Apple Shake 4 - Manual (Page 179)

Chapter 5 Compatible File Formats and Image Resolutions 179
To assign blind header data from one image to another:
1 Add a Copy node to the node tree, so that the nodes providing the RGBA data you
want to use are connected to the Foreground input knot.
2 Attach a second FileIn node containing the blind header information you want to use
to the Copy node’s background input knot.
3 In the Copy node’s Parameters tab, turn on the copyBData parameter.
The resulting output from the Copy node contains the blind header data from the
second FileIn node. This operation replaces any header data that was originally in the
image.