FILE TYPES AND FORMATS : PHOTOSHOP

For general use, these are the most flexible file types (preserving layers, and going back and forth between a wide range of applications):

Photoshop format (PSD) is the default file format for newly created images--and the only format supporting all available image modes (Bitmap, Grayscale, Duotone, Indexed Color, RGB, CMYK, Lab, and Multichannel), guides, alpha channels, spot channels, and layers (including adjustment layers, type layers, and layer effects).

Later versions of Photoshop provide features that are not supported in previous versions. If you edit or save an image using an earlier version of Photoshop, unsupported features are discarded.

Keep in mind the following features when working with earlier versions of Photoshop:

Layer sets, layer color coding, layer clipping paths, fill layers, and layer styles are new in Photoshop 6.0. Layer effects were introduced in Photoshop 5.0; however, these effects do not cover the full range of layer effects provided by Photoshop 6.0. Adjustment layers were introduced in Photoshop 4.0. Paragraph type and advanced type formatting are new in Photoshop 6.0. If you open a Photoshop 6.0 file containing type in Photoshop 5.0 or Photoshop 5.5, the type is displayed in raster form. This means that you can change attributes of the type layer, but you can't edit the text. Color samplers, spot channels, and embedded ICC profiles were introduced in Photoshop 5.0. Guides were introduced in Photoshop 4.0

BMP is a standard Windows image format on DOS and Windows-compatible computers. BMP format supports RGB, Indexed Color, Grayscale, and Bitmap color modes, and does not support alpha channels.

You can specify either Microsoft® Windows or OS/2® format and a bit depth for the image. For 4-bit and 8-bit images using Windows format, you can also specify RLE compression.

Tagged-Image File Format (TIFF) is used to exchange files between applications and computer platforms. TIFF is a flexible bitmap image format supported by virtually all paint, image-editing, and page-layout applications. Also, virtually all desktop scanners can produce TIFF images.

TIFF format supports CMYK, RGB, Lab, indexed-color, and grayscale images with alpha channels and Bitmap-mode images without alpha channels. Photoshop can save layers in a TIFF file; however, if you open the file in another application, only the flattened image is visible. Photoshop can also save annotations, transparency, and multiresolution pyramid data in TIFF format.

PICT format is widely used among Mac OS graphics and page-layout applications as an intermediary file format for transferring images between applications. PICT format supports RGB images with a single alpha channel, and indexed-color, grayscale, and Bitmap-mode images without alpha channels. PICT format is especially effective at compressing images with large areas of solid color. This compression can be dramatic for alpha channels with their large areas of white and black.

When saving an RGB image in PICT format, you can choose either a 16-bit or 32-bit pixel resolution. For a grayscale image, you can choose from 2, 4, or 8 bits per pixel. In Mac OS with QuickTime installed, four JPEG compression options are available.

**Note: In ImageReady, PICT format is supported in Mac OS only.

For the web, these are the most common file types:

Graphics Interchange Format (GIF) is the file format commonly used to display indexed-color graphics and images in hypertext markup language (HTML) documents over the World Wide Web and other online services. GIF is an LZW-compressed format designed to minimize file size and electronic transfer time.

GIF format preserves transparency in indexed-color images; however, it does not support alpha channels.

Joint Photographic Experts Group (JPEG) format is commonly used to display photographs and other continuous-tone images in hypertext markup language (HTML) documents over the World Wide Web and other online services. JPEG format supports CMYK, RGB, and Grayscale color modes, and does not support alpha channels. Unlike GIF format, JPEG retains all color information in an RGB image but compresses file size by selectively discarding data.

A JPEG image is automatically decompressed when opened. A higher level of compression results in lower image quality, and a lower level of compression results in better image quality. In most cases, the Maximum quality option produces a result indistinguishable from the original.

Developed as a patent-free alternative to GIF, Portable Network Graphics (PNG) format is used for lossless compression and for display of images on the World Wide Web. Unlike GIF, PNG supports 24-bit images and produces background transparency without jagged edges; however, some Web browsers do not support PNG images. PNG format supports RGB, indexed-color, grayscale, and Bitmap-mode images without alpha channels. PNG preserves transparency in grayscale and RGB images.

For use with Illustrator and other page layout programs, use these file types:

Encapsulated PostScript (EPS) language file format can contain both vector and bitmap graphics and is supported by virtually all graphic, illustration, and page-layout programs. EPS format is used to transfer PostScript-language artwork between applications. When you open an EPS file containing vector graphics, Photoshop rasterizes the image, converting the vector graphics to pixels.

EPS format supports Lab, CMYK, RGB, Indexed Color, Duotone, Grayscale, and Bitmap color modes, and does not support alpha channels. EPS does support clipping paths. Desktop Color Separations

(DCS) format, a version of the standard EPS format, lets you save color separations of CMYK images. You use DCS 2.0 format to export images containing spot channels. To print EPS files, you must use a PostScript printer.

Portable Document Format (PDF) is a flexible, cross-platform, cross-application file format. Based on the PostScript imaging model, PDF files accurately display and preserve fonts, page layouts, and both vector and bitmap graphics. In addition, PDF files can contain electronic document search and navigation features such as electronic links.

Photoshop and ImageReady recognize two types of PDF files: Photoshop PDF files and Generic PDF files. You can open both types of PDF files; however, you can only save images to Photoshop PDF format.

Photoshop PDF files are created using the Photoshop Save As command. Photoshop PDF files can contain only a single image.

Photoshop PDF format supports all of the color modes and features that are supported in standard Photoshop format. Photoshop PDF also supports JPEG and ZIP compression, except for Bitmap-mode images, which use CCITT Group 4 compression.

Generic PDF files are created using applications other than Photoshop, such as Adobe Acrobat and Adobe Illustrator, and can contain multiple pages and images. When you open a Generic PDF file, Photoshop rasterizes the image.

For use with video production and animation, use these file types:

PIXAR format is designed specifically for exchanging files with PIXAR image computers. PIXAR workstations are designed for high-end graphics applications, such as those used for three-dimensional images and animation. PIXAR format supports RGB and grayscale images with a single alpha channel.

TGA (Targa®) format is designed for systems using the Truevision® video board and is commonly supported by MS-DOS color applications. Targa format supports 24-bit RGB images (8 bits x 3 color channels) and 32-bit RGB images (8 bits x 3 color channels plus a single 8-bit alpha channel). Targa format also supports indexed-color and grayscale images without alpha channels. When saving an RGB image in this format, you can choose a pixel depth.

QuickTime Movie (.mov) format is a cross-platform format used for time-based data, such as video and audio. In ImageReady, you can save animations as QuickTime movies and open existing QuickTime movies as animations in order to optimize them for the Web. To save as a QuickTime Movie, Export rather than Save As.

Note: In Windows, QuickTime Movie format is visible in the Files of Type pop-up menu only when QuickTime is installed on your computer.