Using Blend Modes in Photoshop-- Part IV

Article and Photography by Ron Bigelow

www.ronbigelow.com

Photoshop CS or Photoshop CS2 Used in this Tutorial

Difference Blend Mode

In each channel, the Difference Blend mode subtracts the blend color from the base color and takes the absolute value of the difference to create the result color. For those not familiar with absolute value, the absolute value of a number is the positive value of that same number (e.g., the absolute value of -5 is 5, and the absolute value of 5 is also 5). If the blend color is white, the base color will be inverted. If the blend color is black, the Difference Blend mode does nothing. Mathematically, the Difference Blend mode is defined as:

In Each Channel, Result Color = |Base Color - Blend Color|

The Difference Bend is great for aligning images. A typical example is when a camera is set up on a tripod and different exposures are taken of the same scene in order to capture the wide dynamic range of the image. Those exposures are then combined in the computer. If the images are shot on film and scanned, they will not likely align perfectly. Instead, they will need to be aligned in the computer. Even images shot with a digital camera can come out misaligned if the camera was slightly moved between exposures (the camera may have been touched in order to change settings).

To align the images using the Difference Blend mode, the blend layer is set to the Difference Blend mode. Where the images are not aligned properly, the image will have an engraved look.

Figure 1: Image that Requires Alignment of Two Layers

Figure 1 shows an image that used the Difference Blend mode to align two copies of the image.

Figures 2 and 3 show the image with the Blend mode set to Difference on the second layer. Figure 2 shows the image with the layers out of alignment. Figure 3 shows the image after the layers have been aligned. Figure 4 shows the Layers Palette with the second layer set to the Difference Blend mode.

Figure 2: Image before Alignment of the Layers (Top Layer set to Difference Blend Mode)
Figure 3: Image after Alignment of the Layers (Top Layer set to Difference Blend Mode)
Figure 4: Layers Palette with Difference Blend Mode on Image 2 Layer

 

Table 1 summarizes the Difference Blend mode.

 

  Table 1: Difference Blend Mode
What it does
In each channel, the Difference Blend mode subtracts the blend color from the base color and takes the absolute value of the difference to create the result color. If the blend color is white, the base color will be inverted. If the blend color is black, the Difference Blend mode does nothing.
Formula
In Each Channel, Result Color = |Base Color - Blend Color|
Uses
Used for aligning images.

 

Exclusion Blend Mode

The Exclusion Blend mode is very similar to the Difference Blend mode except that the contrast is lower with the Exclusion Blend mode. For the Exclusion Blend mode, if the blend color is white, the base color will be inverted. If the blend color is black, the Difference Blend mode does nothing.

Aside from some special effects, the main use for the Difference Bend, for photographers, is for aligning images. The Exclusion Blend mode provides an alternative to the Difference Blend mode for this purpose.

Figures 5 and 6 show two copies of the image from Figure 1 being aligned with the use of the Exclusion Blend mode. In both figures, the Blend mode is set to Exclusion on the second layer. Figure 5 shows the image with the layers out of alignment. Figure 6 shows the image after the layers have been aligned. Figure 7 shows the Layers Palette with the second layer set to the Exclusion Blend mode. Figures 5 and 6 can be compared with Figures 2 and 3 to see the distinction between the Difference Blend mode and the Exclusion Blend mode for aligning images.

Figure 5: Image before Alignment of Layers (Top Layer set to Exclusion Blend Mode)
Figure 6: Image after Alignment of the Layers (Top Layer set to Exclusion Blend Mode)
Figure 7: Layers Palette with Exclusion Blend Mode on Image 2 Layer

 

Table 2 summarizes the Exclusion Blend mode.

 

  Table 2: Exclusion Blend Mode
What it does
The Exclusion Blend mode is very similar to the Difference Blend mode except that the contrast is lower with the Exclusion Blend mode. For the Exclusion Blend mode, if the blend color is white, the base color will be inverted. If the blend color is black, the Difference Blend mode does nothing.
Uses
Used for aligning images.

 

Hue Blend Mode

The Hue Blend mode creates the result color by combining the luminance and saturation of the base color with the hue of the blend color.

The Hue Blend mode can be used to change hues in an image while maintaining the tonal and saturation values of the original image. This is done by adding a layer of the new replacement hue and using a mask to restrict the hue to only the areas that need to be replaced.

This method is shown in Figures 8 and 9. Suppose, for some unknown reason, that it was desired to have a green eyed bird instead of the yellow eyed bird shown in Figure 8. A new, green, Solid Color Fill Layer was added (the new layer was labeled as the Eye Color layer). The Blend mode of the Eye Color layer was set to Hue, and the Opacity was set to get the desired effect. Figure 8 shows the image before the hue step, Figure 9 shows it afterwards. Figure 10 shows the Layers Palette with the Eye Color layer set to the Hue Blend mode.

