2. Check the scan quality and tonal range.

Before making adjustments, 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.

The histogram also displays the overall distribution of shadows, midtones, and highlights to help you determine which tonal corrections are needed. (See Checking scan quality and tonal range (Photoshop).)