File formats, About file formats and compression – Adobe Photoshop CS4 User Manual
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USING PHOTOSHOP CS4
Saving and exporting images
Last updated 1/10/2010
2
In the Export Layers To Files dialog box, under Destination, click Browse to select a destination for the exported
files. By default, the generated files are saved in the sample folder as the source file.
3
Enter a name in the File Name Prefix text box to specify a common name for the files.
4
Select the Visible Layers Only option if you want to export only those layers that have visibility enabled in the Layers
panel. Use this option if you don’t want all the layers exported. Turn off visibility for layers that you don’t want
exported.
5
Choose a file format from the File Type menu. Set options as necessary.
6
Select the Include ICC Profile option if you want the working space profile embedded in the exported file. This is
important for color-managed workflows.
7
Click Run.
File formats
About file formats and compression
Graphics file formats differ in the way they represent image data (as pixels or vectors), in compression techniques, and
which Photoshop features they support. With a few exceptions (for instance Large Document Format (PSB),
Photoshop Raw, and TIFF), most file formats cannot support documents larger than 2 GB.
Note: If a supported file format does not appear in the appropriate dialog box or submenu, you may need to install the
format’s plug-in module.
About file compression
Many file formats use compression to reduce the file size of bitmap images. Lossless techniques compress the file
without removing image detail or color information; lossy techniques remove detail. The following are commonly used
compression techniques:
RLE (Run Length Encoding)
Lossless compression; supported by some common Windows file
formats.
LZW (Lemple-Zif-Welch)
Lossless compression; supported by TIFF, PDF, GIF, and PostScript language file formats.
Most useful for images with large areas of single color.
JPEG (Joint Photographic Experts Group)
Lossy compression; supported by JPEG, TIFF, PDF, and PostScript
language file formats. Recommended for continuous-tone images, such as photographs. JPEG uses lossy compression.
To specify image quality, choose an option from the Quality menu, drag the Quality pop-up slider, or enter a value
between 0 and 12 in the Quality text box. For the best printed results, choose maximum-quality compression. JPEG
files can be printed only on Level 2 (or later) PostScript printers and may not separate into individual plates.
CCITT
A family of lossless compression techniques for black-and-white images, supported by the PDF and PostScript
language file formats. (CCITT is an abbreviation for the French spelling of International Telegraph and Telekeyed
Consultive Committee.)
ZIP
Lossless compression; supported by PDF and TIFF file formats. Like LZW, ZIP compression is most effective for
images that contain large areas of single color.
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