«PROFESSIONAL USER GUIDE © 2007 Adobe Systems Incorporated. All rights reserved. Copyright Adobe® After Effects® CS3 User Guide for Windows® and ...»
8-bpc pixels can have values for each color channel from 0 (black) to 255 (pure color). 16-bpc pixels can have values for each color channel from 0 (black) to 32,768 (pure color). If all three color channels have the maximum, purecolor value, the result is white. 32-bpc pixels can have values under 0.0 and values over 1.0 (pure color); this means that 32-bpc color in After Effects is also high dynamic range (HDR) color. HDR values can be much brighter than white. (See “High dynamic range color” on page 235.) Glow effect and Gaussian Blur effect applied to image in 32-bpc project (left) and 16-bpc project (right) Set the project color depth to 32 bpc to work with HDR footage or to work with over-range values—values above 1.0 (white) that aren’t supported in 8- or 16-bpc mode. Over-range values preserve the intensity of highlights, which is just as useful for synthetic effects such as lights, blurs, and glows as it is for working with HDR footage. The headroom provided by working in 32 bpc prevents many kinds of data loss during operations from color correction to color profile conversion. Even if you’re using 8-bpc footage and are creating movies in 8-bpc formats, you can obtain better results by having the project color depth set to 16 or 32 bpc. Working in a higher bit depth provides higher precision for calculations and greatly reduces quantization artifacts, such as banding in gradients.
Because 16-bpc frames use half the memory of 32-bpc frames, rendering previews in a 16-bpc project is faster, and RAM previews can be longer than in a 32-bpc project. 8-bpc frames use even less memory, but the tradeoff between quality and performance can be quite visible in some images at a project color depth of 8 bpc.
• Alt-click (Windows) or Option-click (Mac OS) the Project Settings button in the Project panel.
• Choose File Project Settings or click the Project Settings button in the Project panel, and choose a color depth from the Depth menu.
AFTER EFFECTS CS3 235 User Guide
Project Settings button in the Project panel
You can specify a color depth for each render item, which overrides the project color depth when rendering for final output. You can also specify the color depth to use for each output item in the output module settings.
Though many effects can work with all color depths, some effects work only with lower color depths. You can set the Effects & Presets panel to only show effects that work with your current project color depth. (See “Effects & Presets panel overview” on page 350.) Note: To change the format in which color values are shown in the Info panel and in some effect controls, choose an option such as Percent or Web from the Info panel menu. Choosing Auto Color Display automatically switches between 8 bpc, 16 bpc, and 32 bpc, depending on the project’s color depth.
See also “Work with render settings” on page 597 “Work with output module settings” on page 599 High dynamic range color The dynamic range (ratio between dark and bright regions) in the physical world far exceeds the range of human vision and of images that are printed on paper or displayed on a monitor. Low dynamic range 8-bpc and 16-bpc color values can represent RGB levels only from black to white; this represents an extremely small segment of the dynamic range in the real world.
High dynamic range (HDR), 32-bpc floating-point color values can represent brightness levels much greater than white, including objects as bright as a candle flame or the Sun.
Because we can see only a subset of the luminance values in a real-world scene in an HDR image on a monitor, it is sometimes necessary to adjust the exposure, or the amount of light captured in an image, when working with an HDR image. Adjusting the exposure of an HDR image is like adjusting the exposure when photographing a scene in the real world, allowing you to bring detail out of very dark areas or very bright areas.
You can use the HDR Compander effect to compress the dynamic range of a layer with an HDR footage item as its source. In this way, you can use tools that don’t support HDR, such as 8-bpc and 16-bit effects. When you’re done, use the HDR Compander to undo the dynamic range compression. The HDR Highlight Compression effect lets you compress the highlight values in an HDR image so that they fall within the value range of a low dynamic range image.
Jonas Hummelstrand’s website provides a collection of resources for understanding and using HDR color in After Effects: www.adobe.com/go/learn_ae_jonas32bpc.
Select a color or edit a gradient In many contexts, you can click an eyedropper button to activate the eyedropper tool, or you can click a color swatch to open a color picker. If you use the Adobe Color Picker, you can also activate the eyedropper from the Adobe Color Picker dialog box.
If you click a gradient swatch for a shape layer’s stroke or fill, or click Edit Gradient in the Timeline panel, the Adobe Color Picker opens as the Gradient Editor, with additional controls for editing gradients included at the top of the dialog box.
Note: The sampleImage expression samples the color values in a way similar to that of the eyedropper. Use this method to use color values of specific pixels as input into an expression. (See “Layer General attributes and methods” on page 570.) C A B
A. Opacity stop B. Color stop C. Opacity midpoint D. Eyedropper E. New-color rectangle F. Original-color rectangle Choose a color picker ❖ Choose Edit Preferences General (Windows) or After Effects Preferences General (Mac OS), and do one
of the following:
• To use the color picker provided by the operating system, select Use System Color Picker.
• To use the Adobe Color Picker, deselect Use System Color Picker.
Select a color with the Adobe Color Picker 1 Click a color swatch to display the Adobe Color Picker.
2 (Optional) To prevent panels from updating with the results of your color selection until you accept the color by clicking OK, deselect Preview in the Color Picker dialog box. The Preview option is not available in all contexts.
Note: Selecting Preview is convenient for seeing the results of your color selections before you commit them, but it can also decrease performance, as new images are rendered for the preview in the Composition panel or Layer panel.
3 Select the component you want to use to display the color spectrum:
H Displays all hues in the color slider. Selecting a hue in the color slider displays the saturation and brightness range of the selected hue in the color spectrum, with the saturation increasing from left to right and brightness increasing from bottom to top.
