The Basic Steps
Use the following set of steps to apply basic color correction to your images. These steps apply to any photographic image.
Open your image, and convert to RGB if it is not already in that color mode.
Do not attempt to do this in CMYK or other color modesthe results are not nearly so predictable.
Open the Levels function (Cmd-L)[CTRL+L].
- Switch to the Red channel by using either the popup menu or key commands (Cmd-1)[CTRL+1].
Using the sliders, crop the histogram.
You may want to use the Eyedropper or Auto options to help you with this selection and correction. To do it manually, move the right and left slider in to the edge of the solid area that registers on the graph (see Figure 1).
Repeat step 4 for the Green (Cmd-2)[CTRL+2] and Blue (Cmd-3)[CTRL+3] channels.
Return to the composite RGB level, and observe the effect of the changes.
If the image needs to be lightened or darkened, do so using the middle slider. If you are not sure, test by running the slider arrow between 120 and 80 (shown in the middle value at the top of the dialog box), and make a visual assessment of the changes. See Figure 2.
If everything looks OK, save the image.
If additional correction is needed, continue to work on the image color using other techniques (Color Balance, Variations, Eyedropper checking, Selective Color changes, and Curves).
Move the sliders in to crop the histogram and redefine the tonal range.
Here, the middle slider is at 120 (left of its original position at 100). This will effectively lighten the image overall because as the value of the middle slider increases, the amount of image information that falls into the brighter range also increases (more levels of tone fall into the right hand, or bright side, of the slider).