However, which is more stable, PSD, or TIFF?
To me, TIFF ... because: * it's more likely to be supported for the duration of your grand-children's children's lifetime. * if you ever get into the position of changing pp tools away from Adobe, TIFF's are much more likely to be supported. * If Adobe ceases to exist, or decides to abandon support of PSD's, a TIFF is still likely to be supported. * My understanding is that PSD's are more complicated than TIFF's, in that a PSD is something of a "wrapper" of a tiff (as are many if not most RAW files). The PSD may be smaller than a TIFF, but my speculation is that would be because it uses a different compression algorithm. Typically, complexity == less stable. Regarding vulnerability to file corruption ... that's typically proportionally related to file size. So I suppose a smaller PSD would have a smaller risk of file corruption. Or not? Also, "consider the source" ... others on this list may inform both of us about "the error of my ways".