Color is one of the major artistic tools we have to express emotion and mood with photography. Color information travels from the outer world into our eyes and then cameras. From there it travels to our computers where we adjust the color images on our screens for output to ink-jet prints, world wide web or lab prints. How color is viewed and captured and adjusted in each step of this journey is a very complicated technical story, perhaps one of the hardest things to really understand in all of photography.
I want to avoid all the details here and just cut to the chase on what you need to get your color right.
The color of light varies depending on its source. The sun radiates white light which is a continuous spectrum of all visible wave lengths of light. As these wave lengths are absorbed and reflected, they are separated out and we see them as color.
Warm and cool are one way of talking about color. The beginning and the end of the day have warmer light (yellow, orange, red) and the middle of the day is more cool light color (blue, purple, cyan). Shade is cooler, as is over cast days.
The Kelvin scale is a linear measurement of how red or blue a light source is.
Different light sources have a range of color, from warm to cool. Candle and tungsten light is very warm, strobe/flash/mid day direct light are
Digital cameras have several ways to compensate for these variations in color. We need to set the camera to render the color of light correctly so that there isn’t an unwanted color cast. For instance, a candle lit scene will have light from the far left side of the kelvin scale, a very warm light (see the scale above). Unless the camera is set correctly for color, a white subject in this light will have a warm color cast, making the white appear red/orange/yellow. When you have your camera set to capture in the jpeg format, one of your options for correct color is to set the white balance to match the color of your light source. Buried in the menu of your camera is a color/white balance section where you will find a number of icons, similar to the diagram below.
You want to match the icon to source of light you are shooting in. This will get you close to correct color, it’s not usually perfect, but a pretty good way to get correct color. Another option is auto white balance, which will have the camera make its best guess about what the correct color should be. Your camera may also have a custom white balance option. This may have the best color rendition, but has to be set with each situation. Look in your manual for how to set it. The best way to control color temperature in your images is to shoot in the RAW format, if your camera has it. I shoot with my camera set to RAW and the white balance set to auto white balance. I adjust the color in my computer where I have the most control. Most photo editing software has a white balance tool, usually an i-dropper that allows you to click on something white or black to neutralize and remove any color cast. For example, click on a white shirt that has turned yellow from a color cast and instantly you will have a white shirt again.
Photoshop is the most popular software for adjusting digital photographs, and widely considered the best. There are usually many free sites now where you can adjust you images online. In the links section I have several photo editing sites and software listed.