Adobe AFTER EFFECTS 7.0 - 32-Bpc Projects and Effects; To Expand the Range of Luma Levels

ADOBE AFTER EFFECTS 7.0
User Guide
63
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. You can adjust the exposure of HDR footage by modifying the Exposure control. The Exposure control
doesn’taffecthowfootagewillrender,onlyhowitappearsinpreviews;see“ToadjustexposureofHDRfootage(Pro
only)” on page 145. Use the Exposure effect to make tone adjustments to HDR footage. For more information about
the Exposure effect, see “Exposure effect” on page 414.
32-bpc projects and effects
Create 32-bpc projects in After Effects to work with HDR footage, or to work with over-range values—values above
one (white) that aren’t supported in 8- or 16-bpc mode. Over-range values preserve the details in shadows and the
intensity of highlights.
Because HDR extends dynamic range into shadows as well as highlights, you can bring detail out of dark areas as
well as light areas. Blending operations give more photographic results if linear blending is enabled (see “To enable
linear blending” on page 66). You can create lights in 3D space or apply one of the 32-bpc blur effects, such as Fast
Blur, Gaussian Blur, Channel Blur, Directional Blur, and Box Blur, to HDR footage. You can also apply blending
modes to create interesting interactions between layers.
You can use the HDR Compander effect to compress the dynamic range of HDR footage. 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. For more information about
these effects, see “HDR Compander effect” on page 553 and “HDR Highlight Compression effect” on page 554.
Use the Color Profile Converter effect to convert to or from linear light. For more information about this effect, see
“Color Profile Converter effect” on page 551.
See also
“About color depth” on page 61
“Color depth and effects” on page 351
To expand the range of luma levels
Some file format modules convert 8-bpc luma from certain hardware, such as cameras, to RGB levels within the
range of 16 to 235. In 8-bpc mode, After Effects works with RGB levels from 0 to 255. If blacks or whites appear either
crushed or faded, there may be a luma range mismatch that you can correct by expanding the range of luma levels.
Youcanexpandtherangeofthelumalevelsto0to255withouthavingtoapplyaLevelseffect.Lumaexpansionalso
works with 16-bpc footage and projects.
❖ Select the footage in the Project panel and choose File > Interpret Footage > Main, and select Expand ITU-R 601
Luma Levels.
Note: In 32-bpc projects, After Effects can generate over-range values that let you work with whiter-than-white, or over-
bright, values (for example, values above 235 in an 8-bpc file).