[Definition] File Formats

[Doug Nelson]

TIF (or TIFF) - Tagged Image File format
The best non-proprietary format for photographic images. TIF is a "lossless" format, meaning no data is thrown away during compression. There are many different flavors of TIF, but most modern editors read them all, making custom choices pretty much irrelevant. TIF files support millions of colors, up to 16 bits per color plane, and most color modes (RGB, CMYK, LAB, HSV, etc.). TIF files are an appropriate choice for archiving originals.

JPG (or JPEG) - Joint Photographic Experts Group
JPG is a "lossy" file format, meaning data is discarded to save space. The amount of data that it discards is determined by the amount of compression selected. JPG files support millions of colors, but only the RGB color space. JPG files are suitable for storing intermediate copies, but not originals. Editing should not be performed on JPG files, as further loss will be incurred. Rather, they should be converted to a lossless format first, then converted back if necessary.

GIF - Graphic Interchange Format
GIF files are both lossy and only support 256 colors. They also require the use of their own color space, called "indexed". For these reasons GIF files are virtually useless for photographic images.

[Doug Nelson]

EPS - Encapsulated Postscript
EPS is a vector-based (lines/curves/math) format. The "encapsulated" nature of this format allows it to include photographic file data, but only as an internal attachment. There are no advantages in using this file for photographic purposes, and several disadvantages.

[G. Couch]

PNG - (Portable Network Graphics)

The PNG file format was designed to replace GIF. It supports, indexing, grayscale and RGB. Unlike GIF, it uses a lossless compression. PNG supports transparency but not multiple images in the same file (animation).

[Doug Nelson]

I'll add here that PNG supports both lossless and lossy compression, and hasn't caught on because it is primarily aimed at the web, but no two browsers support the same subset of PNG features, and no browser supports all PNG features.

PNG has very little use for retouching and restoration.

[john_opitz]

How about RAW format Mr. Nelson. What you get from digital cameras. That's the format I like to use. Just like how I like my steak.

[d_kendal]

here's a good source of info for image file types: http://www.wfu.edu/~matthews/misc/gr...s/formats.html

- David

[arcadhia]

Thanks Kendal, today I'm a better person