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Image file types

There are so many. How do they differ?


A GIF or Compuserve GIF image file is frequently used in web design. It works best with images that don't have a large range of colors.
A GIF or Compuserve GIF image file is frequently used in web design. It works best with images that don't have a large range of colors.

We have already examined JPEG, TIFF and RAW under "Choosing a file format." Other image file types you'll come across include the common ones listed below. They are identified by their file extension (e.g. A GIF file type has ".gif" as its extension, as in "portrait.gif"):

BMP (Bitmap) or RLE or DIB - A basic, uncompressed file format created by Microsoft that is mainly used in Windows-based applications. Channels and layers cannot be saved in this format.

DNG - (Digital Negative) Adobe introduced DNG as a single raw processing solution for handling RAW files from multiple camera models and manufacturers. Adobe promotes DNG as an open standard for raw files created by individual camera models to help ensure that photographers will be able to access their files in the future.

EPS (Encapsulated Post-Script) or Photoshop EPS - This format, normally employed in the print process, is used in transferring vector or bitmap images into an image-editing program such as Illustrator, PageMaker or QuarkExpress, or from one application to another.


GIF or CompuServe GIF - (Graphics Interchange Format) is a moderately-compressed image file format that is constrained to a maximum of 256 colors, generally making it a poor choice for your digital images. When it was created, most computer video cards were able to display no more than 256 colors. It is used mainly on the internet for graphic images that don't require subtle or gradual change in tones. It was created for compressing and viewing online images from the CompuServe network, and is also known as a "CompuServe GIF." An advantage to GIF is that it is a format easily interpreted by computers, although it is unsuitable for complex images such as photographs.

PCX - A format that has been around for a while, and has a number of variations. Created by ZSoft for PC Paintbrush, it is similar to the BMP filetype, so that most image-editing software supports it. It is mainly used on Windows-based computers, but its simplicity makes it compatible with Mac and Linus platforms as well. It has moderate lossless file compression capabilities.

PDF - Its name is derived from "Portable Document Format," and is an image file type created in Adobe PhotoShop that results in pictures that are viewable with Adobe Acrobat, so someone (Mac or PC-user) who doesn't have PhotoShop can still view the image. It is often used in forms creation and for documents that require their layout, fonts and images to appear unchanged from the original.

Most image-editing software supports a PCX file, which has moderate lossless file compression capabilities.
Most image-editing software supports a PCX file, which has moderate lossless file compression capabilities.

When an image is edited as a PSD file (essentially PhotoShop's version of a TIFF file), it must be converted to another image file type before use.
When an image is edited as a PSD file (essentially PhotoShop's version of a TIFF file), it must be converted to another image file type before use.

PICT - Although used mainly to transfer images between programs on a Mac computer, it is also supported by several PC applications. PICT has been largely replaced by PDF.

PNG - Pronounced "ping," it stands for "Portable Network Graphic" format, and is characterized by its ability to compress image files without a big quality reduction. PNG was developed to replace GIF and JPEG formats on the internet, but it doesn't appear to have caught on yet to a great extent, although it seems to be slowly gaining in popularity. It is compatible with both Apple Macintosh and Windows computers.

PSD (PhotoShop Document) and PDD - created in and used only in Adobe Photoshop. This format is slightly compressed when compared with other image file formats, and contains data on editing that has been done to the image. A PSD file is essentially PhotoShop's version of a TIFF file, and allows the highest flexibility manipulating images in Photoshop. It lets you save a picture you are working on with its layers, channels and other image-editing data intact. (Note that increasing the number of layers and channels within the image increases the file size.) PSD files must be converted to another image file type before use.


IMAGE-EDITING FILE TYPES

Some image-editing applications like Adobe PhotoShop have their own file types for purposes of creating and saving presets (groups of settings that can be shared across Adobe Creative Suite components, including InDesign, Illustrator, Photoshop, and Acrobat) for repeated use on more than one image file. PhotoShop comes with its own libraries of preset brushes, swatches, gradients, styles, patterns, contours, custom shapes and preset tools. You can, for example, save a set of brush options as a preset so you can quickly access brush characteristics you use frequently.

PhotoShop's list includes the following file extensions:

  • .abr - Brush set;
  • .aco - Color swatch;
  • .act - Optimized colors;
  • .acv - Curve;
  • .ado - Duotones, quadtones, tritones;
  • .asl - Layer style set;
  • .atn - Action set;
  • .csh - Custom shapes;
  • .grd - Gradient set;
  • .iros - Optimized output settings
  • .irs - Optimized settings;
  • .pat - Pattern set;
  • .sch - Contours

The above library of Brush presets appears in Adobe PhotoShop's
The above library of Brush presets appears in Adobe PhotoShop's "Preset Manager."


Related topics...

Choosing a file format

Image resolution