There are a variety of file formats used to encode digital images. The most popular are .JPG (or .JPEG), .TIFF, .GIF and .PNG. You have probably seen all these file extensions at some point. Each format has unique characteristics that make it fitting for particular uses. Typically it’s the way the file format handles compression and the number of colors in the image.
Compression
This deals with the file size. The more compressed the image the smaller the file. The downside is that image quality will suffer. There are two types of compression, lossy and lossless. Lossy compression reduces the size of the image by discarding image detail. Lossless compresses the image without discarding any detail, but the file sizes are larger.
Number of colors
The number of different colors that make up an image can vary greatly. The simplest may only have one of two colors (a good example of these would be logos) while the more complex (like digital photos) contain millions. Certain file types, like .GIF, are better suited for images with less color while others, like .JPEG, all well suited for images with millions of colors.
.JPG (or.JPEG)
Stands for Joint Picture Experts Group. This is the most popular file type for digital photography. It handles millions of colors very well and allows for various levels of lossy compression. It is also the most widely used file format on the web.
.TIFF
Stands for Tagged Imaged File Format. It is generally used for professional photography, print publishing and graphic design. This format uses loseless compression so the files are usually very large.
.GIF
Stands for Graphics Interchange Format. This file type uses loseless compression and is generally used for images with less than 256 colors, like icons or logos. It works well if the image uses “flat” colors that don’t contain gradients, like clipart.
.PNG
Stands for Portable Network Graphics. This is a newer file format similar to a .GIF but it supports more colors. It also takes advantage of patterns in the image that can be used to compress the file except the compression is 100% reversible, so the image quality isn’t affected.