© Phillip Whitt 2020
P. WhittPractical Glimpsehttps://doi.org/10.1007/978-1-4842-6327-3_5

5. Enhancing, Correcting, and Working with Color

Phillip Whitt1 
(1)
Columbus, GA, USA
 

In this chapter, we’ll now learn about improving color images—both enhancing color and correcting color problems. We’ll also work with color by colorizing a grayscale (black-and-white image).

The topics covered in this chapter are

  • Tutorial 6: Correcting an unwanted color cast using Color Balance

  • The Color Temperature dialog

  • Tutorial 7: Correcting an image using Color Temperature

  • Tutorial 8: Restoring faded color using Levels

  • Tutorial 9: Restoring faded color using Auto White Balance

  • Tutorial 10: Turning a color image to sepia using Desaturate

  • Tutorial 11: Turning a color image to black and white using Mono Mixer

  • Tutorial 12: Colorizing a black-and-white photo

  • Chapter conclusion

Tutorial 6: Correcting a Color Shift Using Color Balance

The Color Balance dialog is often used to correct images with color casts—essentially, this means shifting from the excess of a specific color by offsetting it with its opposite (complementary color) to rebalance the image. Figure 5-1 shows the Color Balance dialog’s complementary color pairs—the more one color is increased, the more its opposite is subtracted (e.g., increasing red reduces cyan and vice versa).
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig1_HTML.jpg
Figure 5-1

The color pairs used by the Color Balance dialog

In this case, we’ll correct an image with a blue color cast by offsetting it using yellow (blue’s opposite). We’ll make separate adjustments in the shadows and the midtones.

Note

Not all color casts are necessarily undesirable. For example, taking a photograph in the evening before sunset may produce a golden or yellow color cast that lends an ideal mood for the image. Undesirable color casts are often a result of chemical changes in the photographic print over the years, or the camera’s settings (such as white balance) being improperly set.

  1. 1.

    Open the practice image Ch5_Blue_Color_Cast in Glimpse.

     
  2. 2.

    Create a duplicate of the background layer (Right-Click ➤ Duplicate Layer) and rename it (Work Layer, or something similar).

     
  3. 3.

    Launch the Color Balance dialog (Colors ➤ Color Balance)—by ticking the Split view option, a side-by-side view comparing the effect applied shown against the original is displayed.

     
  4. 4.
    As shown in Figure 5-2, make the following adjustments:

    • Click the Shadows button.

    • Deselect the Preserve Luminosity option (the X in the box will not appear).

    • Move the Yellow-Blue slider to the left until the value is –40.00 (or double-click in the slider and enter the new values using the keyboard).

    • Do not click OK yet.

     
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig2_HTML.jpg
Figure 5-2

Adjusting the Shadows Range in the Color Balance dialog

  1. 5.
    Now, we’ll make some adjustments in the midtone range (Figure 5-3).

    • Click the Midtones button.

    • Leave the Preserve Luminosity option deselected (the X in the box will not appear).

    • Move the Yellow-Blue slider to the left until the value is –25.00 (or double-click in the slider and enter the new values using the keyboard).

    • Click OK.

     
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig3_HTML.jpg
Figure 5-3

Adjusting the Midtones Range in the Color Balance dialog

  1. 6.

    The last thing to do is to slightly sharpen the image. Open the Unsharp Mask dialog (Filters ➤ Enhance ➤ Sharpen (Unsharp Mask)).

     
  2. 7.

    Set the Radius to 1.00, leaving Amount and Threshold at their default settings (Figure 5-4), then click OK.

     
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig4_HTML.jpg
Figure 5-4

Setting the Radius in the Unsharp Mask dialog

Figure 5-5 shows the before and after comparison. When done, you can save as an .XCF file if you want to keep the file, or simply close it out.
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig5_HTML.jpg
Figure 5-5

The before and after comparison

Tutorial 7: Correcting an Image Using Color Temperature

In this lesson, we’ll use the Color Temperature dialog to warm an image that has a cool color temperature that happened as a result of the camera’s white balance setting being improperly set.

