The color of images can be altered in a variety of ways. The color balance can be improved, colors and be faded in and out, and tones can be changed. Special effects, like sepia and grayscale can be added to an image.
Color Correction
Original Image
The original image lacks contrast and has lost cyan. The composite histogram shows the peak for the white shirt and dress near the 50% level.
Master channel whitepoint adjustment
Adjusting the whitepoint on the master channel restores the contrast to the image but does not change the pinkish color cast.
RGB channel whitepoint adjustment
Adjusting the whitepoints for each channel, red, green, blue, separately restores an accurate white to the image. The blue channel required the most contrast enhancement to restore its tonal range.
Custom correction
After setting the whitepoint the grass still has a blueish cast. Fortunately the Canon ScanGear program allows custom curve editing. The green level in the shadows has been increased to restore the grass color.
A little gamma correction sacrifices some of the detail in the white shirt and dress in order to bring some of the detail out of the shadows. The image was also sharpened with the unsharp mask filter.
A final custom curve increased some of the contrast in the shadows.
Before/After
Notes
- for extensive editing, scan at 2x the desired resolution and save as TIF.
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Color correction by the numbers:
- Highlight: RGB @ 4% (245/255)
- Neutral (gray): RGB equal
- Shadow: RGB @ 85-90% (35/255)
- Flesh tones:
245, 215, 190 light
215, 180, 165 mid
170, 115, 90 dark
- whenever possible, perform color correction with scanning software.
Related Links
- Color correction reference
- Scantips.com has some supporting information on color correction.