Table 2.1 lists the file formats that can be used, saved, exported, or imported by Photoshop.
Table 2.1. Photoshop File Formats
Photoshop document format
BMP (RLE DIB)
Bitmap format (Windows)
CompuServe Graphical Interchange Format; a web image format supporting transparency; 256 max colors
Photoshop EPS Encapsulated PostScript format
DCS 1.0 2.0
Desktop Color Separations format; a version of EPS; supports CMYK; DCS 2.0 supports spot channels
Joint Photographic Experts Group; most common graphic format for the web and even for print despite its lossy compression; supports RGB, CMYK
Large Photoshop document format (Photoshop Big); allows files over 2GB
Older PC image format; opens in Microsoft Paint
Photoshop Portable Document Format
Photoshop raw format; different than camera raw format; cross-platform binary format supports RGB and CMYK, alpha, and more; cannot contain layers
Mac OS graphic format for the screen; supports RGB, index, grayscale, or bitmap modes
Pixar format; designed for high-end graphics commonly used in 3D work; suports RGB grayscale and single alpha channel
Portable Networking Graphics format; a quality, patent-free alternative to GIF; well-supported web format; supports RGB, grayscale, bitmap modes, transparency; lossless compression options
PBM, PGM, PPM, PNM, PFM
Portable Bitmap formats; family of bitmap screen graphic formats
Scitex Continuous Tone high-end color format; sometimes used for magazine ads
Designed for systems using TrueVision boards; commonly used for video-editing systems
Tagged Image File Format; raster format; supports CMYK, RGB, Lab, indexed color, grayscale, some transparency and Photoshop layers; bit depths of 8, 16, and 32
Paths drawn in Photoshop can be exported as empty paths (no stroke or fill information) for use in Illustrator
Images for mobile devices; 1-bit images contain only black or white pixels
Kodak Cineon Film System format; RGB 16-bit; channel image support
HDR, RGBE, XYZE
High Dynamic Range image formats; support higher range of luminance levels; used in high-end photography for more realistic lighting and exposure
Shockwave Flash format; still images and animations can be exported from ImageReady
Photoshop CS2 ships with optional plug-ins for a variety of file formats that are not needed by the vast majority of Photoshop users (see Figure 2.1). Should you need to work with one or more of these formats, drag the plug-in into the File Formats subfolder of Photoshop's Plug-ins folder. The next time you start Photoshop, the file format will be available.
Figure 2.1. Look for these plug-ins in the Optional Plug-ins folder, inside the Goodies folder, on the Photoshop CD.
Photoshop Format (.psd)
Photoshop's native file format supports all the program's capabilities. Files in this format can be placed in the latest versions of InDesign and GoLive as smart objects and can be opened in Adobe Illustrator. This is the default file format. Most workflows (but not all) benefit from maintaining a file in Photoshop format until it's time to create a final TIFF, EPS, JPEG, or other file. It's also usually a good idea to maintain the original image, with editable type and layers, for future use.
When saving in Photoshop format, you can see that the Save As dialog indicates which features are used in the image (see Figure 2.2). If a check box is grayed out, that feature is unavailable. If you disable a check box, the file is saved as a copy. If you disable a feature (layers, for example) and save the image as a copy, when the image is reopened, that feature is goneno more layers.
Figure 2.2. The Save As dialog in Windows. Options such as Spot Colors, Annotations, Layers, and Alpha Channels are available only if they are actually used in your document.