Creating Effects in the Color FX Room

This section outlines some of the most common operations you’ll perform in the Color FX room. For more information, see:

Using Single Input Nodes

The simplest use of this room is to apply one or two single-input nodes to create a stylized effect. In this case, all you need to do is add the nodes you want to use, connect them together in the order in which you want them applied, and then add an Output node to the very end.

In the following example, a Bleach Bypass node (which alters the saturation and contrast of an image to simulate a chemical film process) is followed by a Curve node (to further alter image contrast), which is followed by the Output node that must be added to the end of all node trees.

Figure. Applying two nodes to an output node for a simple effect.

Using Layering Nodes

A more sophisticated use of nodes is to use multi-input nodes to combine two or more separately processed versions of the image for a combined effect.

In one of the simplest examples, you can tint an image by attaching a Color node (which generates a user-definable color) to one input of a Multiply layering node.

Figure. Attaching a Color node to a Multiply node for a tint.

This adjustment multiplies the color with the corrected image. (Remember, disconnected inputs always link to the corrected image data.) Because of the way image multiplication works, the lightest areas of the image are tinted, while progressively darker areas are less tinted, and the black areas stay black.

Figure. Before-and-after tint effect in Color FX room.

In a slightly more complicated example, the image is processed using three nodes: a Duotone node (which desaturates the image and remaps black and white to two customizable colors), a Curve node (to darken the midtones), and a Blur node. The result is connected to one input of an Add node (with both Bias parameters set to 1).

Figure. Four nodes creating a diffuse glow.

The Duotone, Curve, and Blur nodes tint, darken, and blur the image prior to adding it to the corrected image (coming in via input 2), and the result is a diffusion effect with hot, glowing highlights.

Figure. Before-and-after diffuse glow effect in Color FX room.

Math Layering Nodes Explained

The layering nodes shown in Using Layering Nodes use simple math to combine two differently modified versions of the image together. These mathematical operations rely on the following numerical method of representing tonality in each of the three color channels of an image:

  • Black = 0 (so black for RGB = 0, 0, 0)

  • Midtone values in each channel are fractional, from .00001 through .999999

  • White = 1 (so white for RGB = 1, 1, 1)

Bear these values in mind when you read the following sections.

Add

The pixels from each input image are added together. Black pixels have a value of 0, so black added to any other color results in no change to the image. All other values are raised by the sum of both values. The order in which the inputs are connected doesn’t matter.

Add operations are particularly well suited to creating aggressive glowing effects, because they tend to raise levels very quickly depending on the input images. Bear in mind that the best way of controlling which areas of the image are being affected when using an Add operation is to aggressively control the contrast of one of the input images. The darker an area is, the less effect it will have.

Note: By default, the Bias parameters of the Add node divide each input image’s values by half before adding them together. If the results are not as vivid as you were hoping for, change the Source 1 and Source 2 Bias parameters to 1.

Difference

The pixels from the image that’s connected to Source 1 are subtracted from the pixels from the image that’s connected to Source 2. Black pixels have a value of 0, so any color minus black results in no change to the Source 1 image. The order in which the inputs are connected matters.

This node is useful for darkening the Source 1 image based on the brightness of the Source 2 image.

Multiply

The pixels from each input image are multiplied together. White pixels have a value of 1, so white multiplied with any other color results in no change to the other image. However, when black (0) is multiplied with any other color, the result is black.

When multiplying two images, the darkest parts of the images remain unaffected, while the lightest parts of the image are the most affected. This is useful for tinting operations, as seen previously, as well as for operations where you want to combine the darkest portions of two images.

Creating Layered Effects Using Mattes

An extremely important method of creating layered effects involves using a grayscale matte to control where in an image two inputs are added together. The Alpha Blend node has three inputs that work together to create exactly this effect.

Figure. The Alpha Blend node.

This node blends the Source 2 input to the Source 1 input in all the areas where the Source 3 Alpha input image is white. Where the Alpha input image is black, only the Source 1 input is shown.

Any grayscale image can be used to create a matte that you can connect to the Alpha input, for a variety of effects. In the following example, a Curve node is used to manipulate the contrast of an image so that an Edge Detector node can better isolate the edges to create a grayscale matte; a Blur node is used to soften the result, and an Invert node is used to reverse the black and white areas of the matte so that the edges of the face become the areas of the matte that are transparent, or not to be adjusted.

Figure. Creating a matte using the Curve, Edge Detector, Blur, and Invert nodes.

This matte is connected to the Alpha input of the Alpha Blend node (the third input). A Blur node is then connected to the Source 2 input.

Figure. Using a generated matte to isolate a blur effect using an Alpha Blend node.

The Blur node blurs the corrected image, but the matte image that’s connected to the Alpha input limits its effect to the areas of the image that don’t include the image detail around the edges that were isolated using the Edge Detector node.

Figure. Before and after isolated blur effect in Color FX room.

As you can see, the image that’s connected to the Alpha input of the Alpha Blend node limits the way the Source 1 and Source 2 inputs are combined. This is but one example of the power of the Alpha Blend node. You can use this node to limit many different effects.