File Types

There are a number of file types commonly used with digital photos. Most of these formats offer some form of compression - either lossy or lossless. Lossless compression reduces the size of a file without reducing the amount of information in the file. Lossy compression further reduces the file size, but also reduces the quality of the image. Resaving the same file in a lossy format leads to image degradation. Although it is usually best to work on a copy of a file instead of the original, this is particularly true for lossy formats. Files that are being edited should be saved in a lossless format with only the final result saved in a lossy format.

JPEG is the most common format for photos or any image with tonal transitions, especially on the web. JPEG is a lossy format that allows users to choose different compression settings when saving the file, which gives a trade-off between file size and image quality. Many cameras save and download their images as JPEGs. Its main drawback is its lossy format. The images below show the difference between high and low image quality.

High Quality JPEG (28K)	Low Quality JPEG (8K)
High Quality Closeup JPEG (44K)	Low Quality Closeup JPEG (4K)

GIF is commonly used for text or images with large areas without tonal transitions, such as logos. It is a lossless format that supports transparency, interlacing, and animation, so it is frequently used on the web. Its main drawback is that it only supports up to 256 colors.

TIFF is commonly used for saving flat (unlayered) files. It supports grayscale and true-color images. Although it can be compressed losslessly, its main drawback is that it results in large files, which generally prevents it from being used on the web.

PNG is a format that is intended to replace GIF and TIFF. It has the same advantages as GIF and TIFF and adds better transparency control and smaller file sizes. Its main drawback is a lack of support in certain browsers.

PSD is the native Photoshop format. It is commonly used to save layered files. Its main drawback is file size, since the files are not compressed.