Adobe 13102498 - Photoshop CS3 - Mac User Manual page 468

PHOTOSHOP CS3 461
User Guide
Note: EPS TIFF format and EPS PICT format are more relevant to earlier versions of Photoshop. The current version of
Photoshop includes rasterization features for opening files that include vector data.
Photoshop Raw format
The Photoshop Raw format is a flexible file format for transferring images between applications and computer
platforms. This format supports CMYK, RGB, and grayscale images with alpha channels, and multichannel and Lab
images without alpha channels. Documents saved in the Photoshop Raw format can be of any pixel or file size, but
they cannot contain layers.
The Photoshop Raw format consists of a stream of bytes describing the color information in the image. Each pixel is
described in binary format, with 0 representing black and 255 white (for images with 16-bit channels, the white value
is 65535). Photoshop designates the number of channels needed to describe the image, plus any additional channels
in the image. You can specify the file extension (Windows), file type (Mac OS), file creator (Mac OS), and header
information.
In Mac OS, the file type is generally a four-character ID that identifies the file—for example, TEXT identifies the file
as an ASCII text file. The file creator is also generally a four-character ID. Most Mac OS applications have a unique
file creator ID that is registered with the Apple Computer Developer Services group.
The Header parameter specifies how many bytes of information appear in the file before actual image information
begins. This value determines the number of zeroes inserted at the beginning of the file as placeholders. By default,
there is no header (header size = 0). You can enter a header when you open the file in Raw format. You can also save
the file without a header and then use a file-editing program, such as HEdit (Windows) or Norton Utilities®
(Mac OS), to replace the zeroes with header information.
You can save the image in an interleaved or noninterleaved format. If you choose interleaved, the color values (red,
green, and blue, for example) are stored sequentially. Your choice depends on requirements of the application that
will open the file.
Note: A Photoshop Raw image is not in the same file format as a camera raw image file from a digital camera. A camera
raw image file is in a camera-specific proprietary format that is essentially a "digital negative, " with no filtering, white
balance adjustments, or other in-camera processing.
See also
"Save large documents" on page 442
Digital Negative format (DNG)
Digital Negative (DNG) is a file format that contains the raw image data from a digital camera and metadata that
defines what the data means. DNG, Adobe's publicly available, archival format for camera raw files, is designed to
provide compatibility and decrease the current proliferation of camera raw file formats. The Camera Raw plug-in
can save camera raw image data in the DNG format. For more information about the Digital Negative (DNG) file
format, visit www.adobe.com and search on the term "Digital Negative. " You'll find comprehensive information and
a link to a user forum.
See also
"Save a camera raw image in another format" on page 92