Graphics File Formats
Adobe Photoshop Document (PSD)
PSD files are the native file format for Adobe Photoshop software, which can only be opened by Photoshop, along with a few other pieces of Adobe software. These files can contain either graphics, with multiple layers, or photos, and are used by both designers and printers. PSD files are a type of raster format, meaning that they are made up of large amounts of tiny dots. Due to this, if the file is increased or decreased in size significantly, then the quality of the image will be reduced. They can also be exported to a number of other file formats, including JPG, PNG and GIF, making them useful for web design.
Adobe Illustrator (AI)
Adobe Illustrator files are, as the name suggests, created by Adobe Illustrator software. They can contain mult-layered graphics, which again, as with PSD files, can be exported to numerous other file formats, including JPG, PNG and GIF. Unlike PSD files, these are vector based, meaning that they are very scalable with no loss of quality. Due to this they are ideal for producing graphics such as illustrations, banners or logos. AI files are also popular with designers and printers.
Joint Photographic Experts Group (JPG or JPEG)
The JPG file format is optimised for use with photographs and similar continuous tone images. It is a standard format that can be opened by the majority of design applications available today. As with PSD files, this is a raster format, so the images will lose quality when scaled. It uses compression techniques to reduce the file size, with the amount of compression used being user defined. This makes it an ideal format for use on the web and in e-mails. Compression does however, have the effect of reducing the image quality, the more compression that is used, the greater the loss of quality. This format also does not support transparency.
Graphics Interchange Format (GIF)
GIF files are a low-resolution raster format, which as with JPGs, are ideal for use on the web and in e-mails. They are also widely supported by most web browsers. Unlike JPGs, this format does support transparency, however, GIFs can only support up to 256 colours in any one image, from a choice of over 16 million, which means they are not good for photographs. It is possible though to add animation to a GIF file for use on the web.
Portable Network Graphics (PNG)
PNG files are the third raster format, which are ideal for use on the web. This is a low-resolution format that supports transparency, with a fast loading time in a web browser and has no loss of quality. The advantage PNGs have over GIFs is that they are not limited to 256 colours in any one image, however, some older versions of web browsers do not support them.
Tagged Image File Format (TIF or TIFF)
TIF files are the standard format for high quality images and the most widely supported, designed to be hardware and operating system independent. Although large in size, they are considered to be the most reliable format, producing better quality images than both JPG and PNG. However, this format is not vector based, so the quality of the image is lost if they are scaled.
Encapsulated Postscript (EPS)
EPS files can contain both raster (bitmap) or vector based graphics. When they contain vector based graphics they are scalable with no loss of quality, which is a contributing factor in making this the preferred format with designers for transferring graphics from one piece of software into another. They can be used in both Adobe Photoshop and Illustrator, mentioned above, along with numerous other applications.
Scalable Vector Graphics (SVG)
The Bitmap file format was invented by Microsoft, for use within the Microsoft Windows operating system. They can also be used on a MAC. The big disadvantage with this format is that they are uncompressed and therefore can be very large. Due to this its uses are limited. BMP files also don't scale very well due to the loss of image quality. The only advantage is that they are widely available to all software that runs on Microsoft Windows.
Portable Document Format (PDF)
Portable Document Format is an open source file format that was developed by Adobe Systems. It is useful for transferring design work between designers or from a designer to a client, as they preserve the format of the items they contain. This may be layered graphics, originally created in, for example, Photoshop and Illustrator, or the layout and fonts used in an InDesign document. These files can be opened by anyone using the free Adobe Reader software.