White Balance in Photo Retouching - Pros and Cons of Software Solutions

The first thing you want to take care of, when you set out to retouch your photos, is white balance. White balance refers to the color of the light and assumes that the ideal light color is white. Some shots, like sunset or candlelight, do not have white light, but in general an impression of white light is desirable.

Some use Photoshop's auto levels to set white balance, but that is not ideal, since auto levels merely sets the brightest pixels to white and the darkest pixels to black without looking at the midtones. But what if the brightest pixel in your photo is not white? Or what if you do not have pure black in the photo? (Most photos have black areas, but the brightest pixel is rarely pure white).

The midtones are the most important and to help set the midtones correctly one adds a grey card to the photo. A grey card is a sheet of cardboard or plastic colored an exact midtone neutral gray. Ideally one has three cards: a black, a gray and a white. Photoshop's levels adjustment panel has three eyedroppers for picking color: one for white, one for gray and one for black. By clicking the gray color picker on the gray card, one can set the midtones to neutral gray. One can of course only include a gray card in the photo if one intends later to crop it.

If one does not want a gray card in the picture, or if one does not have a gray card at hand, one can use specialized software that scans the image and calculates the color of the light and sets it to white. There are problems with such software: what if there are no neutral areas in the picture to calculate the color of the light from? Some software does not need a neutral in the image, but most do to get a good result.

If you work with RAW images, you will have discovered that the RAW converters usually come with a slider for color temperature, meaning a slider to adjust the image cool or warm. But what if the color of the light is greenish as when you have taken a picture in fluorescent light? The cool-warm slider is good for regular incandescent light, but not for fluorescent.

Color adjustment sliders are rarely good for correcting white balance, because the color adjustment will not just neutralize the gray card, but will also tone the photo in an undesirable way: often the blacks get colored or the whites, or both.

In short one needs some neutrals in an image to set white balance. A white wall or a sheet of white paper will do well; preferably a gray card for the midtones.