If you work with graphic arts design in Photoshop and create tiff files, you probably have seen Photoshop's option to save your tiff files with or without LZW compression. What exactly is LZW compression? It is safe to use? Will LZW compression lessen the quality of your image file? Here are some answers to these valid questions...

LZW compression is a "lossless" compression format. A lot of artists and graphic designers see the word "compression" and are afraid to use it, however, "lossless" means there is NO quality loss when using it! This is not the same as jpeg compression (used mainly for web images) where there IS a loss of quality to your image file that cannot be restored. LZW compression uses an algorithm that takes reoccurring strings of data in a file and compresses them to a single string of data, therefore compressing the file. It does NOT throw away any data (like jpegs do) and if you save your TIFF file with LZW compression you can always "save as" without LZW compression later if you choose to do so.

The benefits of LZW compression -- saving space:
The main benefit for using LZW compression with TIFF files is to save space on your hard drive. LZW compression works best with images that have solid colors with not a whole lot of gradients or noise in the images and LZW compression works even better with black and white bitmapped files. For example, a 1200 dpi black and white line art file that is 15 megabytes in size uncompressed will be about 1-2 megabytes when compressed with LZW compression. With color and grayscale TIFF files I've found that you will save an average of about 30-50% with LZW compression, and in some cases you can save up to 80%. How much the file size will be reduced all depends on how much detail or gradients and noise there are in a TIFF file. For example, a 5" x 7" 300 dpi CMYK file that contains just a solid color is about 12 megabytes in size uncompressed, but with LZW compression the file will be only 55 kilabytes! There are cases in which the LZW compression may make the file bigger if there is a LOT of noise in the file. Overall, though, if you have thousands of TIFF files on your computer (as I do at my graphic arts job) using LZW compression will save you a ton of disc space.

Also, in todays world, FTP'ing files is a common way of transferring files. Using LZW compression will make your FTP uploads and downloads smaller and faster to upload or download. My personal pet peeve at my own graphic arts job is when artists upload huge uncompressed TIFF files to our FTP site and I have to wait several hours, or even several nights in some cases, to download them. For instance, one particular artist's files are mainly solid colors that are 80 megs a piece uncompressed but only 2-4 megs compressed.... and of course he uploads the huge uncompressed files. This may not be such a big deal with just a couple or a few TIFF files, but I'm talking about hundreds of 80 megabyte TIFFs... yes, for FTP uploads and downloads LZW compresion makes it much faster and easier for everyone.

Also, when writing discs backing up your files, using LZW compression can make the difference between having to burn four discs of data vs. only burning one disc.

What the detractors say about LZW compression:
If you've searched the web for answers about using LZW compression you've probably found a lot of conflicting answers. Many people say "it's safe, go ahead and use it" while many others -- professionals included -- say "it's not worth using, do not use it." Well, here are my own answers to the LZW compression detractors, based on my own eight years experience in the book publishing industry where I have worked with hundreds of thousands of TIFF files (and yes, I use LZW compression on all my files)

1) "LZW compression will not save you much space": Many detractors claim LZW compression will only save you 10% or so of space and that with today's huge hard drives space is no longer an issue. This is just hogwash. As I mentioned earlier in this article, with black and white TIFF files you can save up to 80% of space, and with color and grayscale TIFFs you can save anyhere from 10-80% depending on how much detail or noise is in the image. LZW compression is a GREAT space saver, especially when you've got thousands of TIFF files on your hard drive at any given time, as I do.

2) "LZW compressed files will not work with many programs": Many detractors claim that many graphic arts programs will not work with LZW compressed files. This may have been true ten years ago (when many of these detractor posts were written on the web) but not today. In fact, I've been using LZW compression on all my TIFF files for eight years on the job and have NEVER come across a professional graphic arts program that would not accept an LZW compressed TIFF. The programs I use and have used include Adobe Indesign, Quark Express, Pagemaker, Illustrator, and Freehand. I've never had any problems with LZW compressed TIFFs with any of these programs.

3) "Your image will lose quality with LZW compression": this is basically an old wives tale told by people who just fear the word "compression." LZW compression is "lossless" which means there is no loss of quality.

4) "LZW compression makes files open slowly": This one may have been true ten years ago on old, slow computers, but on today's machines there really is no difference -- at least as far as I can tell -- in the time it takes to open an LZW compressed TIFF file in Photoshop than an uncompressed file.

So there you go. LZW compression is a great space saver, not only on your hard drive but for burning back up discs, and FTP'ing of files. And it is completely safe to use. I give it three thumbs up. So then... why aren't you using it???