgement in a photo and that is White Balance.

The Idea behind white balance is an adjustment to match the colour temperature of your light source, and this is achieve by either warming (usually adding magenta) or cooling (usually adding green) the overall colour rendition. Human vision automatically undertake these changes so we seldom notice the effect of different light sources. However cameras will record these colour cast and that often leads to an unnatural looking image. In the early days of colour film, specific film stocks where developed for different light sources (specifically incandescent and tungsten lights). You needed to use different film under different lights. Digital Photography has enable these adjust to be undereaten in the camera when it prepares the jpeg render of the image. Most DSLR & mirrorless cameras can be White Balance calibrated for given scenes and lighting conditions. RAW formats which record more details of the image and only carry out the white balance (so AWB or Auto White Balance is ok) to render the jpeg thumbnail embedded in the RAW format in camera. However the photographer is able to carry out white balance after the photo is de-mosaiced and re-rendered in postprocessing steps. White Balancing can also be used to remove colour cast created by strong reflections of highly coloured surface.

It is my experience all the software I have used, with a white balance feature, can do a reasonable job removing colour casts providing you pick a neutral grey tone (or White or 18% grey card) in your photo.  As discussed on the video above those packages that let you then copy the white balance adjustment across a number of photos, then let you take a reference image perhaps with a “white balance” card infront or held by your subject. make an adjustment and then copy that across the rest of that set of exposures.

There seems to be quiet a school of thought that you can not perform White Balance on a Jpeg files (including the video above) after it is captured, but my experience is if you have a reference shot of a suitable card (with a white or neutral grey patch) you can improve the reliable rendition of colour. The example below is a jpeg file straight from my Olympus OMD EM10iii camera, which I post processed in Picasa 3 (ie an old bit of software).

.

In the example above I have already adjusted the tone to get the the white on my test strip lighter then I used the white balance eyedropper and pointed to one of the two very light grey patches on my test card and clicked. That’s all that’s required. Note I haven’t had to use an expensive bit of specialist gear or customised colour profile.

It is my observation that it requires both Tonal and White Balance together to “clean up” colour in a photo.