When you work with digital image files, at some point we usually convert from RAW to TIFF. I choose TIFF export anytime I end up sending my images to Photoshop. The TIFF format supports both 8-bit and 16-bit color depth, layers, and Photoshop Smart Objects. The TIFF format is also open and well-documented, so most editing/viewing software can read it.
When you save a file in TIFF format from Photoshop, you get several options for compression. You can choose from no compression (uncompressed), LZW compression, or ZIP compression. ZIP compression is a newer option. I decided to take a quick look at these three saving options and see how they compared in terms of file size and saving speed.
My quick and dirty tests
I converted a 36 megapixel Nikon D800e RAW file to TIFF and opened it in Photoshop. I then saved the file with each TIFF compression mode both in 16-bit and 8-bit color. I timed how long it took to save each file to my solid-state drive. As a photographer, I’m not only interested in how big the files are, but also how long they take to save. For example, if I’m demonstrating software on my laptop, I might choose options that optimize save speed.
Results for 16-bit Files
Most often, we’ll be saving our work in a 16-bit per channel color space. As you can see, an uncompressed TIFF (no layers) from the Nikon D800e tops out at nearly 195MB. That’s a big file… the RAW (NEF) file is only about 36MB. Next, I turned on compression, and an interesting thing happened:
Not only does it take longer to save a compressed TIFF (as you might expect), but using LZW compression actually produces a file that is larger than the uncompressed original! The ZIP compression option took the longest, but reduced the file size by about 16%.
Take home message: Using LZW compression on 16-bit TIFFs is not useful. It takes longer and creates a file that’s actually 5% larger than an uncompressed file! ZIP compression is a much better option for 16-bit TIFFs, but be warned that it is a newer format that might not be supported on older software applications. Otherwise, stick with uncompressed TIFFs for the fastest save times.
Results for 8-bit files
I don’t normally work with 8-bit files, but I include them in this study as a comparison. An 8-bit TIFF from a Nikon D800e runs about 97MB, or half the size of the 16-bit file (as you might expect). I again looked at the various TIFF compression options and I also saved a copy as a JPEG (quality set to 8 in Photoshop).
Here, LZW compression works very well, indeed. The 8-bit LZW TIFF comes in at just under 38MB, a savings of nearly 62%. The ZIP file wasn’t much smaller in size compared to LZW compression. However, all of these files dwarf the JPEG, which was only 2.2 MB. However, when you look at the save speeds, it’s clear that ZIP compression of an 8-bit file is extremely slow. In fact, it took nearly a full minute to save the file!
Take home message: If your client wants an 8-bit TIFF, consider using LZW compression for a smaller file. ZIP compression takes significantly larger and doesn’t offer any additional size benefit. JPEGs are still the smallest file type, but the JPEG format doesn’t support layers.