Apple Motion 4 User Manual
Page 216
An RGB image can comprise image pixels with 256 shades of each of the primary
colors—red, green, and blue. In this case, there are 2
8
(256) shades of each color
component. This creates more than 16.7 million possible colors (256 x 256 x 256 > 16.7
million). The bit depth of an RGB image can be 24 (8 bits for each color), and the bit depth
of an RGBA image (red, green, blue, and an alpha channel) can be 32 (8 bits for each color
+ alpha channel). The bit depth of an alpha channel describes the transparency of each
pixel. Although these images are 24- and 32-bit, such color images are often referred to
as 8-bit (because of the 8 bits per channel).
Note: An RGB image does not necessarily imply 8 bits per pixel.
Motion’s bit depth setting is bits-per-channel. In an 8-bit Motion project, the 256 levels
of color are represented on an integer scale of 0–255 (where 0 represents black and 255
represents white). All of your operations are clamped within that 0–255 range. There is
a one-to-one ratio between each number and its represented color. In 8-bit mode, 16.7
million colors can be represented—equaling the number of possible combinations of
256 different color values from each red, green, and blue channel. Although that is a large
number of colors, it is often helpful to have finer gradations of colors available. Using
floating point calculations, color shades can be subdivided into an enormous amount of
intermediate colors, providing orders of magnitude more colors available to your project
palette. Incredibly small increments of color can be represented in 16-bit float, and even
finer increments in 32-bit float.
The bit depth of your source footage will often determine the bit depth of your project.
Even if your source footage is 8-bit, you may want to work in a project with a higher bit
depth to achieve better results. When you increase the bit depth of your project, you are
not introducing any new color information to the original images. However, operations
such as keying, color correction, applying blur or other filters with high parameter values,
or creating graphics that require very smooth color gradients can benefit from the new
number of possible color levels.
Important:
There is a price for working in higher bit depths, however. And that price is
paid in processing time. Remember also that because Motion is hardware-dependent,
most systems have a limitation on the size of imported files. For more information on the
required hardware, visit the Motion website at
When exporting a 16-bit or 32-bit float project, keep in mind that most file formats
available for export do not support float—including QuickTime (8-bit only). OpenEXR is
a float format. TIFF, PNG, and Adobe Photoshop files support the 16-bit integer format.
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Chapter 6
Creating and Managing Projects