Which kinds of tiff files can Prism import.

 You can import images onto a Prism graph or layout, and Prism accepts various formats. A popular format for images is tiff, but these files can be created in many ways.

Compressed tiff files

Prism Windows (version 4 and 5) will import uncompressed TIFF images that use the RGB or gray scale color model. It cannot import compressed tiff files, or files that that use the CMYK color model. Prism Windows 6 and later can import all kinds of tiff images. 

Prism mac (version 4 or later) can import uncompressed and compressed TIFF images, as long as the compression algorithm is one of the following: LZW, PackBits, JPEG, CCITTFAX. It can import files that use either RGB or CMYK color models.

Images with alpha channel

The alpha channel encodes transparency.

Prism Mac 5 will import a tiff file that contains an alpha channel, but the results will be unsatisfactory. The image will look ok when imported, but the imported image will turn into a red X when later viewed. You can use Mac Preview (comes with OS X) to remove the alpha channel from a TIFF file.

Prism Windows 5 will not import a tiff file that contains an alpha channel, but the message it gives is misleading. The message mentions CMYK vs RGB and file compression,  but does not mention the alpha channel. 

Prism 6 and later have no problems importing tiff images with alpha channel. Some bugs were fixed in early Prism 6 releases, so if you use Prism 6, make sure you have 6.0h (mac) or 6.07 (win) or later.