Graphic File Types

Graphic Image File format. GIF87a was the original web graphic file format. The current version, GIF89a, supports 1-bit transparency, comments, and simple animation.

GIF is your best web option for images with flat, solid colors -- the sort of images you normally create in vector drawing programs like Illustrator or FreeHand. Of course we'd love to put them on the web as vectors, but for the most part that's not possible (but see SVG in this chart). So we use GIF, a raster format, for those kind of images online.

GIF is rarely a good choice for non-Web use.

Cons: indexed color only (typically 8-bit or less), which means you often have to permanently throw away image data prior to conversion -- although the file format itself, and its LZW compression algorithm, are lossless. Note that this is true despite the fact that in Photoshop's Save for Web options for GIF we see a "lossy" checkbox -- that just rearranges the pixel patterns slightly to enhance the compression. GIF being a "lossless" format means that, unlike with JPEGs (a lossy format), we could possibly open a GIF repeatedly, edit it, and re-save it back out again without necessarily degrading it. (Of course, editing GIFs or any other file format that's primarily designed for export isn't usually ideal; it's generally best to go back to the master file -- often a PSD -- for editing, and then re-export the GIF or JPEG.)

Joint Photographic Experts Group. Actually a family of file formats; usually refers to JFIF JPEG.

For web, digital camera storage, and stock photo dissemination. (By the way, this latter use is counter-intuitive, since it's a lossy format and stock photos are often intended for high-end prepress work; but in this kind of use the files are so huge, and the compression applied so minimal, that there's no significant data loss.) But for everyday use -- which generally means in web development -- the lossiness is a major issue. The tradeoff is between file size and quantization artifacts.

Typically JPEGs are 24-bit RGB files. There are many variants and choices to be made in exporting JPEGs. Alternatives to Photoshop's built-in "Save for Web" JPEG creation include a few third-party JPEG export modules, such as from HVS and BoxTop. They give you more control in some ways, and less in other ways, than what's built-in to Photoshop or its companion webdev program, ImageReady.

Portable Network Graphics. Recent substitute for GIFs (and some JPEGs) online. Many technical advantages over GIFs -- for example, multi-bit transparency map, metadata for color management (gamma and profile) -- but also larger file sizes. Very spotty browser support so far, so it hasn't really caught on; patents on LZW (which triggered the development of PNG) are expiring anyway. When most people have broadband connections, and most installed browsers reliably support the full range of PNG features, this will probably become a significant file format. But don't hold your breath.

Scalable Vector Graphics. Wouldn't you love to put flat-color or other simple graphics (like logos and diagrams) online in compact, scalable vector form? The W3C has approved this Adobe-sponsored XML derivative. Hasn't caught on; no real browser support, although Adobe offers a free viewer. It's the classic web development chicken-and-egg problem. The only vector format widely used at present is Flash, but it's not really a substitute (you wouldn't create a Flash file just to hold a non-animated scalable logo, for example).

Tagged Image File Format. Raster only. Most widely used format for photos in prepress world (although EPS is also used for this purpose). Cross-platform.

TIFF variants: Compressed (lossless LZW) or uncompressed; RGB or CMYK.

Pros: most reliable, widespread format for raster data. Can hold almost any resolution, color scheme, etc. I like this format because it's uncomplicated and (unlike EPS) rarely causes trouble.

Cons: can't hold vector data; large, and sometimes slow to print; Mac and PC have slightly different flavors (although most Mac apps support both); many nonstandard "improved" versions floating around.
Variations: TIFF IT (widely used by ad agencies), etc.

A .ps is a simple text file, and there are basically three things you can do with it: dump it to a printer; convert it to PDF via Acrobat Distiller; or -- if you're a PostScript programmer -- edit it directly in a text editor. (I'm not a PostScript programmer but, being rather geeky for a creative type, I've been able to make some simple, useful changes within .ps files on occasion. You have to be careful though -- one tiny mistake and the whole thing may not work.)

Encapsulated PostScript. EPS is essentially a PostScript file in an "envelope." It usually -- but not always -- includes a rasterized preview in TIFF or PICT, plus some metadata. EPS was originally the native format of Illustrator.

Like virtually all "vector" file formats, EPS can hold raster data too; and it's the only way to import photos with clipping paths (which is to say, raster data surrounded by a vector) into Quark and some other programs. EPS files are mostly exported from a "creation" program like Illustrator, FreeHand, or Photoshop, and then placed in a layout program like Quark or InDesign... that is to say, EPS files usually aren't edited directly. But if you need to, modern apps can sometimes open them... provided (1) the EPS isn't too old (the format has evolved) and (2) you're feeling lucky. Sometimes the data is editable; sometimes, even if you can crack open the file, it turns out to be in a form where editing is impractical. Moral: always save the master files used to create your export files!

Pros: can contain clipping path, true font data, various kinds of metadata; widely accepted.

Cons: previews optional & nonstandard; sometimes contains insufficient data but you wouldn't know because the preview can be misleading; file format has evolved so is nonstandard; may only print properly to PostScript printers; can be flaky at times.

Adobe Illustrator's regular application format originally was EPS. Illustrator's current ".ai" format has been extended to include extra features that newer versions of the program offer, but the original .eps file format (with, unfortunately, variations that reduce compatibility) has been kept as the "generic" version of the format. See EPS.

Portable Document Format, also known as "Adobe Acrobat format." Slightly editable form of PostScript (that is, editable with Acrobat without having the authoring app). More stable and universal than other forms of PostScript.

Adobe moving towards this as a universal file format; for example, Photoshop PDFs can contain layers, Acrobat 6 can work with them, etc.

Prepress variants of PDF with more specific specs:
PDF/X-1a
PDF/X-3

No metadata whatsoever, not even the most basic facts about the image such as its size, color mode, etc. Used by Photoshoppers when they have no idea what a file type is and are desperate to crack it open somehow. I assume this can't be the same as the "Raw" format that some high-end digital cameras offer (do they really mean TIFF?), but I'm not clear on what the difference between Photoshop's "raw" and a digital camera's "raw" actually is. (If you know, please tell me. Thanks.)