What kind of compression does Prism use when exporting compressed tiff files?

With TIF format, and no other, Prism lets you choose to compress the file. The advantage of compressing, of course, is that the file is smaller. The disadvantage is that compressed TIF files might be less compatible with other programs

Prism 6 Windows gives you a choice, in the Export dialog, of using no compression, LZW compression or Packbits compression. PackBits compression create the smallest file size, but LZW (Lempel-Ziv-Welch) compression might be more compatiblePrism 3 and 4 (both  Windows and Mac)  as well as Prism 5 Windows use Packbits compression and offer no other compression choice.

Prism Mac offers a checkbox to use compression when exporting tiff files. It does not offer you a choice of compression methods. It uses LZW compression when you chose Grayscale, CMYK or RGB (millions of colors, 16 bits), and PackBits compression when you choose Monochrome or RGB (256 colors, 8 bits).

Previous versions of Prism Mac included an "alpha channel" when exporting in TIFF format, and this caused problems with some journal production systems. Prism 6 does not include this alpha channel.