Note

Measured in Kelvin, color temperature refers how warm or cool the lighting in an image is. In this tutorial, the image is warmed by increasing the temperature from 6500 to 11000.

  1. 1.

    Open the practice image Ch5_Cool_Temp in Glimpse.

     
  2. 2.

    Create a duplicate of the background layer (Right-Click ➤ Duplicate Layer) and rename it (Work Layer, or something similar).

     
  3. 3.

    Launch the Color Temperature dialog (Colors ➤ Color Temperature)—by ticking the Split view option, a side-by-side view comparing the effect applied shown against the original is displayed.

     
  4. 4.

    Set the Intended Temperature slider to 11000, and click OK when done (Figure 5-6). This gives the image a noticeably warmer look, correcting the image.

     
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig6_HTML.jpg
Figure 5-6

Set the Intended Temperature to 11000

  1. 5.

    The last thing to do is to slightly sharpen the image. Open the Unsharp Mask dialog (Filters ➤ Enhance ➤ Sharpen (Unsharp Mask)).

     
  2. 6.

    Set the Radius to 1.00, leaving Amount and Threshold at their default settings (Figure 5-7), then click OK.

    Note I zoomed in a great deal to show the subtle but noticeable difference that the Unsharp Mask filter made.

     
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig7_HTML.jpg
Figure 5-7

Setting the Radius in the Unsharp Mask dialog

Figure 5-8 shows the before and after comparison. When done, you can save as an .XCF file if you want to keep the file, or simply close it out.
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig8_HTML.jpg
Figure 5-8

The before and after comparison

The Color Temperature dialog also contains a selection of preset temperatures as shown in Figure 5-9.
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig9_HTML.jpg
Figure 5-9

The Color Temperature dialog presets

Tutorial 8: Restoring Faded Colors Using Levels

In the last chapter, we used Levels to improve the contrast of a dull black-and-white image.

In this tutorial, we’ll use Levels to remap the tonal information of each color channel to restore a faded color photo.
  1. 1.

    Open the practice image Ch5_Faded_Color in Glimpse.

     
  2. 2.

    Create a duplicate of the background layer (Right-Click ➤ Duplicate Layer) and rename it (Work Layer, or something similar).

     
  3. 3.

    Open the Levels dialog (Colors ➤ Levels).

     
  4. 4.

    Under the Channel setting, select Red—move the black slider to the right the numeric value is 68, then move the white slider to the left until the numeric value is 206 (Figure 5-10). Do not press the OK button yet.

     
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig10_HTML.jpg
Figure 5-10

Adjusting the Red Channel in Levels to the settings shown

  1. 5.

    Under the Channel setting, select Green—move the black slider to the right the numeric value is 58, then move the white slider to the left until the numeric value is 200 (Figure 5-11). Do not press the OK button yet.

     
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig11_HTML.jpg
Figure 5-11

Adjusting the Green Channel in Levels to the settings shown

  1. 6.

    Under the Channel setting, select Blue—move the black slider to the right the numeric value is 45, then move the white slider to the left until the numeric value is 175 (Figure 5-12). Press the OK button when finished.

     
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig12_HTML.jpg
Figure 5-12

Adjusting the Blue Channel in Levels to the settings shown

  1. 7.

    We can see the image looks much better, but it could stand a bit of sharpening. Open the Unsharp Mask dialog (Filters ➤ Enhance ➤ Sharpen (Unsharp Mask)).

     
  2. 8.

    Set the Radius to 2.00, leaving Amount and Threshold at their default settings (Figure 5-13), then click OK.

     
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig13_HTML.jpg
Figure 5-13

Setting the Radius to 2.00 in the Unsharp Mask dialog

Figure 5-14 shows the before and after comparison. When done, you can save as an .XCF file if you want to keep the file, or simply close it out.
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig14_HTML.jpg
Figure 5-14

The before and after comparison

Tutorial 9: Restoring Color Using Auto White Balance

If you’re processing a large batch of old photographs (such as old family photos), using Auto White Balance can be a time-saver, although the results may be hit or miss. The results may be satisfactory, but not perfect.

