File Formats

[ricktas]

There are a vast array of file formats that digital images can be created in or converted to.

This thread is about identifying those formats and providing some detail about each format.

If you wish to add to this thread, please do so, but please keep to the following formatting

Extension - the file type use by files
Description - Describe the file type

So let's get started.

Probably the most common file type for digital images is:

JPG (sometimes called JPEG)

JPG (Joint Photographic Group) was developed as a way to compress image files for transmission digitally. The Joint Photographic Experts Group created the JPG standard in 1992.

JPG is a lossy format, meaning that data within the file is lost as it is saved in the JPG format. Once this data is lost from the file, it cannot be recovered. If you save a JPG file over and over, eventually as it loses data each time, you will start to see pixelation in the resultant image. This often appears as 'blockiness' in areas of single or similar colour (ie blue skies). JPG files are created in the sRGB colour-space. The benefits of JPG are their file-sizes. An image file can be saved into quite a small file size using JPG and have no obviously noticeable degradation of image quality, allowing the file to be easily transmitted digitally.

Having said this, some edits to JPG files do not result in loss of data. Rotating, cropping or flipping an image for instance.

Due to their lossy nature, JPG files are not the best files to perform edits on. You are best working on an image in another high quality and non-lossy file type and once editing is complete, then save a copy of the finished image as a JPG file.