TIFF data volumes are influenced by the level of data compression. Approximate storage volumes: 16–80 Mb using LZW compression.
When an image is compressed, duplicated data that has no value is removed or saved in a shorter form, reducing the file’s size. For example, if large areas of water are the same tone, only the value for one pixel needs to be saved, together with the locations of the other pixels with the same colour. When the image is edited or displayed, the compression process is reversed. When a raster is compressed, not only are the data volumes reduced, but the user can download, display, edit and transfer images more quickly.
There are two forms of compression: lossless and lossy.
As its name suggests, lossless compression does not lose information within an image. A lossless compression retains the original quality of an image when it is uncompressed. This process does not provide much compression, so file sizes remain large. Lossless compression is used mainly where detail is important, such as when users are planning to make large prints.
This process degrades images to some degree, meaning that the decompressed image is not quite the same as the original. The more an image is compressed, the more degraded it becomes. In many situations, such as posting images on the Internet or printing small- to medium-sized prints, the image degradation is not so obvious. If a lossy compressed image is over enlarged, the degradation will become apparent.
TIFF is one of the most commonly used lossless image formats. TIFF is primarily designed for raster data interchange and is supported by numerous image-processing applications. This permits much more efficient access to very large files that have been compressed.