In this tutorial, we’ll use Auto White Balance to restore an old photo that not only has faded colors but color shifts (meaning the dyes in the photo have shifted from the original colors over time). In the process, the contrast will also be improved.
  1. 1.

    Open the practice image Ch5_White_Balance in Glimpse.

     
  2. 2.

    Create a duplicate of the background layer (Right-Click ➤ Duplicate Layer) and rename it (Work Layer, or something similar).

     
  3. 3.

    Initiate the Auto White Balance command as seen in Figure 5-15 (Colors ➤ Auto ➤ White Balance).

     
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig15_HTML.jpg
Figure 5-15

The Auto White Balance command

  1. 4.

    There’s an immediate improvement; the colors look much more natural and the contrast improved. However, there’s a loss of density that results from years of degradation, so we’ll restore some of it.

     
  2. 5.

    Create a duplicate of the Work Layer (Right-Click ➤ Duplicate Layer).

     
  3. 6.

    Change the Blend Mode from Normal to Multiply, then lower the layer’s opacity from to 35–40% (Figure 5-16).

     
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig16_HTML.jpg
Figure 5-16

Changing the Blend Mode to Multiply restores some of the lost density

  1. 7.

    Right-click the Work Layer Copy thumbnail, then select Merge Down.

     
  2. 8.

    The last thing to do is to slightly sharpen the image . Open the Unsharp Mask dialog (Filters ➤ Enhance ➤ Sharpen (Unsharp Mask)).

     
  3. 9.

    Set the Radius to 1.00, leaving Amount and Threshold at their default settings (Figure 5-17), then click OK.

     
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig17_HTML.jpg
Figure 5-17

Setting the Radius to 1.00 in the Unsharp Mask dialog

Figure 5-18 shows the before and after comparison. When done, you can save as an .XCF file if you want to keep the file, or simply close it out.
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig18_HTML.jpg
Figure 5-18

The before and after comparison

Tutorial 10: Turning a Color Image to Sepia Using Desaturate

If you want to recreate the old-fashioned look of sepia-toned photographs, it’s easy to do using Glimpse. This method can be used on both color and black-and-white photographs in the RGB color mode.
  1. 1.

    Open the practice image Ch5_Color_to_Sepia in Glimpse.

     
  2. 2.

    Create a duplicate of the background layer (Right-Click ➤ Duplicate Layer) and rename it (Work Layer, or something similar).

     
  3. 3.

    Open the Sepia dialog (Colors ➤ Desaturate ➤ Sepia)—by ticking the Split view option, a side-by-side view comparing the effect applied shown against the original is displayed.

     
  4. 4.

    For the full sepia effect, leave the Effect Strength at the default setting of 1.00 (Figure 5-19), then click the OK button.

     
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig19_HTML.jpg
Figure 5-19

Leaving at the default setting creates a full sepia effect

  1. 5.

    Now we’ll sharpen the image just a bit. Open the Unsharp Mask dialog (Filters ➤ Enhance ➤ Sharpen (Unsharp Mask)).

     
  2. 6.

    Set the Radius to 1.00, leaving Amount and Threshold at their default settings (Figure 5-20), then click OK.

     
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig20_HTML.jpg
Figure 5-20

Setting the Radius in the Unsharp Mask dialog

Figure 5-21 shows the before and after comparison. When done, you can save as an .XCF file if you want to keep the file, or simply close it out.
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig21_HTML.jpg
Figure 5-21

The before and after comparison

The strength of the sepia effect can be varied. As Figure 5-22 shows, some color can show through if desired.
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig22_HTML.jpg
Figure 5-22

The strength of the sepia effect can be varied

Note

A sepia effect can also be achieved by desaturating the image (removing the color) and using the Colorize dialog (Colors ➤ Colorize). By using the Hue, Saturation, and Lightness sliders, it’s possible to further customize the results.