Figure 8: Image before Adjustment
Figure 9: Image Adjusted with Hue Blend Mode
Figure 10: Layers Palette with the Eye Color Layer on Hue Blend mode

 

Table 3 summarizes the Hue Blend mode.

 

  Table 1: Hue Blend Mode
What it does
The Hue Blend mode creates the result color by combining the luminance and saturation of the base color with the hue of the blend color.
Uses
Used for changing hues in an image while maintaining the tonal and saturation values of the original image.

 

Saturation Blend Mode

The Saturation Blend mode creates the result color by combining the luminance and hue of the base color with the saturation of the blend color. If the blend color is gray, the Saturation Blend mode does nothing.

The Saturation Blend mode can be used to modify the saturation of an image or parts of an image. Another use for the Saturation Blend mode is for special effects involving the manipulation of the saturation of an image.

An example of the Saturation Blend mode's use for special effects is shown in Figures 11 and 12. For this special effect, the image was duplicated (the new layer was labeled as the Saturation layer) A selection was made of the butterfly. The selection was inverted and the selected portion of the layer was filled with neutral gray. This produced a layer where everything was gray except for the butterfly. The Blend mode of the Saturation layer was set to Saturation, and the Opacity was set to get the desired effect. Figure 11 shows the image before the saturation step, Figure 12 shows it afterwards. Figure 13 shows the Layers Palette with the Saturation layer set to the Saturation Blend mode. While this image could have been created a number of different ways, the advantage of using the Saturation Blend mode on a layer is the flexibility with regard how the saturation is managed. For example, the gray on the Saturation layer could have been applied using a radial gradient. Then, the saturation would have been at full strength in the center of the image and faded to black and white as it moved toward the edges.

Figure 11: Image before Adjustment
Figure 12: Image Adjusted with Saturation Blend Mode
Figure 13: Layers Palette with the Saturation Layer on Saturation Blend mode

 

Table 4 summarizes the Saturation Blend mode.

 

  Table 4: Saturation Blend Mode
What it does
The Saturation Blend mode creates the result color by combining the luminance and hue of the base color with the saturation of the blend color. If the blend color is gray, the Saturation Blend mode does nothing.
Uses
Used for editing of saturation or for special effects involving the manipulation of the saturation of an image.

 

Color Blend Mode

The Color Blend mode creates the result color by combining the luminance of the base color with the hue and saturation of the blend color.

The Color Blend mode is good for tinting images. This is done by adding a solid color layer and setting the Blend mode of the layer to Color. The Opacity is then adjusted to produce the degree of tinting required.

This tinting approach was used in Figures 14 and 15. Figure 14 shows a black and white image. A Solid Color Fill layer was added to the black and white image, the Blend mode of the Solid Color Fill layer was set to Color, and the Opacity was adjusted. Figure 15 shows the image after the Solid Color Fill layer was added. Figure 16 shows the Layers Palette with the Solid Color Fill layer set to the Color Blend mode.

Figure 14: Image before Tinting
Figure 15: Image after Tinting with Color Blend Mode
Figure 16:  Layers Palette with Color Blend Mode on Color Fill 1 Layer

 

Table 5 summarizes the Color Blend mode.

 

  Table 5: Color Blend Mode
What it does
The Color Blend mode creates the result color by combining the luminance of the base color with the hue and saturation of the blend color.
Uses
Used for tinting images.

Luminosity Blend Mode

The Luminosity Blend mode creates the result color by combining the hue and saturation of the base color with the luminance of the blend color. In essence, any editing done on a layer set to the Luminosity Blend mode only affects the luminosity (tonality) of the layer -- it does not affect the color of the image.

Figure 17:  Image with Sharpening Color Halos (See Close-Ups)

One of the biggest uses for the Luminosity Blend mode is during sharpening. Sharpening can produce color halos. By sharpening on a separate layer and setting the blend mode of the sharpening layer to Luminosity, only the luminosity of the image will be sharpened. This will eliminate any color halos.

Figure 17 shows an image that had issues with color halos.

Figures 18 and 19 show close-ups of the sharpened image. The sharpening was performed on a separate layer (Sharpen Output layer). In Figure 18, the Sharpen Output layer Blend mode was set to normal. As can be seen along the edge of the vertical pod of the plant, the sharpening produced a color halo. Figure 19 shows the image after the Sharpen Output layer Blend mode was changed to Luminosity. The image clearly shows that the color halo has disappeared. Figure 20 shows the Layers Palette with the Sharpen Output Layer set to the Luminosity Blend mode.

Figure 18: Image before Adjustment
Figure 19: Image Adjusted with Luminosity Blend Mode.
Figure 20: Layers Palette with Luminosity Blend Mode on Sharpen Output Layer

 

Table 6 summarizes the Luminosity Blend mode.

 

  Table 6: Luminosity Blend Mode
What it does
The Luminosity Blend mode creates the result color by combining the hue and saturation of the base color with the luminance of the blend color.
Uses
Used for eliminating color halos caused by sharpening.

 

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