White balance correction is to correct the light in a picture to white. To do this you must have a neutral in the image like a gray card or a white wall. Software can correct white balance, but not all software solutions are equally good.
The first thing you want to address, when you begin to retouch your pictures, is white balance. White balance refers to the color of the light and assumes that the optimal light color is white. Some shots, like sunset or candlelight, do not have white light, but usually an impression of white light is good.
Some use Photoshop’s auto levels to set white balance, but that is not ideal, since auto levels just sets the brightest pixels to white and the darkest pixels to black without considering the mid tones. But what if the lightest pixel in your photo is not white? Or what if you do not have pure black in the photo? (Most pictures have black areas, but the brightest pixel is rarely pure white).
The mid tones are the most important and to help set the mid tones correctly one adds a grey card to the photo when taking the photo. A grey card is a flat piece of cardboard or plastic colored an exact mid tone neutral gray. Ideally one has three cards: a black, a gray and a white. Photoshop’s levels adjustment panel has three color pickers 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 mid tones to neutral gray. One can only include a gray card in the image if one intends later to crop the picture.
If one doesn’t want a gray card in the picture, or if one doesn’t have a gray card at hand, one can later use dedicated software that analyzes the image and finds the color of the light and sets it to white. There are problems with such applications: what if there are no neutral areas in the photo to deduct the color of the light from? Some applications do not need a neutral in the image, but most do to get a good result.
If you work with RAW images, you will have found that the RAW converters normally come with a control 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 correction controls are rarely good for correcting white balance, because the color adjustment will not just neutralize the gray card, but will also tone the picture in an undesirable way: usually 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 piece of white paper will do well; preferably also a gray card for the mid tones.
Find out more about Photoshop plugins
photoretouchingtips 