The Digital Eye: Blending Layers

Sometimes your image just doesn’t have that eye-popping zing that propels it off the printed page. Adjusting color with Levels, Curves or Hue /Saturation may spice up the image but still, the color relationships don’t quite cut the mustard. Enter Blend Modes!

 

Imagine that you place two color transparencies on a light table. In your mind’s eye you can see their content as the light passes through them. Now, imagine that one of the transparencies is placed on top of the other. The colors of both slides mix together and become darker and a bit more saturated.

 

Color Magic

Now, imagine that you have a box of special magic gels. Each gel can be independently sandwiched between the two slides to control the color relationship of the superimposed colors. In the parlance of digital art software, these gels are called Blend Modes, and you’ll find them in several of the features of image editing and vector graphic software.

Blend modes mix the colors of aligned pixels on consecutive layers. They can also be assigned to the painting and editing tools, to fills, strokes and layer styles.

 

A Matter of Principle

The principle behind blend modes is quite simple. An algorithm affects the aligned pixels on two consecutive layers. Applied to the top layer, the algorithm mixes the color of the two layers in unique ways. Opposite colors like reds and greens may cancel each other and produce areas of dark gray or black. Colors that are closer to each other on the color wheel, like reds and yellows, may produce richer, more saturated oranges. With 29 blend modes to choose from in Photoshop, 16 in Illustrator, and 21 in Corel PaintShop Pro you can imagine the many possibilities—no matter what software you’re using.

 

Do the Math

A blend mode is a mathematical formula. When a blend mode is assigned to a layer the numerical values of each pixel is calculated and applied, depending on the mode, to the aligned pixels on the layer immediately below. Similarly, when a blend mode is assigned to a brush, the foreground color affects the pixels that the brush touches with the formula. The color mode of an image also affects the results. The same blend mode applied to an RGB, CMYK, or Lab layer may produce different results (see Figure 1 A/B).

 

Opacity or Transparency

The level of opacity is the primary factor that controls the strength of the blended effect. With one hundred percentage points of opacity to choose from—from invisible to completely opaque—the strength of the blended layer can be controlled to achieve precise results (see Figure 2). Furthermore, a layer mask can be added to control the precise location and strength of the blend.

 

Universal Blending

All types of layers are affected by blend modes including content layers, adjustment layers, fill layers, shape layers and smart objects. The modes are divided into five categories on the Layers panel in Photoshop (see Figure 3). The categories include: Combination, Darken, Lighten, Contrast, Comparative, Component, and Additional. Rather than consume the limited space of this article with descriptions of each blend mode, I’ll include two websites. One for Adobe and one for Corel. Each provides accurate descriptions of each blend mode.

Of course, you’ll learn a lot more by experimenting with blend modes. The techniques that follow demonstrate some of the practical applications and how you can use them to create great looking effects that enhance the visual impact of your image.

 

Identical Content

Blending layers with similar content can produce much richer colors and superior contrast, and applying more than one blend mode to a series of consecutive layers can knock the image out of the park. If the picture lacks contrast and the colors are not up to snuff, this technique will augment the colors and add richness and depth to a not-so-great image (see Figure 4).

An image captured directly from a scanner or digital camera contains a single layer called Background. A background does not support opacity or blend modes. It’s best to convert it to a layer (Layer > New > Layer from Background…) and then duplicate it (Layer > Duplicate Layer…) to make an identical copy. It’s always a good idea to name the layer after the blend mode you are to apply—in this case we'll use the blend mode Linear Light.

Click the new layer and choose Linear Light from the Mode menu. Linear Light produces a hyper-saturated look, but it can blow out lighter areas if applied with too much intensity, (see Figure 5).

Duplicate the layer again. Name the new layer Hard Light, and assign the Hard Light blending mode. The image contrast is further enhanced and the colors become more saturated but areas are still blown out. Let’s push back a little. Drag the Opacity slider of each layer to better balance the color and contrast until you’re satisfied with the results. Finally, add layer mask to control the location of the effect on the blended layer, (see Figure 6).

Experiment with different blend modes while creating additional layers and applying blend modes at varying degrees of opacity to vary the effect.

 

Adjustments and Gradients

A lackluster image, like the flowers and cacti in Figure 7 can be enhanced by adding a blended adjustment layer. For even more punch, a gradient fill layer can be added to modulate the colors.

 

  1. In the Layers panel, click on the Background layer of the original image.
  2. Click on the Vibrance icon in the Adjustments panel and adjust the vibrancy to a little more than you need. Leave the Saturation slider at the default (see Figure 8)
  3. Assign a Hard Light blend mode to the Vibrance adjustment layer.
  4. Drag the opacity slider to diminish the effect until the desired result is achieved.
  5. Click the Fill/Adjustments icon at the bottom of the Layers panel and choose Gradient. Choose a gradient from the dialog box or click on the gradient ramp and display the gradient editor to make a custom gradient (see Figure 9).
  6. Assign a Soft Light blend mode to the layer (see Figure 10) and adjust the opacity to control the strength of the effect.
  7. You can alter or even replace the gradient by clicking on the gradient layer thumbnail in the layers panel to once again display the Gradient Layer dialog box.

Once again, experimentation with all of the variables; adjustments, gradients, blend modes and opacities, will lead you to the best results.

 

Blend If

For precision blending that actually controls the core color relationship of two consecutive layers, you may want to try your hand at the Blend If feature. These controls are in the Layer Styles dialog box (see Figure 11), and are accessed by double-clicking the layer’s thumbnail. The Blending Options interface is complex and takes a bit of experimentation to understand just how it can affect the image. Here, we’ll concentrate on the Blend If feature.

The Blend If options picks and chooses which colors on a specific layer will be visible or concealed based on the brightness level of the color information. These controls can be tricky, though with a little practice you’ll get the hang of it. Here is how they work:

The menu displays the options for the color cannel information.

  • Gray specifies a blending range for all channels.
  • Red, Green, or Blue in an RGB image, for example, specifies the blending for the brightness range of a specific color channel.
  • This Layer or Underlying Layer exclusion sliders when dragged, omit pixels of a specific brightness range from selected color channel. The black slider dragged right will omit darker pixels and the white slider dragged left omits lighter pixels. Both expose the content of the underlying layer.

 

Blending Two Layers

Here is an example of the Blend If feature blending the content of two layers.

  1. Open two images. These examples were shot in sequence using a tripod and bracketed to produce two different exposures (see Figure 12). In the top image the cliffs are fine but the sky is blown out. The bottom image has a lovely dramatic sky but the cliffs are too dark. I want to combine them both so that I get perfect cliffs and perfect sky.
  2. Combine the two images into a single image with two layers named Cliffs (on the bottom) and Sky above (see Figure 13).
  3. First look closely at the channel information in the channels panel to find the one with the most contrast. In this case it’s the Red channel (see Figure 14).
  4. Double-click the Sky layer to display the Layer Styles dialog box. In the Blend If menu choose the Red.
  5. Drag the black slider to the right. The areas of the cliffs are replaced by the content from the cliffs layer.
  6. It looks okay, but a bit grainy. The affect needs softening. Press Alt (Win), or Opt (Mac) and drag the right half of the Black slider to the right until the pixel transitions become smooth (see Figure 15).
  7. The final result of blending the two images can be seen in Figure 16.

Sandwiching layers and applying the “magic gels” to layer content pushes the envelope as far as color control goes. In combination with opacity, adjustment layers and layer masks, blend modes perform miraculous color transformations. Both blend modes and Blend If are features that I think you will find quite useful, but as usual, experimentation is the key to finding the best results to produce some seriously cool results.