A guide to using ZIP and LZW compression for TIFF images, along with real-world examples.
TIFF files are very high quality–much higher quality than most JPEGs–but the trade-off is that they’re big. You do, however, have some options for making them smaller by using compression. When it comes to TIFF, two main compression options are available–they’re known as LZW or ZIP.
Both ZIP and LZW are lossless compression methods. That means that no data is being lost in the compression, unlike a lossy format like JPG. You can open and save a TIFF file as many times you like without degrading the image. If you try that with JPG, the image quality will deteriorate more each time. So you can rest easy: using TIFF compression will not degrade your image quality.
The reason to use compression, whether it’s ZIP or LZW, is entirely to do with filesize. You’ll end up with files that are smaller without any loss in quality, which means quicker transfers over networks and you can fit more of them on any given amount of disk or server space. If you’re a working photographer shooting hundreds or even thousands of images a day, that can add up quickly.
There are two main reasons you might not use ZIP or LZW compression. Because they require more processing to open and close them, compressed TIFF files can be a little slower to work with. Unless you’re working with ginormous images, that’s rarely much of a problem with the speed of today’s computer processors.
A second possible reason you might not want to use ZIP or LZW compression has to do with compatibility. It is possible you might run into situations where certain software might not be able to work with compressed TIFF files. But in practice that’s pretty rare these days. Both formats have been around a long time (LZW for over 20 years and ZIP for over 10), and software developers and hardware manufacturers have had plenty of time to catch up.
There used to be a third reason not to use LZW: the algorithm was protected by patent. But that patent expired in 2003, so it’s no longer an issue for software developers to use LZW compression.
In practical use, I nearly always use compression on my TIFF files, and it’s exceedingly rare to run into a problem.
Compression algorithms are most efficient when they can group a lot of similar data. So images low on detail and with few tones will compress much more than images with lots of detail and lots of different tones.
For some real-world examples, I’ve run each of these four images through the various TIFF compression options. All are exactly the same dimensions and aspect ratio (4200px x 2800px). All have the same amount of embedded metadata (Copyright only). All have the same color profile (sRGB).
|Image #1||Image #2||Image #3||Image #4|
|8-bit No Compression||35.3 MB||35.3 MB||35.3 MB||35.3 MB|
|8-bit LZW||12.9 MB||11.5 MB||22.5 MB||12.3 MB|
|8-bit ZIP||12.6 MB||11.6 MB||20.2 MB||12.0 MB|
|16-bit No Compression||70.6 MB||70.6 MB||70.6 MB||70.6 MB|
|16-bit ZIP||54.3 MB||53.6 MB||61.9 MB||55.3 MB|
|16-bit LZW||87.0 MB||76.2 MB||87.5 MB||70.9 MB|
As you can see, image #2 (the photo of Australia’s Blue Mountains) compresses the most. It has the least detail and the fewest tones. The image that compresses least is image #3 (of the shrine offerings in Luang Prabang). It has the most detail and lots of different tones.
The last compression option, 16-bit LZW compression, is added mostly as a cautionary tale. There’s a reason you don’t have the option to export to that in Lightroom: LZW does not work at all well with 16-bit files and often makes them larger. So if you’re going to use compression on 16-bit files, stick with ZIP.
So the short answers are:
Almost certainly. It will make smaller files but will not degrade your image quality.
For 8-bit TIFF files, there’s not much in it. Both LZW and ZIP will give good results. Use either with confidence.
For 16-bit TIFF files, use ZIP.