Tutorial 11: Turning a Color Image to Black and White Using Mono Mixer

Glimpse makes it easy to convert a color image to black and white (grayscale, to be technically correct). Black and white gives an image a different “feel” than color. While you can just remove all of the color by turning the saturation level to zero, this doesn’t always produce the best results without additional editing. The Mono Mixer dialog offers a great deal of control to fine-tune the results.
  1. 1.

    Open the practice image Ch5_Color_to_Black_and_White in Glimpse.

     
  2. 2.

    Create a duplicate of the background layer (Right-Click ➤ Duplicate Layer) and rename it (Work Layer, or something similar).

     
  3. 3.

    Open the Mono Mixer dialog (Colors ➤ Components ➤ Mono Mixer)—by ticking the Split view option, a side-by-side view comparing the effect applied shown against the original is displayed (Figure 5-23).

     
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig23_HTML.jpg
Figure 5-23

The Mono Mixer dialog

  1. 4.

    The default settings yield good results, but we’ll make a couple of slight adjustments to create a little more contrast between the railroad ties and the grass growing between them.

     
  2. 5.

    As shown in Figure 5-24, adjust the Red Channel Multiplier to 0.75 and the Blue Channel Multiplier to 0.110—press OK when done.

     
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig24_HTML.jpg
Figure 5-24

Adjusting the Red and Blue Channel Multipliers

  1. 6.

    Now we’ll sharpen the image just a bit. Open the Unsharp Mask dialog (Filters ➤ Enhance ➤ Sharpen (Unsharp Mask)).

     
  2. 7.

    Set the Radius to 1.00, leaving Amount and Threshold at their default settings, then click OK.

     
Figure 5-25 shows the before and after comparison. When done, you can save as an .XCF file if you want to keep the file, or simply close it out.
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig25_HTML.jpg
Figure 5-25

The before and after comparison

The Desaturate Dialog

Another method of converting color images into black and white is to use the Desaturate dialog (Colors ➤ Desaturate ➤ Desaturate). Figure 5-26 shows us the navigation sequence (yes, the word Desaturate is shown twice).
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig26_HTML.jpg
Figure 5-26

Navigating to the Desaturate dialog

The Desaturate dialog offers five options: Luminance, Luma, Lightness (HSL), Average (HSI Intensity), and Value (HSV). Figure 5-27 shows the differences in tonal values. These values are based upon mathematical calculations which are explained in detail in the GIMP user manual: https://docs.gimp.org/2.10/en/gimp-filter-desaturate.html.
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig27_HTML.jpg
Figure 5-27

The different modes available in the Desaturate dialog

Tutorial 12: Colorizing a Black-and-White Photo

Glimpse is a great program for colorizing black-and-white images. In the early days of photography before color film was widely used, black-and-white (or toned monochrome) images were colorized by using translucent oil-based dyes to provide an overlay of color. This tutorial is more or less the digital equivalent (but without the mess and more realistic results).
  1. 1.

    Open the practice image Ch5_Colorize_Pendant in Glimpse.

     
  2. 2.

    Create a duplicate of the background layer (Right-Click ➤ Duplicate Layer) and rename it (Work Layer, or something similar).

     
  3. 3.

    Normally, we save this for last, but for this tutorial, we’ll sharpen the image just a bit at this point. Open the Unsharp Mask dialog (Filters ➤ Enhance ➤ Sharpen (Unsharp Mask)).

     
  4. 4.

    Set the Radius to 0.75, leaving Amount and Threshold at their default settings, then click OK.

     
  5. 5.

    Launch the New Layer dialog and create a new layer (Layer ➤ New Layer). This will be used to colorize the felt background under the pendant.

     
  6. 6.

    Name the layer Red Felt and change the blend mode to Multiply, then click OK. This blend mode will provide the felt a deep, rich scarlet/red color.

     
  7. 7.

    Launch the Color Selection dialog by clicking in the active foreground color swatch in the Toolbox.

     
  8. 8.

    Change the foreground color to 100% red by clicking and dragging to the upper-right corner as shown in Figure 5-28—press OK when done.