S Displays all hues in the color spectrum with their maximum brightness at the top of the color spectrum, decreasing to their minimum at the bottom. The color slider displays the color that’s selected in the color spectrum with its maximum saturation at the top of the slider and its minimum saturation at the bottom.
B (in the HSB section) Displays all hues in the color spectrum with their maximum saturation at the top of the color spectrum, decreasing to their minimum saturation at the bottom. The color slider displays the color that’s selected in the color spectrum with its maximum brightness at the top of the slider and its minimum brightness at the bottom.
R Displays the red color component in the color slider with its maximum brightness at the top of the slider and its minimum brightness at the bottom. When the color slider is set to minimum brightness, the color spectrum displays colors created by the green and blue color components. Using the color slider to increase the red brightness mixes more red into the colors displayed in the color spectrum.
G Displays the green color component in the color slider with its maximum brightness at the top of the slider and its minimum brightness at the bottom. When the color slider is set to minimum brightness, the color spectrum displays colors created by the red and blue color components. Using the color slider to increase the green brightness mixes more green into the colors displayed in the color spectrum.
B (in the RGB section) Displays the blue color component in the color slider with its maximum brightness at the top of the slider and its minimum brightness at the bottom. When the color slider is set to minimum brightness, the color spectrum displays colors created by the green and red color components. Using the color slider to increase the blue brightness mixes more blue into the colors displayed in the color spectrum.
4 Do any of the following:
• Drag the triangles along the color slider, or click inside the color slider to adjust the colors displayed in the color spectrum.
• Click or drag inside the large square color spectrum to select a color. A circular marker indicates the color's position in the color spectrum.
Note: As you adjust the color using the color slider and color spectrum, the numeric values change to indicate the new color. The top rectangle to the right of the color slider displays the new color; the bottom rectangle displays the original color. Click the bottom rectangle to reset the color to the original color.
• For HSB, specify hue (H) as an angle, from 0˚ to 360˚, that corresponds to a location on the color wheel. Specify saturation (S) and brightness (B) as percentages (0 to 100).
• For RGB, specify component values. You can set colors to under-range and over-range values (outside of the range of 0.0 to 1.0) in an HDR project.
• For #, enter a color value in hexadecimal form. This color format is common in web workflows.
AFTER EFFECTS CS3 238 User Guide Edit a gradient A gradient is defined by color stops and opacity stops. Each stop has a location along the gradient and a value for color or opacity. The values between stops are interpolated. By default, the interpolation is linear, but you can drag the opacity midpoint or color midpoint between two stops to alter the interpolation.
• To add a color stop or opacity stop, click below or above the gradient bar in the Gradient Editor dialog box.
• To remove a stop, drag it away from the gradient bar, or select the stop and click Delete.
• To edit a stop’s value, select it and adjust the Opacity value or use the Adobe Color Picker controls beneath the gradient editor controls.
• To choose a gradient type, click the Linear Gradient or Radial Gradient button in the upper-left corner of the Gradient Editor dialog box.
Note: Use the Style property to choose a gradient type for the Gradient Overlay layer style.
About color correction and adjustment When you assemble a composition, you often need to adjust the colors of one or more of the layers to correct their
colors. Such adjustments can be for any of a number of reasons. Some examples:
• You need to make it seem as if multiple footage items were shot under the same conditions so that they can be composited or edited together.
• You need to adjust the colors of a shot so that it seems to have been shot at dusk instead of noon.
• You need to adjust the exposure of an image to recover detail from the over-exposed highlights.
• You need to enhance one color in a shot because you will be compositing a graphic element over it with that color.
• You need to restrict colors to a particular range, such as the broadcast-safe range.
After Effects includes many built-in effects for color correction. See “Color Correction effects” on page 387.
The Color Finesse plug-in included with After Effects includes excellent color-correction tools. For more information, see the Color Finesse documentation in the following folder: Adobe After Effects CS3/Additional Documentation/Color Finesse 2.
The Camera Raw plug-in can be used to correct and adjust still images in JPEG, TIFF, and various camera raw formats.
John Dickinson provides visual aids on his website that illustrate how to use the Curves and Levels effects for color adjustments: www.adobe.com/go/learn_ae_jdcurves and www.adobe.com/go/learn_ae_jdlevels.
See also “Introduction to Camera Raw” on page 86 “Broadcast-safe colors” on page 250
A color space is a variant of a color model. A color space is distinguished by a gamut (range of colors), a set of primary colors (primaries), a white point, and a tone response. For example, within the RGB color model are a number of color spaces, including—in decreasing order of gamut size—ProPhoto RGB, Adobe RGB, sRGB IEC61966-2.1, and Apple RGB. Although each of these color spaces defines color using the same three axes (R, G, and B), their gamuts and tone response curves are different.
Harry Frank provides a video tutorial that shows how and why to use color conversion expressions to convert colors
from RGB to HSL when randomly varying colors; the specific example that he shows uses the Radio Waves effect:
Though many devices use red, green, and blue components to record or express color, the components have different characteristics—for example, one camera’s blue is not exactly the same as another camera’s blue. Each device that records or expresses color has its own color space. When an image moves from one device to another, image colors may look different because each device interprets the RGB values in its own color space.
Color management uses color profiles to convert colors from one color space to another, so colors look the same from one device to another.
For information on color spaces and color management in After Effects, go to the Adobe website at www.adobe.com/go/learn_ae_colormanagementpaper.
See also“Color management” on page 241
About gamma and tone response A color space’s tone response is the relationship of light intensity to the signal that creates or records (perceives) the light.