Today’s Question: Can you discuss the merits of LZW compression, versus ZIP [when saving a TIFF image]?
Tim’s Quick Answer: Both LZW and ZIP are lossless compression options for saving TIFF images. Both of these are lossless compression options, meaning image quality will not be degraded. The ZIP compression option will generally provide file sizes that are smaller than those with LZW compression, especially for 16-bit per channel images. In fact, with LZW compression a 16-bit per channel TIFF has the potential to be larger than the same file saved without any compression applied.
More Detail: While the compression used for JPEG images is always “lossy”, meaning image quality will be degraded even when you use the highest image quality setting, when saving TIFF images you have a couple of options that provide lossless compression.
An uncompressed TIFF file will be quite large compared to a JPEG image. A TIFF image saved with LZW or ZIP compression will still be considerably larger than the same image saved as a JPEG, but generally smaller than if compression was not used for the TIFF image.
For 8-bit per channel images you will generally get about the same degree of file size reduction when using either LZW or ZIP compression with a TIFF image. For 16-bit per channel images in most cases the file size reduction will be relatively modest with ZIP compression, and LZW compression may actually cause the file size to be larger than without the use of compression.
In theory all of this translates to a suggestion to always use ZIP compression for TIFF images, and to avoid the use of LZW compression. However, it is worth noting that not all software applications that support TIFF image files support ZIP compression for TIFF images. These days it is generally safe to use ZIP compression for TIFF images to help reduce overall file sizes, but you may want to confirm compatibility with the software you employ in your workflow before changing the settings for how you save image files.