Summary of Central's most
commonly used image formats
EPS
Encapsulated PostScript® (EPS) can be in either vector format (mathematically defined lines & curves) or bitmap format (technically called raster images—use a grid of colours known as pixels to represent images). When you open an EPS file containing vector art in Photoshop, it is rasterized—the vector artwork converted into a bitmap image. An InDesign page can be saved as an EPS and be exported to other programs such as Photoshop and Illustrator.
Desktop Colour Separations (DCS) format, a version of the standard EPS format, lets you save colour separations of CMYK or multichannel files. You use DCS 2.0 format to export images containing spot channels.
To print EPS and DCS files, you must use a PostScript printer.
Programs in which EPS can be used are: Adobe InDesign, Adobe Illustrator, Adobe Photoshop and QuarkXPress.
TIFF/TIF
Tagged Image File Format (TIFF) is especially versatile for use with PostScript and non-PostScript printing devices. It is based on reducing an image to a bitmap representation of the artwork, very much like a drawing made using the squares on graph paper.
Programs in which TIFF can be used are: Adobe InDesign, Adobe Illustrator, Adobe Photoshop, QuarkXPress and Microsoft Office applications.
GIF
GIF is one of many formats used for Web pages. The GIF format uses 8-bit colour and efficiently compresses solid areas of colour while preserving sharp detail, such as that in line art, logos, or illustrations with type.
GIF supports background transparency and background matting, in which you blend the edges of the image with a Web page background colour/pattern
GIF is supported by most Web browsers.
JPEG/JPG
JPEG supports 24-bit colour and preserves the broad range and subtle variations in brightness and hue in images. However, JPEG compresses file size by selectively discarding data. Hence, JPEG files provide quality colour images that may not be very sharp, depending on the levels of resolution and compression.
JPEG format does not support transparency, i.e. when a JPEG image is placed into a Web page you will see the image in a box.
JPEG is supported by most Web browsers.
In terms of printing, JPEG is not an ideal format to use because the files are compressed, causing data loss and less detailed images.
Portable Document Format (PDF) is an electronic file format standard that allows the conversion of any type of electronic document (Word, Excel, Photoshop, InDesign, etc.) to a proprietary format which allows:
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- Significant savings in file size. Everything is compressed with controllable loss of quality.
- A file that can be read by all types of computers.
- A true-to-the-original reproduction of the original file layout, colours and fonts. It does not require any of the applications the original used nor any of the fonts utilized, if embedded, to be viewed.
- PDF files can also be edited with Adobe Acrobat software.
Other uses of Acrobat PDF files:
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- For presentations.
- For delivering final reliable output files to your print shop when created with proper settings.
- For revisions and comments.
- For automatically creating offline copies of Internet web sites.
- Producing electronic versions of books or publications for easy distribution and re-use.