How to Make Backgrounds White in Photo Editing Programs
Have you ever taken a picture in a room with white walls, uploaded it to your computer, only to see that the walls are suddenly now green or orange? This is the result of an inaccurate white balance setting. When using film, many photographers shoot 'charts', which could either be a grayscale card or a range of colors. The purpose of these charts is so the film developer can calibrate the colors correctly. Different sources of light have different color temperatures that affect the color of the light, by shooting charts or adjusting the color balance, you can control the color temperature's affect on color. In the current digital age, photographers use white balance controls. If you fail to adjust the white balance while shooting, you will still have some options available in post-production editing programs.
Setting White Balance
Most quality cameras, both still and video, have the ability to set white balance. It is important that something truly white is used, such as a piece of paper. I would recommend using more that one piece of paper to make sure the thin paper isn't transparent. Fix the paper on a wall, and then light it evenly, making sure there are no shadows. Fill the frame with the white paper and then set your white balance according whichever camera you are using. This process is merely telling your camera what is true white - your camera will compensate accordingly for all colors. If you feel intimidated, you can always put it on auto, but auto is far from perfect, and your colors will likely be skewed.
Fluorescents are evil to most photographers due to their discontinuous light spectrum, which negates any 'true' color temperature. If you can, replace all industrial fluorescents with 'full spectrum' fluorescents. The more you can correct on the set the better. You can also use colored gels; in this case 'minus green' (also called magenta) will take out the green from the lights. With a color temperature meter you can see how much green you need to take out. In either case, you also have the option to adjust it in post.
Working in Post
My girlfriend had an old digital camera without an independent white balance control. Her pictures were consistently green. Adobe Aperture for Mac's has a simple to use color temperature and tint controls. If your picture is too blue or orange, adjust the temperature, and if it is too green or magenta adjust the tint. Keep adjusting it until the white objects in the picture appear a true white. As you can see, adjusting the temperature and tint can drastically affect you picture.
Photoshop, and most other picture editing software, allows you to adjust the color balance (red/cyan, green/magenta and blue/yellow) for shadows, midtones and highlights. More than likely the white you are trying adjust will me in the shadows or midtones. If you have too much green then add some magenta, or if the background is too red then add more cyan. These color balancing controls work really well and can salvage many amateur photographs.
Even though computers are great, try getting the picture you want in your camera first. The adjustments in post you have to make, the clearer your photography will be.Popular P&S Cameras for High Quality Photos: