Walker Effects Manual

Color Space

This plug-in provides access to a wide variety of standard color models. Because Color Space works within the paradigm of After Effects (an RGBA system) Color Space is somewhat limited to being a true color model converter. What it does offer is a reasonable approach to using other color spaces within After Effects.

Using Color Space is generally a multi-step process. First Color Space is used to convert a layer to a Color Model other than RGB. This exposes the channels of the selected color space temporarily storing the values in the RGB and alpha channels which you can then manipulate with any effect. Color Space is then applied again to reverse the Color Model back to RGB.

There are many benefits to using color spaces to manipulate images. For example, HLS can be used to modify the hue channel independently of the lightness and saturation. Or you can even create color corrections based on CMYK. The full range of color models is described below.

Color Model

Color Space has the ability to convert to and from most major color models. When a Color Model is selected, the components of the new color space are respectively stored in the RGBA channels of the layer. This is indicated in the name of the View control. For example, choosing HLS will effectively store the Hue in the Red channel, the Lightness in the Green, and the Saturation in the Blue, while the View control will read 'View [H|L|S|A]'.

Almost all Color Models, need only three channels and the fourth channel (the alpha) is simply passed through the effect remaining unchanged. The only exception is CMYK which requires 4 channels.

Brief definitions for each Color Model are given below. For a better understanding of color spaces, please refer to these sources:
Poynton's Color FAQ
David Bourgin's Color FAQ

RGB

This is the standard color space that After Effects operates in. Since the layer is already in RGB color space, choosing this Color Model has no effect on the input channels. This mode is provided as a useful way to view and isolate the RGB channels.

HLS

This color model represents color as Hue, Lightness and Saturation. This is a standard color space most often found in color pickers as an alternative to RGB.

HSV

Similar to HLS, HSV represents colors as Hue, Saturation and Value. Unlike Lightness, Value represents the intensity of color. A Value of 100% means that the color is fully saturated and bright, but is not white as Lightness at 100% would be.

CMY

The CMY space offers the inverse space of RGB. These color channels represent the subtractive components of color: Cyan, Magenta and Yellow.

CMYK

Based on the CMY color space, CMYK further extracts the Black channel (K) from the image. This is used in printing where it is more favorable to use black ink rather than mixing colors. This Color Model stores the K channel in the alpha, and will lose any preexisting alpha. If you need to preserve the alpha, you can premultiply the layer and reintroduce the transparency after Color Space is used.

XYZ

The XYZ Color Model is a CIE system based on human vision. The Y component defines luminance while X and Z are respectively the red-yellow and blue-yellow representations. This Color Model is most often used as a transitional model to other color spaces.

xyY

Derived from XYZ, xyY represents colors as coordinates within the Chromaticity Diagram. The channels x and y are the coordinates, while Y is the luminance. Note that Channels In Color is not available with for this Color Model.

Y'UV

This is the analog standard color space used in the PAL video format. Y is luminance while U and V are the color components.

Y'IQ

This is the analog standard color space used in the NTSC video format. Y is luminance while I and Q are the color components.

Lab

This is another CIE color system based on the XYZ color space. Luminance is measured by L while a and b represent the red-blue and yellow-blue components.

Luv

The Luv Color Model is also a CIE color system based on XYZ. L defines Luminance, while u and v define chrominance.

Reverse

This checkbox determines whether Color Space is converting from or to the chosen Color Model. When not checked, Color Space converts to the specified Color Model, storing the new channels in the RGBA channels of the layer. Generally Color Space is applied twice: the first effect converts to the Color Model, and the second effect has Reverse enabled to convert the Color Model back to RGB. When Reverse is enabled, you must specify which Color Model to convert from, and the output of the effect will always be in the RGBA space.

Premultiply With Alpha

View [1,2,3,4]

As a means to work with the components of each Color Model, the View mode provides the ability to see each channel individually. The name of the View control will change to reflect the current arrangement of channels. For example, when using the HLS color model, the View menu name will change to 'View [H|L|S|A]'. This indicates that the Hue is stored in the Red channel, the Lightness in Green, the Saturation in Blue and the Alpha in the Alpha channel.

Composite

The default View mode, Composite, outputs all channels of the Color Space. When converting to and from a color space, this mode must be set.

1, 2, 3, 4

Each of the numbered View modes relate to the ordered channels of the Color Model. With each model, the View name updates to reflect the ordering. For example, with the Color Model CMYK chosen, the View mode name will be 'View [C|M|Y|K]'. Furthermore, the selected channel will be named next to the Isolate Channel checkbox. For example, if you choose View mode 2 with the Lab Color Model, the name will be shown 'a -> Green', meaning that component 'a' of Lab is being stored in the Green channel of the layer.

Isolate Channel

This checkbox is only enabled when the View mode is set to a specific channel (1,2,3 or 4). When enabled, Isolate Channel will cause the current channel to be placed in its respective Red, Green, or Blue channel. The reason to use this feature is if you are using Color Space to separate the channels into individual layers and want recombine them later using Color Space.

Channels In Color

When this checkbox is on, the selected channel will be rendered in color, rather than in grayscale. For some channels, color is not an option and this checkbox may be disabled. The purpose for viewing channels in color is to help understand what the channel represents, and can even be used to generate interesting color treatments.

Blend With Original

Use this slider to blend the result of the effect with the original input layer. If Blend With Original is set to 100%, the effect will not render.