     
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig28_HTML.jpg
Figure 5-28

Change the foreground color to 100% red

  1. 9.

    Select the Paintbrush Tool (P) and choose a soft brush tip (Hardness 025). Change the diameter to about 15 pixels.

     
  2. 10.

    Paint an outline around the pendant.

     
  3. 11.

    Select the Fuzzy Select Tool (U). Change the Threshold to about 50, and click in an area just outside the outline (Figure 5-29). Make sure the selection is made on the layer named Red Felt.

     
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig29_HTML.jpg
Figure 5-29

Use the Fuzzy Select Tool to make a selection just outside of the outline around the pendant

  1. 12.

    Before applying color, let’s grow the selection a little to make sure the entire area is filled (Selection ➤ Grow). Enter a value of 5 pixels, then press OK when done (Figure 5-30).

     
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig30_HTML.jpg
Figure 5-30

Use the Grow Selection dialog to make sure the entire area will be filled

  1. 13.

    Fill the selected area with red (Edit ➤ Fill with FG Color), then deactivate the selection (Select ➤ None).

     
  2. 14.

    Duplicate the layer named Red Felt (Layer ➤ Duplicate), and change the blend mode to Overlay—reduce the opacity to 20%.

     
  3. 15.

    Launch the New Layer dialog and create a new layer (Layer ➤ New Layer). This will be used to colorize the pendant.

     
  4. 16.

    Name the layer Bronze and change the blend mode to HSL Color.

     
  5. 17.

    Launch the Color Selection dialog by clicking in the active foreground color swatch in the Toolbox.

     
  6. 18.

    Change the foreground color to a bronze color by entering these values: R-23.1, G-17.6, and B-9.0 (Figure 5-31).

     
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig31_HTML.jpg
Figure 5-31

Change the Foreground color to a bronze color using these values

  1. 19.

    Select the Paintbrush Tool (P) and choose a soft brush tip (Hardness 025). Apply the bronze color to the pendant, adjusting the brush size as needed.

     
  2. 20.

    Check your work by changing the blend mode to normal—the color will opaque and reveal any overlooked areas. Change the mode back to HLS Color when completely colorized.

     
  3. 21.

    Launch the New Layer dialog and create two new layers (Layer ➤ New Layer) for both the heart- and eye-shaped rhinestones; name one layer Heart and the other Eye.

     
  4. 22.

    Change the blend mode of the layer named Heart to HSL Color, and the layer named Eye to LCh Color.

     
  5. 23.

    Lower the opacity of each layer to 70% (this keeps the colors realistic looking and not overpowering).

     
  6. 24.

    Change the foreground color to a deep pink by entering these values: R-100, G-0, and B-41.6.

     
  7. 25.

    Select the Paintbrush Tool (P) and choose a soft brush tip (Hardness 025). Change the diameter to about 35 pixels, and apply the color in the heart-shaped rhinestone in the designated layer.

     
  8. 26.

    Change the foreground color to a light blue by entering these values: R-0, G-89.4, and B-100.

     
  9. 27.

    Select the Paintbrush Tool (P) and choose a soft brush tip (Hardness 025). Change the diameter to about 15–20 pixels, and apply the color in the eye-shaped rhinestone in the designated layer.

     
Figure 5-32 shows the before and after comparison. When done, you can save as an .XCF file if you want to keep the file, or simply close it out.
../images/495886_1_En_5_Chapter/495886_1_En_5_Fig32_HTML.jpg
Figure 5-32

The before and after comparison

Chapter Conclusion

This chapter provided several tutorials on correcting color issues, as well as being a little artistic with color.

Here are the main topics that were covered:

  • Correcting an unwanted color cast using Color Balance

  • The Color Temperature dialog

  • Correcting an image using Color Temperature

  • Restoring faded color using Levels

  • Restoring faded color using Auto White Balance

  • Turning a color image to sepia using Desaturate

  • Turning a color image to black and white using Mono Mixer

  • Colorizing a black-and-white photo

In the next chapter, we’ll look at modifying, retouching, and restoring damaged photos.

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