File extensions and file compression

File Extensions.

When saving a file on programs such as Adobe Photoshop, there are several different types of of files it can be saved as. Different file extensions have different properties, like:

JPEG - This does not have the best quality, but fairly good compression. It is a 'lossy' format, meaning it will lose quality each time it is saved. It is 24-bit colours (16.4 million colour possibilities). This format is still widely used because it's simple, anybody can view it, and it's small file size means it is quick to upload to websites and quick to load when viewing the website.

PNG - Improvement on the GIF and JPEG formats. Low compression, but it is a loss-less format means it retains it's full image quality no matter how many times it is saved. Supports 48-bit colours (1 billion colour possibilities). Does not support CMYK, so commercial printers cannot print this file type.

There are a lot more file extensions available for use, these include:

• PSD
• GIF
• TIFF
• EPS
• PDF

File Compression.

File compression does a number of things. The main function of compressing a file is to reduce the size of the file (e.g. from 1 GB to 78 MB) depending on the type of compression. However, in order to acheive high compression, image quality must be sacrificed.

If it is going to take a few days/weeks to complete an image, it is generally a good idea to save as a loss-less format while working on it and when the image is complete then save it as a format such as JPEG (unless it specifically has to be a different type of file).