File Formats 101: What do they all mean?

File formats 101: What do they all mean?

.jpg .gif .png .pdf .tif .bmp .psd .psp .raw

By Yetta Blair

Anyone working on a computer, which basically means nearly everyone, has a basic working knowledge of file formats.  If you are like most however, this knowledge means you sort of kind of have a feeling of which file format you should use, but are not exactly sure how it works and why it should be your choice.

With this in mind, I created a cheat sheet, so to speak, of the most highly used file formats and hints of when to use them.

.jpg – Great to use for web sites and email. This file format is optimized for photographs and compresses continuous-tone images that contain many colors down to a size that can be downloaded quickly on the internet. This is the format of choice for nearly all photographs on the web. You can achieve excellent quality even at rather high compression settings.  However, the downside to this format is that compressing the image too much will cause it to look jagged.  The JPG file extension is used interchangeably with JPEG.  JPEG stands for “Joint Photographic Experts Group” who created the standard.  JPG files can be opened by most image editing software from Microsoft Paint to Adobe Photoshop.

.gif –  Another good file type for the Internet and emailing. GIF’s do a great job of compressing images and making them suitable for fast downloads. If your image has fewer than 256 colors and contains large areas of uniform color, GIF is your choice. The files will be small yet perfect and is well suited for some cartoons or clip art. Do NOT use GIF for photographic images, since it can contain only 256 colors per image. An added bonus is that GIF images can be placed on a web page with a clear background, so you can layer them. However, the downside is that sometimes the artwork has a sharp, unattractive border when the image's background is invisible. When this happens, try the PNG format. GIF stands for “Graphics Interchange Format”.

.png – “Portable Network Graphics”. If you want to display a photograph exactly without loss on the web, PNG is your choice. Its strategy is similar to that of GIF, but it supports 16 million colors, not just 256. PNG is the only lossless format that web browsers support. (A lossless compression algorithm discards no information. All image information is restored when the file is decompressed during viewing. In contrast, lossy algorithms accept some degradation in the image in order to achieve smaller file size.)PNG’s are usually larger in file size than jpg and gif files but they allow people to save artwork to be layered on web pages or other artwork without any sharp or disruptive border. PNG’s are extremely versatile, but they usually result in larger files and longer download times.

.eps – "encapsulated post Script". EPS is used in vector-based images in Adobe Illustrator. An EPS file can contain text as well as graphics. Professional printers and printable advertising media, like a magazine, will typically ask that the artwork be saved as an EPS file but a TIF or PDF are also good choices.

.tif – The TIF is an image format file for high-quality graphics. TIF files are also called TIFF, which stands for “Tagged Image Format File .TIF files originally only supported black and white. However, the update in 1988 added a color palette. Now owned by Adobe, the .TIF format is used for high color-depth images. TIF files can be converted to JPEG, GIF or PDF format. Printers and advertisers will often permit final artwork to be designed in a TIF. TIF is not widely supported by web browsers, and should be avoided for web use.

.pdf – "portable document format", Adobe's native file format that is read by a program called Adobe Acrobat. Most computer users have Acrobat on their system, if they don't, they can download Acrobat Reader for free. The PDF has a wide range of uses, including a lot of usage on web, and they can even be used for printing when saved as a high resolution PDF.

.bmp – is an uncompressed proprietary format and there is really no reason to ever use this format.  BMP stands for “Bitmap”.

.psd, .psp – are proprietary formats used by graphics programs. Photoshop's files have the PSD extension, (PSD stands for Photoshop Document) while Paint Shop Pro files use PSP (PSP stands for Paint shop pro). These are the preferred working formats as you edit images in the software, because only the proprietary formats retain all the editing power of the programs. These packages use layers, for example, to build complex images, and layer information may be lost in the nonproprietary formats such as TIF and JPG. However, be sure to save your end result as a standard TIF or JPG, or you may not be able to view it in a few years when your software has changed.

.raw – The RAW file format is digital photograhpy’s equivalent of a negative in film photography: it contains untouched “raw” pixel information straight from the digital cameras sensor. Use RAW only for in-camera storage.  Copy or convert to TIFF, PNG, or JPG as soon as you transfer to your PC. You do not want your image archives to be in a proprietary format since you can’t be sure you will be able to read that format in 5, 10 or 20 years.  Most believe that JPG is the format most likely to be readable in 50 years. Thus, it is appropriate to use RAW to store images in the camera but be sure to create a TIFF, PNG or JPG, for archival storage.