| |
| |
| File Formats: |
| |
|
Photoshop Format (PSD):
|
|
Photoshop format (PSD) is the default file format and the only format that supports most Photoshop features besides the Large Document Format (PSB). Due to the tight integration between Adobe products, other Adobe applications like Adobe Illustrator, Adobe InDesign, Adobe Premiere, Adobe After Effects and Adobe GoLive can directly import PSD files and preserve many Photoshop features. For more information, see Help for the specific Adobe applications; also see Saving image for use in video and Saving image for use in motion graphics. |
 |
 |
|
Encapsulated PostScripts
(EPS): |
| 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 but does not support alpha channels. EPS does support clipping paths. |
| |
|
|
|
Desktop Color Separations (DCS):
|
| Desktop Color Separations (DCS) format, a version of the standard EPS format, lets you save color separations of CMYK image. You use DCS 2.0 format to export image containing spot channels. To print EPS files, you must use a PostScript printer.
Photoshop uses the EPS TIFF and EPS PICT formats to let you open image saved in file formats that create previews but are not supported by Photoshop (such as QuarkXPress®). An opened preview image can be edited and used like any other low-resolution file. An EPS PICT preview is available only in Mac OS.
Note: EPS TIFF format and EPS PICT format were more relevant for use in earlier versions of Photoshop. The current version of Photoshop includes rasterization features for opening files that include vector data. Desktop Color Separations (DCS) format is a version of the standard EPS format that lets you save color separations of CMYK image. One can use DCS 2.0 format to export image containing spot channels. To print DCS files, you must use a PostScript printer. |
|
|
|
|
| Graphics
Interchange Format (GIF):
|
|
Graphics Interchange Format (GIF) is the file format commonly used to display indexed-color graphics and image 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 image; however, it does not support alpha channels.
|
|
|
|
|
|
Interchange File Format (IFF):
|
|
Interchange File Format is available through an optional plug-in. It is a general purpose data storage format that can associate and store multiple types of data. IFF is portable and has extensions that support still-picture, sound, music, video, and textual data. The IFF format includes Maya IFF and IFF (formerly Amiga IFF). |
|
|
|
|
Joint Photographic Experts
Group (JPEG): |
Joint Photographic Experts Group (JPEG) format is commonly used to display photographs and other continuous-tone image 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.
|
|
|
|
|
| Portable Document Format (PDF): |
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. PDF supports 16-bit-per-channel image. Adobe Acrobat also has a Touch Up Object tool for minor editing of image in a PDF. For more information about working with image in PDFs, see Acrobat Help.
Note:The Touch Up Object tool is mainly for last-minute revisions to image and objects. It's best to do image editing in Photoshop before saving as PDF.
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 image 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 (except Multichannel mode) and features that are supported in standard Photoshop format. Photoshop PDF also supports JPEG and ZIP compression, except for Bitmap-mode image, which use CCITT Group 4 compression.
|
|
|
Are created using applications other than Photoshop, such as Adobe Acrobat and Adobe Illustrator, and can contain multiple pages and image. When you open a Generic PDF file, Photoshop rasterizes the image. |
|
|
|
|
|
|
Portable Network Graphics (PNG): |
|
Developed as a patent-free alternative to GIF, Portable Network Graphics (PNG) format
is used for lossless compression and for display of image on the Web. Unlike GIF,
PNG supports 24-bit image and produces background transparency without jagged edges;
however, some Web browsers do not support PNG image. PNG format supports RGB, indexed-color,
grayscale, and Bitmap-mode image without alpha channels. PNG preserves transparency
in grayscale and RGB image. |
|
|
|
|
|
Scitex Continuous Tone (CT): |
|
Scitex Continuous Tone (CT) format is used for high-end image processing on Scitex computers. Contact Creo to obtain utilities for transferring files saved in Scitex CT format to a Scitex system. Scitex CT format supports CMYK, RGB, and grayscale image and does not support alpha channels.
CMYK image saved in Scitex CT format often have extremely large file sizes. These files are generated for input using a Scitex scanner. image saved in Scitex CT format are printed to film using a Scitex rasterizing unit, which produces separations using a patented Scitex half toning system. This system produces very few moiré patterns and is often demanded in professional color work--for example, ads in magazines. |
|
|
|
|
|
Tagged Image File Format (TIFF): |
|
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 image. TIFF documents can have a maximum file size of 4 GB. Photoshop CS supports large documents saved in TIFF format. However, most other applications and older versions of Photoshop do not support documents with file sizes greater than 2 GB. For more information on saving large documents in TIFF format, see Saving large documents (Photoshop).
TIFF format supports CMYK, RGB, Lab, indexed-color, and grayscale image with alpha channels and Bitmap-mode image 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 multi-resolution pyramid data in TIFF format. |
|
|
|
|
| |
|
File Compression: |
| |
|
Many file formats use compression to reduce the file size of bitmap image. 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. LZW is most useful for image with large areas of single color. |
|
JPEG: Lossy compression; supported by JPEG, TIFF, PDF, and PostScript language file formats. Recommended for continuous-tone image, 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 (Photoshop) or 0 and 100 (ImageReady) 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 image; 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 image that contain large areas of single color. |
|
PackBits (ImageReady): Lossless compression that uses a run-length compression scheme; supported by the TIFF file format in ImageReady only. |
|
|
|
|
|
|
| |
|
Tips: |
| |
TIP 1: Use GIF and JPG for online publishing. Although other formats for online publishing are in development, at present GIF and JPG are the standards. Use EPS and TIFF for print publishing. If all your printing is sent to your desktop printer, you may be able to use other formats including CGM and PCX with acceptable results; however, for high-resolution output EPS and TIFF will provide the least hassles and the best quality. They are the standards for high-resolution printing. In addition to the formats in the chart, below, there are proprietary graphics file formats. These are bitmap or vector formats used by specific graphics programs.
TIP 2: Although some desktop publishing software will recognize the more common formats such as PSD from Adobe Photoshop (bitmap) or CDR from CorelDRAW (vector) it is generally best to convert these image to TIF or EPS or other common graphics file formats. This simple chart outlines the best use for several common formats. Match the format to your job either by starting with graphics in that format or by converting other artwork to the desired format. Even if your service bureau or printer requires graphics in a different format (usually TIFF or EPS) always save your files in the native format of your graphics software in addition to the format needed for printing. If you later need to edit the file, resize, resample, save in additional formats, etc., you and your graphics program will have fewer problems working with the file in its native format.
TIP 3: When creating image to be used on the Web in GIF or JPG format, editing and resizing is best done on the native file formats. GIF image don't resize well so if you need to resize, resize the original then export as a new GIF. Because JPG uses a lossy compression, data is lost each time you open, edit, and re-save the file. Edit the original file in its native format then export as a new JPG. |
|
|
|
|
| |
|
