What is a clear background?
Within Prism, there is no distinction between having a clear background and a white background. Both look identical on screen.
When you paste or export a Prism graph into another program, a clear background will let colors and objects show through, so Clear is not the same as White.
The problem is that not all export formats support the concept of transparency, and Prism doesn't support all formats. The JPG, and BMP formats simply have no concept of a clear background, so those file formats simply don't allow for the possibility of clear backgrounds.
Note that Prism lets you set two separate colors for the background of a graph. What Prism calls the background is the color of the 'page'. The plotting area color is the background color within the plotting area defined by the axes. Both can be set by right clicking (control-click for mac) on the graph, or by dropping the color wheel icon. Layouts, of course, only have the page background property.
Which export formats allow you to choose a clear background?
With Prism Windows, you can choose a clear background when you export in PDF, EMF, EMF+, WMF, TIFF or PNG formats. Prism Windows cannot export EPS images with clear backgrounds (but Prism Mac can).
With Prism Mac, you can choose a clear background when you export to PDF, PNG, TIFF, and EPS format.
This choice is in the Exporting options part of the Export Graph dialog, where you can choose to include a background color or export with a clear background.
Copying graphs and layouts to the clipboard
Choose on the File & Printer tab of Preferences whether you want Prism to copy graphs and layouts to the clipboard with the background color you specified in Prism or with a clear background.
Sending to PowerPoint
Rather than copy and paste, we urge you to use the Send-to-PowerPoint command (a button at the right end of the toolbar, or a command in the File menu. The choice you make for sending background color (vs. transparent) to the clipboard (see prior section) also applies when sending a graph or layout to PowerPoint.
When you copy a graph or layout from Prism Mac, two versions are placed onto the clipboard. The PDF version supports transparent background and plotting area. Whether the background is clear or not depends on an option you set in Prism's Preference dialog (bottom of File & Printer tab). The bitmap version does not support a clear background. If you copy and paste, which version pastes depends on your version of PowerPoint and on whether you use Paste Special. Avoid the uncertainty by using the Send-to-PowerPoint command.