About correcting images

It may be necessary to correct the color and tone in an image for several reasons. The original photograph may have a color cast caused by using incorrect film or lighting. Or the scan may have been imperfect--scanners can introduce color casts or artifacts. Or the colors in your original art may be out of printable range.

Complete the following steps to correct the color balance and tonal range of an image:

Calibrate your monitor Use Adobe Gamma to calibrate your monitor. Otherwise, the image on your monitor may look very different from the same image when printed or when viewed on another monitor. (See  Calibrating your monitor.)

View all pixels View the image at 100% before making any color corrections. The accuracy of color corrections may vary if all the pixels in the image aren't visible.

Check the scan quality and tonal range Look at the image's histogram to evaluate whether the image has sufficient detail to produce high-quality output. The greater the range of values in the histogram, the greater the detail. Poor scans and photographs without much detail can be difficult if not impossible to correct. Too many color corrections can also result in a loss of pixel values and too little detail. (See Checking scan quality and tonal range.)

Adjust the tonal range Begin tonal corrections by adjusting the values of the extreme highlight and shadow pixels in the image, setting an overall tonal range that allows for the sharpest detail possible throughout the image. This process is known as setting the highlights and shadows or setting the white and black points. (See Adjusting tonal range.)

Setting the highlights and shadows typically redistributes the midtone pixels appropriately. When pixel values are concentrated at either end of the tonal range, however, you may need to adjust your midtones manually. It is not usually necessary to adjust midtones in images that already have a concentrated amount of midtone detail.

Adjust the color balance After correcting the tonal range, you can adjust the image's color balance to remove unwanted color casts or to correct oversaturated or undersaturated colors. (See Using the Color Cast command.)

Make other special color adjustments Once you have corrected the overall color balance of your image, you can make optional adjustments to enhance colors or produce special effects. (See  Applying special color effects to images.)

Sharpen the edges of the image As a final step, use the Unsharp Mask filter to sharpen the clarity of edges in the image. This step helps restore focus to images that have undergone resampling as a result of tonal adjustments. (See  Sharpening images.)

Making Color and Tonal Corrections > About correcting images